PSU Design...

On Sun, 07 May 2023 14:33:26 -0700, John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sun, 07 May 2023 18:11:53 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Sun, 07 May 2023 07:40:58 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sun, 07 May 2023 13:39:20 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Fri, 5 May 2023 06:04:43 -0700 (PDT), Anthony William Sloman
bill.sloman@ieee.org> wrote:

On Friday, May 5, 2023 at 7:39:05?PM UTC+10, piglet wrote:
On 05/05/2023 7:10 am, Anthony William Sloman wrote:

Not exactly. VR890 seems to be setting up a -9.0V reference for the dual transistor Q886 to sense, and R880,R881 and R882 divide down the -50V rail to produce a matching -9.0V but R883 (to 0V) and R884 to -53V suck out a bit of current through CR883 which complicates the situation.

If that\'s a design, I\'d hate to see an improvisation.

That\'s a really component-rich design. It was probably much-tinkered.

And not well-thought out.

CR883 would normally be reverse biased, it is there to cope with the
remote sense line getting disconnected.

I thought of that after I\'d made my post, which was a bit embarrassing. European circuit design has adopted a number of conventions that make that kind of mistake less likely.

The schematic is not drawn for great clarity but I am not critical of the design. Looks competent me and has interlocks. The use of higher voltage rails as current sources to the diff amps make it look more confusing than it is.

There are couple of PNP transistors used as current sources on the schematic, but they aren\'t drawn in a way that makes this clear.

There is a rule of thumb that says if you can\'t draw your circuit in a way that makes it clear to other people what it is doing, you probably don\'t have a clear idea of it\'s operation yourself, but American circuit diagrams from that period were pretty much uninformly horrible.

Well, I\'ve never seen anything like this before in a linear PSU from a
respected company. It\'s almost as if they were forced to use
transformers with not enough suitable secondary windings. There\'s a
revision date on this board: 1971.

Tek designed and built their own transformers. And CRTs.

\"Okay guys, we have a thousands of these transformers we designed for
the previous series and never used. We need to get rid of \'em on the
7623A, but they don\'t have enough secondary windings. See if you can
come up with an overly complex and convoluted design to overcome this
limitation. The designer who comes up with the most confusing and
tortuous configuration using the most hard-to-find components will get
a raise.\"

I charitably assume that\'s an actual quote from a Tek engineer, and
that you didn\'t make that up.

Did you ever work with any ex-Tek engineeers? I have worked with two.




Tek\'s schematics ca 1971 were brilliant and beautiful and fun.

https://w140.com/tekwiki/wiki/Tektronix_Cartoons

Imagine a draftsperson at Philips or Siemens or Oxford trying
something like that. Or even HP.

Sloman is a uniformly sour and sad old git. Ignore him.

Bill and I are around the same age. He seems to have lost his sense of
humour over the years. I\'ve clung on to mine as a survival mechanism
to cope with the fucked-up world we live in today.

The world is a pretty good place and by most indications keeps getting
better.
Click to expand...

Seriously? You must have some incredibly robust brain chemistry to be
upbeat in the face of reports like this:

https://www.zerohedge.com/news/2023-05-06/san-francisco-has-worst-downtown-recovery-rate-any-major-us-canadian-city

Every time I read ZH there\'s another story like this about California
and SF in particular. :(
 
On Sun, 7 May 2023 22:38:18 +0100, piglet <erichpwagner@hotmail.com>
wrote:

On 07/05/2023 13:39, Cursitor Doom wrote:

Well, I\'ve never seen anything like this before in a linear PSU from a
respected company. It\'s almost as if they were forced to use
transformers with not enough suitable secondary windings. There\'s a
revision date on this board: 1971.

Not sure I understand why you think there aren\'t enough secondary
windings? There is one for -/+50, one for -/+15 one for +5 and one for
80-90 which added to +50 made 130V. Seems like plenty, how would more
windings make it simpler? The 130V regulation occurring at 50V is
economical, other HV supplies of that era used that trick too.

piglet
Click to expand...

Well it\'s simple for you because you\'re an electronics wizzard, Erich.
I\'m just a humble hobbyist and \"not particularly good at electronics\"
as I describe myself. I certainly did the right thing by not taking it
up as a career, I\'m perfectly certain of that.

>Here is the service manual extract...

[snip]
Whereabouts in there did you find this, Erich?
 
On Mon, 08 May 2023 00:11:42 +0100, Cursitor Doom <cd@notformail.com>
wrote:

On Sun, 07 May 2023 14:33:26 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sun, 07 May 2023 18:11:53 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Sun, 07 May 2023 07:40:58 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sun, 07 May 2023 13:39:20 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Fri, 5 May 2023 06:04:43 -0700 (PDT), Anthony William Sloman
bill.sloman@ieee.org> wrote:

On Friday, May 5, 2023 at 7:39:05?PM UTC+10, piglet wrote:
On 05/05/2023 7:10 am, Anthony William Sloman wrote:

Not exactly. VR890 seems to be setting up a -9.0V reference for the dual transistor Q886 to sense, and R880,R881 and R882 divide down the -50V rail to produce a matching -9.0V but R883 (to 0V) and R884 to -53V suck out a bit of current through CR883 which complicates the situation.

If that\'s a design, I\'d hate to see an improvisation.

That\'s a really component-rich design. It was probably much-tinkered.

And not well-thought out.

CR883 would normally be reverse biased, it is there to cope with the
remote sense line getting disconnected.

I thought of that after I\'d made my post, which was a bit embarrassing. European circuit design has adopted a number of conventions that make that kind of mistake less likely.

The schematic is not drawn for great clarity but I am not critical of the design. Looks competent me and has interlocks. The use of higher voltage rails as current sources to the diff amps make it look more confusing than it is.

There are couple of PNP transistors used as current sources on the schematic, but they aren\'t drawn in a way that makes this clear.

There is a rule of thumb that says if you can\'t draw your circuit in a way that makes it clear to other people what it is doing, you probably don\'t have a clear idea of it\'s operation yourself, but American circuit diagrams from that period were pretty much uninformly horrible.

Well, I\'ve never seen anything like this before in a linear PSU from a
respected company. It\'s almost as if they were forced to use
transformers with not enough suitable secondary windings. There\'s a
revision date on this board: 1971.

Tek designed and built their own transformers. And CRTs.

\"Okay guys, we have a thousands of these transformers we designed for
the previous series and never used. We need to get rid of \'em on the
7623A, but they don\'t have enough secondary windings. See if you can
come up with an overly complex and convoluted design to overcome this
limitation. The designer who comes up with the most confusing and
tortuous configuration using the most hard-to-find components will get
a raise.\"

I charitably assume that\'s an actual quote from a Tek engineer, and
that you didn\'t make that up.

Did you ever work with any ex-Tek engineeers? I have worked with two.




Tek\'s schematics ca 1971 were brilliant and beautiful and fun.

https://w140.com/tekwiki/wiki/Tektronix_Cartoons

Imagine a draftsperson at Philips or Siemens or Oxford trying
something like that. Or even HP.

Sloman is a uniformly sour and sad old git. Ignore him.

Bill and I are around the same age. He seems to have lost his sense of
humour over the years. I\'ve clung on to mine as a survival mechanism
to cope with the fucked-up world we live in today.

The world is a pretty good place and by most indications keeps getting
better.

Seriously? You must have some incredibly robust brain chemistry to be
upbeat in the face of reports like this:

https://www.zerohedge.com/news/2023-05-06/san-francisco-has-worst-downtown-recovery-rate-any-major-us-canadian-city

Every time I read ZH there\'s another story like this about California
and SF in particular. :(
Click to expand...

Downtown is pretty ratty, full of homeless and tourists; we don\'t go
there.

But SF has a low overall crime rate, especially away from downtown,
and it\'s beautiful and full of nice people.

Worldwide, life spans are up, poverty is down, food production is
soaring, birth rates are leveling off. Ignore the news: if it bleeds,
it leads.
 
On 08/05/2023 00:23, Cursitor Doom wrote:
On Sun, 7 May 2023 22:38:18 +0100, piglet <erichpwagner@hotmail.com
wrote:

On 07/05/2023 13:39, Cursitor Doom wrote:

Well, I\'ve never seen anything like this before in a linear PSU from a
respected company. It\'s almost as if they were forced to use
transformers with not enough suitable secondary windings. There\'s a
revision date on this board: 1971.

Not sure I understand why you think there aren\'t enough secondary
windings? There is one for -/+50, one for -/+15 one for +5 and one for
80-90 which added to +50 made 130V. Seems like plenty, how would more
windings make it simpler? The 130V regulation occurring at 50V is
economical, other HV supplies of that era used that trick too.

piglet

Well it\'s simple for you because you\'re an electronics wizzard, Erich.
I\'m just a humble hobbyist and \"not particularly good at electronics\"
as I describe myself. I certainly did the right thing by not taking it
up as a career, I\'m perfectly certain of that.

Here is the service manual extract...

[snip]
Whereabouts in there did you find this, Erich?
Click to expand...

Page 3-27 of the 7623 service manual at Tekwiki

piglet
 
On Monday, May 8, 2023 at 7:33:43 AM UTC+10, John Larkin wrote:
On Sun, 07 May 2023 18:11:53 +0100, Cursitor Doom <c...@notformail.com> wrote:
On Sun, 07 May 2023 07:40:58 -0700, John Larkin <jla...@highlandSNIPMEtechnology.com> wrote:
On Sun, 07 May 2023 13:39:20 +0100, Cursitor Doom <c...@notformail.com> wrote:
On Fri, 5 May 2023 06:04:43 -0700 (PDT), Anthony William Sloman <bill.....@ieee.org> wrote:
On Friday, May 5, 2023 at 7:39:05?PM UTC+10, piglet wrote:
On 05/05/2023 7:10 am, Anthony William Sloman wrote:

\"Okay guys, we have a thousands of these transformers we designed for
the previous series and never used. We need to get rid of \'em on the
7623A, but they don\'t have enough secondary windings. See if you can
come up with an overly complex and convoluted design to overcome this
limitation. The designer who comes up with the most confusing and
tortuous configuration using the most hard-to-find components will get
a raise.\"
Click to expand...

Cursitor Doom does try to be satirical from time to time - he likes to pretend that he has a sense of humour, but what it does illustrate is his tin ear.

> I charitably assume that\'s an actual quote from a Tek engineer, and that you didn\'t make that up.

There\'s nothing charitable in that assumption - it is simply moronic.

> Did you ever work with any ex-Tek engineeers? I have worked with two.

Did they get fired after they\'d worked with you, or was the sloppy habits that got them fired that let them work with you?

<snip>

> The world is a pretty good place and by most indications keeps getting better.

Ask any Pollyanna who is a sucker for climate change denial propaganda.

--
Bill Sloman, Sydney
 
On Sun, 07 May 2023 18:39:43 -0700, John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote:

On Mon, 08 May 2023 00:11:42 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Sun, 07 May 2023 14:33:26 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sun, 07 May 2023 18:11:53 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Sun, 07 May 2023 07:40:58 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sun, 07 May 2023 13:39:20 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Fri, 5 May 2023 06:04:43 -0700 (PDT), Anthony William Sloman
bill.sloman@ieee.org> wrote:

On Friday, May 5, 2023 at 7:39:05?PM UTC+10, piglet wrote:
On 05/05/2023 7:10 am, Anthony William Sloman wrote:

Not exactly. VR890 seems to be setting up a -9.0V reference for the dual transistor Q886 to sense, and R880,R881 and R882 divide down the -50V rail to produce a matching -9.0V but R883 (to 0V) and R884 to -53V suck out a bit of current through CR883 which complicates the situation.

If that\'s a design, I\'d hate to see an improvisation.

That\'s a really component-rich design. It was probably much-tinkered.

And not well-thought out.

CR883 would normally be reverse biased, it is there to cope with the
remote sense line getting disconnected.

I thought of that after I\'d made my post, which was a bit embarrassing. European circuit design has adopted a number of conventions that make that kind of mistake less likely.

The schematic is not drawn for great clarity but I am not critical of the design. Looks competent me and has interlocks. The use of higher voltage rails as current sources to the diff amps make it look more confusing than it is.

There are couple of PNP transistors used as current sources on the schematic, but they aren\'t drawn in a way that makes this clear.

There is a rule of thumb that says if you can\'t draw your circuit in a way that makes it clear to other people what it is doing, you probably don\'t have a clear idea of it\'s operation yourself, but American circuit diagrams from that period were pretty much uninformly horrible.

Well, I\'ve never seen anything like this before in a linear PSU from a
respected company. It\'s almost as if they were forced to use
transformers with not enough suitable secondary windings. There\'s a
revision date on this board: 1971.

Tek designed and built their own transformers. And CRTs.

\"Okay guys, we have a thousands of these transformers we designed for
the previous series and never used. We need to get rid of \'em on the
7623A, but they don\'t have enough secondary windings. See if you can
come up with an overly complex and convoluted design to overcome this
limitation. The designer who comes up with the most confusing and
tortuous configuration using the most hard-to-find components will get
a raise.\"

I charitably assume that\'s an actual quote from a Tek engineer, and
that you didn\'t make that up.

Did you ever work with any ex-Tek engineeers? I have worked with two.




Tek\'s schematics ca 1971 were brilliant and beautiful and fun.

https://w140.com/tekwiki/wiki/Tektronix_Cartoons

Imagine a draftsperson at Philips or Siemens or Oxford trying
something like that. Or even HP.

Sloman is a uniformly sour and sad old git. Ignore him.

Bill and I are around the same age. He seems to have lost his sense of
humour over the years. I\'ve clung on to mine as a survival mechanism
to cope with the fucked-up world we live in today.

The world is a pretty good place and by most indications keeps getting
better.

Seriously? You must have some incredibly robust brain chemistry to be
upbeat in the face of reports like this:

https://www.zerohedge.com/news/2023-05-06/san-francisco-has-worst-downtown-recovery-rate-any-major-us-canadian-city

Every time I read ZH there\'s another story like this about California
and SF in particular. :(

Downtown is pretty ratty, full of homeless and tourists; we don\'t go
there.
Click to expand...

No one with any sense would. I\'ve seen the pictures. This is the
consequence of many years of Socialist policies.


But SF has a low overall crime rate, especially away from downtown,
and it\'s beautiful and full of nice people.
Click to expand...

Do they still wear flowers in their hair?
I assume you can recommend some amazingly effective antidepressents.
May I know the name(s) of them? (Asking for a friend). :)
 
On Mon, 8 May 2023 07:18:58 +0100, piglet <erichpwagner@hotmail.com>
wrote:

On 08/05/2023 00:23, Cursitor Doom wrote:
On Sun, 7 May 2023 22:38:18 +0100, piglet <erichpwagner@hotmail.com
wrote:

On 07/05/2023 13:39, Cursitor Doom wrote:

Well, I\'ve never seen anything like this before in a linear PSU from a
respected company. It\'s almost as if they were forced to use
transformers with not enough suitable secondary windings. There\'s a
revision date on this board: 1971.

Not sure I understand why you think there aren\'t enough secondary
windings? There is one for -/+50, one for -/+15 one for +5 and one for
80-90 which added to +50 made 130V. Seems like plenty, how would more
windings make it simpler? The 130V regulation occurring at 50V is
economical, other HV supplies of that era used that trick too.

piglet

Well it\'s simple for you because you\'re an electronics wizzard, Erich.
I\'m just a humble hobbyist and \"not particularly good at electronics\"
as I describe myself. I certainly did the right thing by not taking it
up as a career, I\'m perfectly certain of that.

Here is the service manual extract...

[snip]
Whereabouts in there did you find this, Erich?




Page 3-27 of the 7623 service manual at Tekwiki

piglet
Click to expand...

Argh! Tekwiki - I\'d forgotten all about that particular resource. Many
thanks indeed.
 
On Mon, 08 May 2023 09:44:01 +0100, Cursitor Doom <cd@notformail.com>
wrote:

On Sun, 07 May 2023 18:39:43 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Mon, 08 May 2023 00:11:42 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Sun, 07 May 2023 14:33:26 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sun, 07 May 2023 18:11:53 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Sun, 07 May 2023 07:40:58 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sun, 07 May 2023 13:39:20 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Fri, 5 May 2023 06:04:43 -0700 (PDT), Anthony William Sloman
bill.sloman@ieee.org> wrote:

On Friday, May 5, 2023 at 7:39:05?PM UTC+10, piglet wrote:
On 05/05/2023 7:10 am, Anthony William Sloman wrote:

Not exactly. VR890 seems to be setting up a -9.0V reference for the dual transistor Q886 to sense, and R880,R881 and R882 divide down the -50V rail to produce a matching -9.0V but R883 (to 0V) and R884 to -53V suck out a bit of current through CR883 which complicates the situation.

If that\'s a design, I\'d hate to see an improvisation.

That\'s a really component-rich design. It was probably much-tinkered.

And not well-thought out.

CR883 would normally be reverse biased, it is there to cope with the
remote sense line getting disconnected.

I thought of that after I\'d made my post, which was a bit embarrassing. European circuit design has adopted a number of conventions that make that kind of mistake less likely.

The schematic is not drawn for great clarity but I am not critical of the design. Looks competent me and has interlocks. The use of higher voltage rails as current sources to the diff amps make it look more confusing than it is.

There are couple of PNP transistors used as current sources on the schematic, but they aren\'t drawn in a way that makes this clear.

There is a rule of thumb that says if you can\'t draw your circuit in a way that makes it clear to other people what it is doing, you probably don\'t have a clear idea of it\'s operation yourself, but American circuit diagrams from that period were pretty much uninformly horrible.

Well, I\'ve never seen anything like this before in a linear PSU from a
respected company. It\'s almost as if they were forced to use
transformers with not enough suitable secondary windings. There\'s a
revision date on this board: 1971.

Tek designed and built their own transformers. And CRTs.

\"Okay guys, we have a thousands of these transformers we designed for
the previous series and never used. We need to get rid of \'em on the
7623A, but they don\'t have enough secondary windings. See if you can
come up with an overly complex and convoluted design to overcome this
limitation. The designer who comes up with the most confusing and
tortuous configuration using the most hard-to-find components will get
a raise.\"

I charitably assume that\'s an actual quote from a Tek engineer, and
that you didn\'t make that up.

Did you ever work with any ex-Tek engineeers? I have worked with two.




Tek\'s schematics ca 1971 were brilliant and beautiful and fun.

https://w140.com/tekwiki/wiki/Tektronix_Cartoons

Imagine a draftsperson at Philips or Siemens or Oxford trying
something like that. Or even HP.

Sloman is a uniformly sour and sad old git. Ignore him.

Bill and I are around the same age. He seems to have lost his sense of
humour over the years. I\'ve clung on to mine as a survival mechanism
to cope with the fucked-up world we live in today.

The world is a pretty good place and by most indications keeps getting
better.

Seriously? You must have some incredibly robust brain chemistry to be
upbeat in the face of reports like this:

https://www.zerohedge.com/news/2023-05-06/san-francisco-has-worst-downtown-recovery-rate-any-major-us-canadian-city

Every time I read ZH there\'s another story like this about California
and SF in particular. :(

Downtown is pretty ratty, full of homeless and tourists; we don\'t go
there.

No one with any sense would. I\'ve seen the pictures. This is the
consequence of many years of Socialist policies.
Click to expand...

The pictures are not representative of much of the city. Even Paradise
must have a city dump.

But visitors don\'t often see the cool and beautiful stuff here, so you
should stay away. Walk across the Golden Gate Bridge, check out a few
quirky streets, and drive on. Staying in a crazy expensive downtown
tourist hotel is silly.

We\'re still discovering stuff.

But SF has a low overall crime rate, especially away from downtown,
and it\'s beautiful and full of nice people.

Do they still wear flowers in their hair?
Click to expand...

I don\'t. The hippie thing was just another form of tourism, but
pathological. Hippies can\'t afford to live here now.

I assume you can recommend some amazingly effective antidepressents.
May I know the name(s) of them? (Asking for a friend). :)
Click to expand...

No. Personally, so far, getting exercize (hiking San Francisco!) and
keeping my weight down is working. Designing things keeps me happy
too. Is your friend deep depressed or bipolar?
 
On Mon, 08 May 2023 00:23:58 +0100, Cursitor Doom <cd@notformail.com>
wrote:

On Sun, 7 May 2023 22:38:18 +0100, piglet <erichpwagner@hotmail.com
wrote:

On 07/05/2023 13:39, Cursitor Doom wrote:

Well, I\'ve never seen anything like this before in a linear PSU from a
respected company. It\'s almost as if they were forced to use
transformers with not enough suitable secondary windings. There\'s a
revision date on this board: 1971.

Not sure I understand why you think there aren\'t enough secondary
windings? There is one for -/+50, one for -/+15 one for +5 and one for
80-90 which added to +50 made 130V. Seems like plenty, how would more
windings make it simpler? The 130V regulation occurring at 50V is
economical, other HV supplies of that era used that trick too.

piglet

Well it\'s simple for you because you\'re an electronics wizzard, Erich.
I\'m just a humble hobbyist and \"not particularly good at electronics\"
as I describe myself. I certainly did the right thing by not taking it
up as a career, I\'m perfectly certain of that.
Click to expand...

Well, that Tek schamatic is kind of a tangle. Not at all obvious on
first sight.

Maybe you\'re not autistic enough to be very good at electronics
design.
 
On Mon, 08 May 2023 04:39:11 -0700, John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote:

On Mon, 08 May 2023 09:44:01 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Sun, 07 May 2023 18:39:43 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Mon, 08 May 2023 00:11:42 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Sun, 07 May 2023 14:33:26 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sun, 07 May 2023 18:11:53 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Sun, 07 May 2023 07:40:58 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sun, 07 May 2023 13:39:20 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Fri, 5 May 2023 06:04:43 -0700 (PDT), Anthony William Sloman
bill.sloman@ieee.org> wrote:

On Friday, May 5, 2023 at 7:39:05?PM UTC+10, piglet wrote:
On 05/05/2023 7:10 am, Anthony William Sloman wrote:

Not exactly. VR890 seems to be setting up a -9.0V reference for the dual transistor Q886 to sense, and R880,R881 and R882 divide down the -50V rail to produce a matching -9.0V but R883 (to 0V) and R884 to -53V suck out a bit of current through CR883 which complicates the situation.

If that\'s a design, I\'d hate to see an improvisation.

That\'s a really component-rich design. It was probably much-tinkered.

And not well-thought out.

CR883 would normally be reverse biased, it is there to cope with the
remote sense line getting disconnected.

I thought of that after I\'d made my post, which was a bit embarrassing. European circuit design has adopted a number of conventions that make that kind of mistake less likely.

The schematic is not drawn for great clarity but I am not critical of the design. Looks competent me and has interlocks. The use of higher voltage rails as current sources to the diff amps make it look more confusing than it is.

There are couple of PNP transistors used as current sources on the schematic, but they aren\'t drawn in a way that makes this clear.

There is a rule of thumb that says if you can\'t draw your circuit in a way that makes it clear to other people what it is doing, you probably don\'t have a clear idea of it\'s operation yourself, but American circuit diagrams from that period were pretty much uninformly horrible.

Well, I\'ve never seen anything like this before in a linear PSU from a
respected company. It\'s almost as if they were forced to use
transformers with not enough suitable secondary windings. There\'s a
revision date on this board: 1971.

Tek designed and built their own transformers. And CRTs.

\"Okay guys, we have a thousands of these transformers we designed for
the previous series and never used. We need to get rid of \'em on the
7623A, but they don\'t have enough secondary windings. See if you can
come up with an overly complex and convoluted design to overcome this
limitation. The designer who comes up with the most confusing and
tortuous configuration using the most hard-to-find components will get
a raise.\"

I charitably assume that\'s an actual quote from a Tek engineer, and
that you didn\'t make that up.

Did you ever work with any ex-Tek engineeers? I have worked with two.




Tek\'s schematics ca 1971 were brilliant and beautiful and fun.

https://w140.com/tekwiki/wiki/Tektronix_Cartoons

Imagine a draftsperson at Philips or Siemens or Oxford trying
something like that. Or even HP.

Sloman is a uniformly sour and sad old git. Ignore him.

Bill and I are around the same age. He seems to have lost his sense of
humour over the years. I\'ve clung on to mine as a survival mechanism
to cope with the fucked-up world we live in today.

The world is a pretty good place and by most indications keeps getting
better.

Seriously? You must have some incredibly robust brain chemistry to be
upbeat in the face of reports like this:

https://www.zerohedge.com/news/2023-05-06/san-francisco-has-worst-downtown-recovery-rate-any-major-us-canadian-city

Every time I read ZH there\'s another story like this about California
and SF in particular. :(

Downtown is pretty ratty, full of homeless and tourists; we don\'t go
there.

No one with any sense would. I\'ve seen the pictures. This is the
consequence of many years of Socialist policies.

The pictures are not representative of much of the city. Even Paradise
must have a city dump.

But visitors don\'t often see the cool and beautiful stuff here, so you
should stay away. Walk across the Golden Gate Bridge, check out a few
quirky streets, and drive on. Staying in a crazy expensive downtown
tourist hotel is silly.

We\'re still discovering stuff.



But SF has a low overall crime rate, especially away from downtown,
and it\'s beautiful and full of nice people.

Do they still wear flowers in their hair?

I don\'t. The hippie thing was just another form of tourism, but
pathological. Hippies can\'t afford to live here now.

I assume you can recommend some amazingly effective antidepressents.
May I know the name(s) of them? (Asking for a friend). :)

No. Personally, so far, getting exercize (hiking San Francisco!) and
keeping my weight down is working. Designing things keeps me happy
too. Is your friend deep depressed or bipolar?
Click to expand...

Early \'days\' so far, but looks like Bipolar and possibly type 2. She\'s
not responding very well to the current regime (some combo of
Quetiapine and Pregabalin). I told her to go back to the dox and ask
about switching to Lithium, which as you will know was the go-to med
of first choice back in the day (and presumably is still available).
Your thoughts?
 
On Mon, 08 May 2023 04:43:24 -0700, John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote:

On Mon, 08 May 2023 00:23:58 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Sun, 7 May 2023 22:38:18 +0100, piglet <erichpwagner@hotmail.com
wrote:

On 07/05/2023 13:39, Cursitor Doom wrote:

Well, I\'ve never seen anything like this before in a linear PSU from a
respected company. It\'s almost as if they were forced to use
transformers with not enough suitable secondary windings. There\'s a
revision date on this board: 1971.

Not sure I understand why you think there aren\'t enough secondary
windings? There is one for -/+50, one for -/+15 one for +5 and one for
80-90 which added to +50 made 130V. Seems like plenty, how would more
windings make it simpler? The 130V regulation occurring at 50V is
economical, other HV supplies of that era used that trick too.

piglet

Well it\'s simple for you because you\'re an electronics wizzard, Erich.
I\'m just a humble hobbyist and \"not particularly good at electronics\"
as I describe myself. I certainly did the right thing by not taking it
up as a career, I\'m perfectly certain of that.

Well, that Tek schamatic is kind of a tangle. Not at all obvious on
first sight.
Click to expand...

I\'ve been chatting to some chap on another forum who\'s repaired
several of these boards and he agrees. They\'re a pain in the arse
having those interdependencies and I don\'t care what the venerable
piglet says to the contrary.

Maybe you\'re not autistic enough to be very good at electronics
design.
Click to expand...

I just find it fascinating how different people excell at certain
things, but are useless at others. It\'s a source of infinite wonder to
me.
 
On Monday, May 8, 2023 at 9:43:46 PM UTC+10, John Larkin wrote:
On Mon, 08 May 2023 00:23:58 +0100, Cursitor Doom <c...@notformail.com
wrote:
On Sun, 7 May 2023 22:38:18 +0100, piglet <erichp...@hotmail.com
wrote:

On 07/05/2023 13:39, Cursitor Doom wrote:

Well, I\'ve never seen anything like this before in a linear PSU from a
respected company. It\'s almost as if they were forced to use
transformers with not enough suitable secondary windings. There\'s a
revision date on this board: 1971.

Not sure I understand why you think there aren\'t enough secondary
windings? There is one for -/+50, one for -/+15 one for +5 and one for
80-90 which added to +50 made 130V. Seems like plenty, how would more
windings make it simpler? The 130V regulation occurring at 50V is
economical, other HV supplies of that era used that trick too.

Well it\'s simple for you because you\'re an electronics wizzard, Erich.
I\'m just a humble hobbyist and \"not particularly good at electronics\"
as I describe myself. I certainly did the right thing by not taking it
up as a career, I\'m perfectly certain of that.

Well, that Tek schematic is kind of a tangle. Not at all obvious on first sight.
Click to expand...

It does take quite a lot of untangling.

> Maybe you\'re not autistic enough to be very good at electronics design.

Autism is about problems with social interaction. There\'s a popular delusion that if you don\'t use up brain power on interacting with other people, you got more to spare to devote to thinking about inanimate objects, but it\'s just more pop-psychology twaddle. The good electronic designers I interacted with were perfectly fine at interacting with other people, and they have to be because what they design has got to be useful to other people. The marketing clowns that sold the products weren\'t as good and had a tendency to warp the designs in ways that made the product easier to sell, rather than easier to use, and more reliable in use.

--
Bill Sloman, Sydney
 
On Monday, May 8, 2023 at 10:04:18 PM UTC+10, Cursitor Doom wrote:
On Mon, 08 May 2023 04:43:24 -0700, John Larkin <jla...@highlandSNIPMEtechnology.com> wrote:
On Mon, 08 May 2023 00:23:58 +0100, Cursitor Doom <c...@notformail.com> wrote:
On Sun, 7 May 2023 22:38:18 +0100, piglet <erichp...@hotmail.com> wrote:
On 07/05/2023 13:39, Cursitor Doom wrote:
Click to expand...

<snip>

Well, that Tek schamatic is kind of a tangle. Not at all obvious on first sight.

I\'ve been chatting to some chap on another forum who\'s repaired several of these boards and he agrees. They\'re a pain in the arse
having those interdependencies and I don\'t care what the venerable piglet says to the contrary.
Click to expand...

I course you don\'t. You are an ignorant idiot. Piglet is one of the more exalted electronic gurus who post here, but you don\';t know enough to realise that.

Maybe you\'re not autistic enough to be very good at electronics design.

I just find it fascinating how different people excel at certain things, but are useless at others. It\'s a source of infinite wonder to me.
Click to expand...

If you showed any sign of excelling at anything - gullibility isn\'t a skill even if you have specialised in it - you might find it less wonderful.

--
Bill Sloman, Sydney
 
On Mon, 08 May 2023 13:00:40 +0100, Cursitor Doom <cd@notformail.com>
wrote:

On Mon, 08 May 2023 04:39:11 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Mon, 08 May 2023 09:44:01 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Sun, 07 May 2023 18:39:43 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Mon, 08 May 2023 00:11:42 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Sun, 07 May 2023 14:33:26 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sun, 07 May 2023 18:11:53 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Sun, 07 May 2023 07:40:58 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sun, 07 May 2023 13:39:20 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Fri, 5 May 2023 06:04:43 -0700 (PDT), Anthony William Sloman
bill.sloman@ieee.org> wrote:

On Friday, May 5, 2023 at 7:39:05?PM UTC+10, piglet wrote:
On 05/05/2023 7:10 am, Anthony William Sloman wrote:

Not exactly. VR890 seems to be setting up a -9.0V reference for the dual transistor Q886 to sense, and R880,R881 and R882 divide down the -50V rail to produce a matching -9.0V but R883 (to 0V) and R884 to -53V suck out a bit of current through CR883 which complicates the situation.

If that\'s a design, I\'d hate to see an improvisation.

That\'s a really component-rich design. It was probably much-tinkered.

And not well-thought out.

CR883 would normally be reverse biased, it is there to cope with the
remote sense line getting disconnected.

I thought of that after I\'d made my post, which was a bit embarrassing. European circuit design has adopted a number of conventions that make that kind of mistake less likely.

The schematic is not drawn for great clarity but I am not critical of the design. Looks competent me and has interlocks. The use of higher voltage rails as current sources to the diff amps make it look more confusing than it is.

There are couple of PNP transistors used as current sources on the schematic, but they aren\'t drawn in a way that makes this clear.

There is a rule of thumb that says if you can\'t draw your circuit in a way that makes it clear to other people what it is doing, you probably don\'t have a clear idea of it\'s operation yourself, but American circuit diagrams from that period were pretty much uninformly horrible.

Well, I\'ve never seen anything like this before in a linear PSU from a
respected company. It\'s almost as if they were forced to use
transformers with not enough suitable secondary windings. There\'s a
revision date on this board: 1971.

Tek designed and built their own transformers. And CRTs.

\"Okay guys, we have a thousands of these transformers we designed for
the previous series and never used. We need to get rid of \'em on the
7623A, but they don\'t have enough secondary windings. See if you can
come up with an overly complex and convoluted design to overcome this
limitation. The designer who comes up with the most confusing and
tortuous configuration using the most hard-to-find components will get
a raise.\"

I charitably assume that\'s an actual quote from a Tek engineer, and
that you didn\'t make that up.

Did you ever work with any ex-Tek engineeers? I have worked with two.




Tek\'s schematics ca 1971 were brilliant and beautiful and fun.

https://w140.com/tekwiki/wiki/Tektronix_Cartoons

Imagine a draftsperson at Philips or Siemens or Oxford trying
something like that. Or even HP.

Sloman is a uniformly sour and sad old git. Ignore him.

Bill and I are around the same age. He seems to have lost his sense of
humour over the years. I\'ve clung on to mine as a survival mechanism
to cope with the fucked-up world we live in today.

The world is a pretty good place and by most indications keeps getting
better.

Seriously? You must have some incredibly robust brain chemistry to be
upbeat in the face of reports like this:

https://www.zerohedge.com/news/2023-05-06/san-francisco-has-worst-downtown-recovery-rate-any-major-us-canadian-city

Every time I read ZH there\'s another story like this about California
and SF in particular. :(

Downtown is pretty ratty, full of homeless and tourists; we don\'t go
there.

No one with any sense would. I\'ve seen the pictures. This is the
consequence of many years of Socialist policies.

The pictures are not representative of much of the city. Even Paradise
must have a city dump.

But visitors don\'t often see the cool and beautiful stuff here, so you
should stay away. Walk across the Golden Gate Bridge, check out a few
quirky streets, and drive on. Staying in a crazy expensive downtown
tourist hotel is silly.

We\'re still discovering stuff.



But SF has a low overall crime rate, especially away from downtown,
and it\'s beautiful and full of nice people.

Do they still wear flowers in their hair?

I don\'t. The hippie thing was just another form of tourism, but
pathological. Hippies can\'t afford to live here now.

I assume you can recommend some amazingly effective antidepressents.
May I know the name(s) of them? (Asking for a friend). :)

No. Personally, so far, getting exercize (hiking San Francisco!) and
keeping my weight down is working. Designing things keeps me happy
too. Is your friend deep depressed or bipolar?

Early \'days\' so far, but looks like Bipolar and possibly type 2. She\'s
not responding very well to the current regime (some combo of
Quetiapine and Pregabalin). I told her to go back to the dox and ask
about switching to Lithium, which as you will know was the go-to med
of first choice back in the day (and presumably is still available).
Your thoughts?
Click to expand...

I couldn\'t say anything useful, but to observe that drugs have side
effects.

So many people are unhappy.
 
On Mon, 08 May 2023 13:04:10 +0100, Cursitor Doom <cd@notformail.com>
wrote:

On Mon, 08 May 2023 04:43:24 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Mon, 08 May 2023 00:23:58 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Sun, 7 May 2023 22:38:18 +0100, piglet <erichpwagner@hotmail.com
wrote:

On 07/05/2023 13:39, Cursitor Doom wrote:

Well, I\'ve never seen anything like this before in a linear PSU from a
respected company. It\'s almost as if they were forced to use
transformers with not enough suitable secondary windings. There\'s a
revision date on this board: 1971.

Not sure I understand why you think there aren\'t enough secondary
windings? There is one for -/+50, one for -/+15 one for +5 and one for
80-90 which added to +50 made 130V. Seems like plenty, how would more
windings make it simpler? The 130V regulation occurring at 50V is
economical, other HV supplies of that era used that trick too.

piglet

Well it\'s simple for you because you\'re an electronics wizzard, Erich.
I\'m just a humble hobbyist and \"not particularly good at electronics\"
as I describe myself. I certainly did the right thing by not taking it
up as a career, I\'m perfectly certain of that.

Well, that Tek schamatic is kind of a tangle. Not at all obvious on
first sight.

I\'ve been chatting to some chap on another forum who\'s repaired
several of these boards and he agrees. They\'re a pain in the arse
having those interdependencies and I don\'t care what the venerable
piglet says to the contrary.


Maybe you\'re not autistic enough to be very good at electronics
design.

I just find it fascinating how different people excell at certain
things, but are useless at others. It\'s a source of infinite wonder to
me.
Click to expand...

Humans sure specialize. I think that, in a tribe, some people grow
food, some make arrows, and some shoot arrows. Cows and oysters don\'t
seem to specialize as much.

What fascinates me is how humans, hunter-gatherers, evolved to be able
to do calculus and design electronics.
 
On 08/05/2023 13:04, Cursitor Doom wrote:
I\'ve been chatting to some chap on another forum who\'s repaired
several of these boards and he agrees. They\'re a pain in the arse
having those interdependencies and I don\'t care what the venerable
piglet says to the contrary.
Click to expand...

Haha, thanks for the accolade!

Yes, there are interactions. At a guess I\'d suggest first making
something come out the +130V pin, doesn\'t need to 130 yet, even 60-80V
would do. Then work on getting the -50V section working, all the rest
are keyed to that. Next the +50V regulator, then recheck the 130V is now
right. Then -15V, then +15, lastly +5V and then go back and recheck all.
Then reconnect to rest of the scope and see what happens.

the venerable piglet
 
On Monday, May 8, 2023 at 10:02:54 PM UTC+10, Cursitor Doom wrote:
On Mon, 08 May 2023 04:39:11 -0700, John Larkin <jla...@highlandSNIPMEtechnology.com> wrote:
On Mon, 08 May 2023 09:44:01 +0100, Cursitor Doom <c...@notformail.com> wrote:
On Sun, 07 May 2023 18:39:43 -0700, John Larkin <jla...@highlandSNIPMEtechnology.com> wrote:
On Mon, 08 May 2023 00:11:42 +0100, Cursitor Doom <c...@notformail.com> wrote:
On Sun, 07 May 2023 14:33:26 -0700, John Larkin <jla...@highlandSNIPMEtechnology.com> wrote:
On Sun, 07 May 2023 18:11:53 +0100, Cursitor Doom <c...@notformail.com> wrote:
On Sun, 07 May 2023 07:40:58 -0700, John Larkin <jla...@highlandSNIPMEtechnology.com> wrote:
On Sun, 07 May 2023 13:39:20 +0100, Cursitor Doom <c...@notformail..com> wrote:
On Fri, 5 May 2023 06:04:43 -0700 (PDT), Anthony William Sloman <bill....@ieee.org> wrote:
On Friday, May 5, 2023 at 7:39:05?PM UTC+10, piglet wrote:
On 05/05/2023 7:10 am, Anthony William Sloman wrote:
Click to expand...

<snip>

I assume you can recommend some amazingly effective antidepressents.
May I know the name(s) of them? (Asking for a friend). :)

No. Personally, so far, getting exercize (hiking San Francisco!) and
keeping my weight down is working. Designing things keeps me happy
too. Is your friend deep depressed or bipolar?
Early \'days\' so far, but looks like Bipolar and possibly type 2. She\'s
not responding very well to the current regime (some combo of
Quetiapine and Pregabalin). I told her to go back to the dox and ask
about switching to Lithium, which as you will know was the go-to med
of first choice back in the day (and presumably is still available).

Your thoughts?
Click to expand...

Lithium is very specific to bipolar. One of my cousins did his Ph.D. on it\'s use back when I was doing mine.

My only bipolar friend won\'t use it because he likes being manic - when it happens.

--
Bill Sloman, Sydney
 
On Mon, 8 May 2023 05:36:08 -0700 (PDT), Anthony William Sloman
<bill.sloman@ieee.org> wrote:

On Monday, May 8, 2023 at 10:02:54?PM UTC+10, Cursitor Doom wrote:
On Mon, 08 May 2023 04:39:11 -0700, John Larkin <jla...@highlandSNIPMEtechnology.com> wrote:
On Mon, 08 May 2023 09:44:01 +0100, Cursitor Doom <c...@notformail.com> wrote:
On Sun, 07 May 2023 18:39:43 -0700, John Larkin <jla...@highlandSNIPMEtechnology.com> wrote:
On Mon, 08 May 2023 00:11:42 +0100, Cursitor Doom <c...@notformail.com> wrote:
On Sun, 07 May 2023 14:33:26 -0700, John Larkin <jla...@highlandSNIPMEtechnology.com> wrote:
On Sun, 07 May 2023 18:11:53 +0100, Cursitor Doom <c...@notformail.com> wrote:
On Sun, 07 May 2023 07:40:58 -0700, John Larkin <jla...@highlandSNIPMEtechnology.com> wrote:
On Sun, 07 May 2023 13:39:20 +0100, Cursitor Doom <c...@notformail.com> wrote:
On Fri, 5 May 2023 06:04:43 -0700 (PDT), Anthony William Sloman <bill....@ieee.org> wrote:
On Friday, May 5, 2023 at 7:39:05?PM UTC+10, piglet wrote:
On 05/05/2023 7:10 am, Anthony William Sloman wrote:

snip

I assume you can recommend some amazingly effective antidepressents.
May I know the name(s) of them? (Asking for a friend). :)

No. Personally, so far, getting exercize (hiking San Francisco!) and
keeping my weight down is working. Designing things keeps me happy
too. Is your friend deep depressed or bipolar?
Early \'days\' so far, but looks like Bipolar and possibly type 2. She\'s
not responding very well to the current regime (some combo of
Quetiapine and Pregabalin). I told her to go back to the dox and ask
about switching to Lithium, which as you will know was the go-to med
of first choice back in the day (and presumably is still available).

Your thoughts?

Lithium is very specific to bipolar. One of my cousins did his Ph.D. on it\'s use back when I was doing mine.

My only bipolar friend won\'t use it because he likes being manic - when it happens.
Click to expand...

Yes, but it can be highly dangerous (full-blown mania as opposed to
hypomania - unless you meant the latter). Mania generally requires
hospitalisation for the safety of the patient. I believe that\'s one of
the key distinctions between type 1 and 2. IIRC I think type 1 is the
one where they get full blown mania whereas type 2 never gets beyond
hypomania. Fascinating subject. Funny thing is, she was one of the
most stable people I\'ve ever known until she got this, from of all
things, a UTI at the age of 56. Who\'d have thought a simple bacterial
infection could have such long lasting and severe complications with
mental health?
 
On Mon, 08 May 2023 05:35:04 -0700, John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote:

On Mon, 08 May 2023 13:04:10 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Mon, 08 May 2023 04:43:24 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Mon, 08 May 2023 00:23:58 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Sun, 7 May 2023 22:38:18 +0100, piglet <erichpwagner@hotmail.com
wrote:

On 07/05/2023 13:39, Cursitor Doom wrote:

Well, I\'ve never seen anything like this before in a linear PSU from a
respected company. It\'s almost as if they were forced to use
transformers with not enough suitable secondary windings. There\'s a
revision date on this board: 1971.

Not sure I understand why you think there aren\'t enough secondary
windings? There is one for -/+50, one for -/+15 one for +5 and one for
80-90 which added to +50 made 130V. Seems like plenty, how would more
windings make it simpler? The 130V regulation occurring at 50V is
economical, other HV supplies of that era used that trick too.

piglet

Well it\'s simple for you because you\'re an electronics wizzard, Erich.
I\'m just a humble hobbyist and \"not particularly good at electronics\"
as I describe myself. I certainly did the right thing by not taking it
up as a career, I\'m perfectly certain of that.

Well, that Tek schamatic is kind of a tangle. Not at all obvious on
first sight.

I\'ve been chatting to some chap on another forum who\'s repaired
several of these boards and he agrees. They\'re a pain in the arse
having those interdependencies and I don\'t care what the venerable
piglet says to the contrary.


Maybe you\'re not autistic enough to be very good at electronics
design.

I just find it fascinating how different people excell at certain
things, but are useless at others. It\'s a source of infinite wonder to
me.

Humans sure specialize. I think that, in a tribe, some people grow
food, some make arrows, and some shoot arrows. Cows and oysters don\'t
seem to specialize as much.

What fascinates me is how humans, hunter-gatherers, evolved to be able
to do calculus and design electronics.
Click to expand...

Simply by standing on the shoulders of giants. We\'re talking mostly
small discoveries and inventions over huge periods of time, with the
odd quantum leap thrown in every couple of hundred years. Now we stand
on the brink of AI and that should be the new quantum leap.
 
On Mon, 8 May 2023 13:35:54 +0100, piglet <erichpwagner@hotmail.com>
wrote:

On 08/05/2023 13:04, Cursitor Doom wrote:
I\'ve been chatting to some chap on another forum who\'s repaired
several of these boards and he agrees. They\'re a pain in the arse
having those interdependencies and I don\'t care what the venerable
piglet says to the contrary.


Haha, thanks for the accolade!

Yes, there are interactions. At a guess I\'d suggest first making
something come out the +130V pin, doesn\'t need to 130 yet, even 60-80V
would do. Then work on getting the -50V section working, all the rest
are keyed to that. Next the +50V regulator, then recheck the 130V is now
right. Then -15V, then +15, lastly +5V and then go back and recheck all.
Then reconnect to rest of the scope and see what happens.

the venerable piglet
Click to expand...

Thanks for that, VP. Just what I needed: a starting point and an order
of testing to follow. Ausgezeichnet!
 
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