Toshiba TV29C90 problem; Image fades to black...

[Smitty Two]

In article <4f9e3bfe9bdave@davenoise.co.uk>,
"Dave Plowman (News)" <dave@davenoise.co.uk> wrote:

In article <dIqdnb7olaJ_Y7rVnZ2dnUVZ_rzinZ2d@comcast.com>,
Michael Kennedy <Mikek400@remthis.comcast.net> wrote:
What becomes obsolete in a power supply?

Good question.. Maybe he is talking about a ATX PC power supply? All of
my AT power supplies are unfortunately obsolete, at least for use in
modern computers.

Indeed - but the OP talked about a 30v 10A CVCC PS. Not that I know what
CVCC is - Google suggests it's the Cuckmere Valley Canoe Club. Perhaps
they use some form of electrolysis to reduce friction? ;-)

Constant Voltage Constant Current. AIUI, the OP isn't talking about a
computer power supply, or a benchtop piece of test equipment, but
something to build into a chassis of a custom piece of gear. We stick
with Lambda or Power One and have good results.

 

[Smitty Two]

In article <68r0qaF2ur81qU1@mid.individual.net>,
Adrian C <email@here.invalid> wrote:

Smitty Two wrote:
In article <4f9e3bfe9bdave@davenoise.co.uk>,
"Dave Plowman (News)" <dave@davenoise.co.uk> wrote:

In article <dIqdnb7olaJ_Y7rVnZ2dnUVZ_rzinZ2d@comcast.com>,
Michael Kennedy <Mikek400@remthis.comcast.net> wrote:
What becomes obsolete in a power supply?
Good question.. Maybe he is talking about a ATX PC power supply? All of
my AT power supplies are unfortunately obsolete, at least for use in
modern computers.
Indeed - but the OP talked about a 30v 10A CVCC PS. Not that I know what
CVCC is - Google suggests it's the Cuckmere Valley Canoe Club. Perhaps
they use some form of electrolysis to reduce friction? ;-)

Constant Voltage Constant Current. AIUI, the OP isn't talking about a
computer power supply, or a benchtop piece of test equipment, but
something to build into a chassis of a custom piece of gear. We stick
with Lambda or Power One and have good results.

Correct regarding CV/CC but the OP is more than likely talking about a
variable bench supply He is also asking for help how to use it, and
may be looking for what the difference between voltage and current and
what an adjustable current limit (damm useful!), sense connectors and
ground lift/connect may be used for.

Such things will be glossed over in the average chinese manual as those
concepts are self explanatory for the engineer person specifying and
buying such a unit. HP's (and most US written) manuals may be a bit more
forthcoming?

His is probably like Mastech's <http://multimetercenter.com/hy3010Df.htm

Anyway, My experience is with Thurlby (TTi) bench power supplies, don't
know if these made it much in the US direction - but popular here in the
UK for business and education use.

We need the OP back ...

He stumbled in here from Google (so I'm among many who only saw replies)
and probably can't find his way back.

 

[Smitty Two]

In article <68r0qaF2ur81qU1@mid.individual.net>,
Adrian C <email@here.invalid> wrote:

Smitty Two wrote:
In article <4f9e3bfe9bdave@davenoise.co.uk>,
"Dave Plowman (News)" <dave@davenoise.co.uk> wrote:

In article <dIqdnb7olaJ_Y7rVnZ2dnUVZ_rzinZ2d@comcast.com>,
Michael Kennedy <Mikek400@remthis.comcast.net> wrote:
What becomes obsolete in a power supply?
Good question.. Maybe he is talking about a ATX PC power supply? All of
my AT power supplies are unfortunately obsolete, at least for use in
modern computers.
Indeed - but the OP talked about a 30v 10A CVCC PS. Not that I know what
CVCC is - Google suggests it's the Cuckmere Valley Canoe Club. Perhaps
they use some form of electrolysis to reduce friction? ;-)

Constant Voltage Constant Current. AIUI, the OP isn't talking about a
computer power supply, or a benchtop piece of test equipment, but
something to build into a chassis of a custom piece of gear. We stick
with Lambda or Power One and have good results.

Correct regarding CV/CC but the OP is more than likely talking about a
variable bench supply He is also asking for help how to use it, and
may be looking for what the difference between voltage and current and
what an adjustable current limit (damm useful!), sense connectors and
ground lift/connect may be used for.

Such things will be glossed over in the average chinese manual as those
concepts are self explanatory for the engineer person specifying and
buying such a unit. HP's (and most US written) manuals may be a bit more
forthcoming?

His is probably like Mastech's <http://multimetercenter.com/hy3010Df.htm

Anyway, My experience is with Thurlby (TTi) bench power supplies, don't
know if these made it much in the US direction - but popular here in the
UK for business and education use.

We need the OP back ...

He stumbled in here from Google (so I'm among many who only saw replies)
and probably can't find his way back.

 

[Dave Plowman (News)]

In article <68r0qaF2ur81qU1@mid.individual.net>,
Adrian C <email@here.invalid> wrote:

Constant Voltage Constant Current. AIUI, the OP isn't talking about a
computer power supply, or a benchtop piece of test equipment, but
something to build into a chassis of a custom piece of gear. We stick
with Lambda or Power One and have good results.

Correct regarding CV/CC but the OP is more than likely talking about a
variable bench supply

Just curious what use a constant current constant voltage bench supply
would be? Or does it mean *either* constant voltage or constant current?

--
*If you try to fail, and succeed, which have you done?

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[Dave Plowman (News)]

In article <68r0qaF2ur81qU1@mid.individual.net>,
Adrian C <email@here.invalid> wrote:

Constant Voltage Constant Current. AIUI, the OP isn't talking about a
computer power supply, or a benchtop piece of test equipment, but
something to build into a chassis of a custom piece of gear. We stick
with Lambda or Power One and have good results.

Correct regarding CV/CC but the OP is more than likely talking about a
variable bench supply

Just curious what use a constant current constant voltage bench supply
would be? Or does it mean *either* constant voltage or constant current?

--
*If you try to fail, and succeed, which have you done?

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[Michael Moroney]

"daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> writes:

P.S. In the US, a 'tap-changer' may be built for either for unloaded or
loaded operation. The 'unloaded' type can not be stepped to another tap
while there is load on the unit (although it can still be energized). It's
switch contacts cannot interrupt load though, so if you try to move it while
loaded, you can burn up the tap-changer. The classic 'load-tap-changer' is
actually several switches that are controlled in a precise sequence to shift
the load from one tap of the transformer to another while not interrupting
the load current.

P.P.S. Load tap changers typically have a significant time-delay built into
the controls so they do not 'hunt' or respond to short drops in voltage such
as starting a large load. 15 seconds to several minutes is typical. So
even with load-tap-changers, starting a single load that is a high
percentage of the system capacity will *still* result in a voltage dip.

Are the load tap generators configured make-before-break?
Break-before-make would mean a (very short) power outage every activation
but make-before-break would mean a momentarily short-circuited winding and
the break would involve interrupting a large short circuit current.

Certainly modern ones likely use thyristors and zero crossing detectors.

When I was a kid living in a rather rural area, there would be a pair of
these on poles every few miles, connected open delta. (all transformer
primaries were connected phase-phase then).

 

[Michael Moroney]

"daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> writes:

P.S. In the US, a 'tap-changer' may be built for either for unloaded or
loaded operation. The 'unloaded' type can not be stepped to another tap
while there is load on the unit (although it can still be energized). It's
switch contacts cannot interrupt load though, so if you try to move it while
loaded, you can burn up the tap-changer. The classic 'load-tap-changer' is
actually several switches that are controlled in a precise sequence to shift
the load from one tap of the transformer to another while not interrupting
the load current.

P.P.S. Load tap changers typically have a significant time-delay built into
the controls so they do not 'hunt' or respond to short drops in voltage such
as starting a large load. 15 seconds to several minutes is typical. So
even with load-tap-changers, starting a single load that is a high
percentage of the system capacity will *still* result in a voltage dip.

Are the load tap generators configured make-before-break?
Break-before-make would mean a (very short) power outage every activation
but make-before-break would mean a momentarily short-circuited winding and
the break would involve interrupting a large short circuit current.

Certainly modern ones likely use thyristors and zero crossing detectors.

When I was a kid living in a rather rural area, there would be a pair of
these on poles every few miles, connected open delta. (all transformer
primaries were connected phase-phase then).

 

[propman]

Bill <billp@rhondasworld.com> wrote in
newsan.2008.05.12.18.24.56.893717@rhondasworld.com:

I have an RCA g35302wk that has been a great TV for a number of years.
Recently it started doing this funky thing where the picture would
collapse and you are left with a thin horizontal line all the way
across the screen.

AKA "vertical collapse"

The line is very bright, and the television still
has audio when this happens. At first if you turned the TV off for a
few minutes then back on the picture would clear up and it would be ok
for a random amount of time, between about 1/2 hour and 2 hours.

Possible indication of a thermal problem.

morning though it went into the collapsed state and has been stuck
there ever since. I found very little repair infor for this TV on the
internet, one page said to replace U3101 (210736), U3200 (209956) and
microprocessor. But I dont think that is causing this issue. Can
anyone give me any tips on anything else that may be causing this
picture collapse? I did replace the power supply about 2 years ago. I
am skilled in electronics and do have experience with HV systems, I
just do not know where to being looking. I know the NEW HD world is
coming up, but I would love to keep this TV going if it can be fixed
without much trouble.

Certainly no expert here but I just fixed my RCA Home Theater (model
#F31224GG made in 1993) with exactly the same problem you are
experiencing. Turns out it was a bad solder joint for a resistor in the
vertical section; one leg of the resistor had come completely free from
the board's solder pad.

As the previous poster mentioned, try tapping the circuit board with an
insulated none-metallic implement of destruction (grin).....in my case,
the video began jumping more the closer I got to the defective joint.
Also try moving the legs of the various components where they attach to
their pads....usually the bad leg connection will move freely with
little effort.

If after trying this method nothing is readily apparent, then you might
have a cracked circuit board trace.....use previously mentioned
implement of destruction to put pressure on the board itself to see if
the trace will join itself back together. Giving the board an eyeball
over with a magnifying glass is another method to try.

If none of the above works out, then it's time to start looking for
failed components with various pieces of testing equipment and
troubleshooting methods.....which for the most part I will leave up to
more knowledgable participants in this newsgroup to share their wisdom
with you.

Good luck.....hopefully you will be able to track down the source of the
problem.

 

In alt.engineering.electrical Tzortzakakis Dimitrios <noone@nospam.void> wrote:

| A shame that Tesla won the infamous "battle" and we don't have DC:-() But
| then, we would be having a power plant at each neighborhood, instead of the
| 300 MW ones.

And the latter make easy terrorism targets, too.


| I know, I know, my answer was a bit provocative And of course there are
| DC regulators.... You're talking about DC generators;the one a 300 MW uses
| for excitation is 220 V, 1000 A DC and probably shunt field. I have seen
| here in some machine shops the old type welding generator, which is a 3
| phase induction motor coupled to (usually) a compound field DC generator,
| which provides the welding current. The modern ones are, maybe, not larger
| than a shoe box and powered by a higher wattage 230 V 16 A receptacle.
| (Usual receptacles are 230 V 10 A;16 A for washing machines, dryers and the
| like).

You don't use 400 V for anything heavy duty like an oven?

--
|WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance |
| by the abuse department, bellsouth.net is blocked. If you post to |
| Usenet from these places, find another Usenet provider ASAP. |
| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |

 

In alt.engineering.electrical Tzortzakakis Dimitrios <noone@nospam.void> wrote:

| A shame that Tesla won the infamous "battle" and we don't have DC:-() But
| then, we would be having a power plant at each neighborhood, instead of the
| 300 MW ones.

And the latter make easy terrorism targets, too.


| I know, I know, my answer was a bit provocative And of course there are
| DC regulators.... You're talking about DC generators;the one a 300 MW uses
| for excitation is 220 V, 1000 A DC and probably shunt field. I have seen
| here in some machine shops the old type welding generator, which is a 3
| phase induction motor coupled to (usually) a compound field DC generator,
| which provides the welding current. The modern ones are, maybe, not larger
| than a shoe box and powered by a higher wattage 230 V 16 A receptacle.
| (Usual receptacles are 230 V 10 A;16 A for washing machines, dryers and the
| like).

You don't use 400 V for anything heavy duty like an oven?

--
|WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance |
| by the abuse department, bellsouth.net is blocked. If you post to |
| Usenet from these places, find another Usenet provider ASAP. |
| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |

 

In alt.engineering.electrical Michael Moroney <moroney@world.std.spaamtrap.com> wrote:

| Are the load tap generators configured make-before-break?
| Break-before-make would mean a (very short) power outage every activation
| but make-before-break would mean a momentarily short-circuited winding and
| the break would involve interrupting a large short circuit current.

I wonder how much regulation could be managed through the use of variable
leakage inductance in the transformer windings.


| Certainly modern ones likely use thyristors and zero crossing detectors.

With zero crossing detection, then the switching is not happening on all phases
at the same time.

--
|WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance |
| by the abuse department, bellsouth.net is blocked. If you post to |
| Usenet from these places, find another Usenet provider ASAP. |
| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |

 

In alt.engineering.electrical Michael Moroney <moroney@world.std.spaamtrap.com> wrote:

| Are the load tap generators configured make-before-break?
| Break-before-make would mean a (very short) power outage every activation
| but make-before-break would mean a momentarily short-circuited winding and
| the break would involve interrupting a large short circuit current.

I wonder how much regulation could be managed through the use of variable
leakage inductance in the transformer windings.


| Certainly modern ones likely use thyristors and zero crossing detectors.

With zero crossing detection, then the switching is not happening on all phases
at the same time.

--
|WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance |
| by the abuse department, bellsouth.net is blocked. If you post to |
| Usenet from these places, find another Usenet provider ASAP. |
| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |

 

[danny burstein]

In <g0a7lq0t0c@news5.newsguy.com> phil-news-nospam@ipal.net writes:

In alt.engineering.electrical Tzortzakakis Dimitrios <noone@nospam.void> wrote:

| A shame that Tesla won the infamous "battle" and we don't have DC:-() But
| then, we would be having a power plant at each neighborhood, instead of the
| 300 MW ones.

And the latter make easy terrorism targets, too.

And so does that 20 gallons of gasoline parked
in front of your house. And that 500 gallons
of diesel fuel in your basment. And that 20,000
or so gallons in the nearby gas station.

Yawn.

--
_____________________________________________________
Knowledge may be power, but communications is the key
dannyb@panix.com
[to foil spammers, my address has been double rot-13 encoded]

 

[danny burstein]

In <g0a7lq0t0c@news5.newsguy.com> phil-news-nospam@ipal.net writes:

In alt.engineering.electrical Tzortzakakis Dimitrios <noone@nospam.void> wrote:

| A shame that Tesla won the infamous "battle" and we don't have DC:-() But
| then, we would be having a power plant at each neighborhood, instead of the
| 300 MW ones.

And the latter make easy terrorism targets, too.

And so does that 20 gallons of gasoline parked
in front of your house. And that 500 gallons
of diesel fuel in your basment. And that 20,000
or so gallons in the nearby gas station.

Yawn.

--
_____________________________________________________
Knowledge may be power, but communications is the key
dannyb@panix.com
[to foil spammers, my address has been double rot-13 encoded]

 

[Michael Moroney]

phil-news-nospam@ipal.net writes:

In alt.engineering.electrical Michael Moroney <moroney@world.std.spaamtrap.com> wrote:

| Are the load tap generators configured make-before-break?
| Break-before-make would mean a (very short) power outage every activation
| but make-before-break would mean a momentarily short-circuited winding and
| the break would involve interrupting a large short circuit current.

I wonder how much regulation could be managed through the use of variable
leakage inductance in the transformer windings.

Good question.

| Certainly modern ones likely use thyristors and zero crossing detectors.

With zero crossing detection, then the switching is not happening on all phases
at the same time.

Since the ones I've seen are 3 (or 2) independent autotransformers, this
is true without zero crossing detectors, and the power supplied may not
always be of equal voltages 120 degrees apart.

 

[Michael Moroney]

phil-news-nospam@ipal.net writes:

In alt.engineering.electrical Michael Moroney <moroney@world.std.spaamtrap.com> wrote:

| Are the load tap generators configured make-before-break?
| Break-before-make would mean a (very short) power outage every activation
| but make-before-break would mean a momentarily short-circuited winding and
| the break would involve interrupting a large short circuit current.

I wonder how much regulation could be managed through the use of variable
leakage inductance in the transformer windings.

Good question.

| Certainly modern ones likely use thyristors and zero crossing detectors.

With zero crossing detection, then the switching is not happening on all phases
at the same time.

Since the ones I've seen are 3 (or 2) independent autotransformers, this
is true without zero crossing detectors, and the power supplied may not
always be of equal voltages 120 degrees apart.

 

[Ol' Duffer]

In article <5apg241m4gkpcuhsje4gbbiqabp6q9u0j2@4ax.com>,
markrrivet@verizon.net says...

What are the benefits of using a permanent magnet for a coil core.
I recently came across a design for a switching power supply that used
magnets as cores for the inductor. I have never heard of such a thing,
except maybe in speakers.

If there is DC current flowing in the coil, it reduces the amount of
flux "swing" that can happen without saturating the core. Or looking
at it from another angle, you need a physically larger (more $$) core
to do the same AC work if it is also carrying DC. Using a permanent
magnet to counteract the DC flux allows a smaller (cheaper) part to
be used. Used to see these in the vertical section of TV's in the
days before power IC's.

 

[Mark D. Zacharias]

<tx7123@yahoo.com> wrote in message
news:ec371b58-59da-4066-97bb-e9013a2231d4@e53g2000hsa.googlegroups.com...
On May 11, 10:13 pm, "Mark D. Zacharias" <mzachar...@nonsense.net>
wrote:

tx7...@yahoo.com> wrote in message

news:89bc8f04-d26f-4237-8b8a-3f1495b191b6@f63g2000hsf.googlegroups.com...
On May 11, 9:07 am, "Mark D. Zacharias" <mzachar...@nonsense.net
wrote:





tx7...@yahoo.com> wrote in message

news:b2fdab22-8f8c-4c93-a720-d79cc0fe3bff@i76g2000hsf.googlegroups.com...
On May 3, 5:19 pm, "Mark D. Zacharias" <mzachar...@nonsense.net
wrote:

Hi ,

SNIP

I decided to lift the board and look at the solder for the device

sanyo 313e.
Before I could do anything the V shaped metal (heatsink?) attached >to
the
device just fell off. The plastic screw holding it had just cracked >in
half.
There also is a thin piece of plastic between the device and the
heatsink.
I'm assuming that they do want the device to touch the metal.
I could not find a another plastic screw, so I use a metal one with
an
insulating washer. I hope that is ok. Why does the device need to >be
insulated from the metal heatsink. Is it strictly pecautionary, in
case
the heatsink comes in contact with something else. Would it be ok
to put some cpu grease between the device and the plastic >insulator?
Anyway after all this the solder looked ok, so I did not resolder.
I wonder if my problem all along was that the heatsink
was just hanging on by a thread.

Anyway it seems to work ok. I'll run it for a while with the case>open

as a precaution.

Thanks

If the solder is really OK, which I doubt. Then the transistor is
failing.
On this TO-220 case transistor this most commonly happens from a
base-emitter junction opening up internally.

If you were to look very closely at the solder connections ( I recommend
a
magnifying glass) I believe you will see the ring-cracks around the
transistor leads.

In this particular case the heat sink has no other electrical
connection,
but you are still going to need another screw and nut. Another mica
insulator and some silicon grease would be good, although as I say, in
this
case I think you could dispense with the mica.

Alternatively you could use a newer style TO-220PL plastic case
transistor
such as a 2SC4793 which requires no insulator.

It's unfortunate in a way that your skills and experience don't seem to
quite be up to the task. I don't say that as a put-down, but this whole
thing should have been over long ago.

If you decide to replace the transistor, you'll need a source for the
part,
and most suppliers have 15.00 to 20.00 minimum orders.

You might consider OEQuotefix to fix your problem with Outlook Express
making messy looking posts. It's a free download.

Mark Z.- Hide quoted text -

- Show quoted text -

No need to be nasty.
The solder looked ok to me.
The board is very old, so the plan is to proceed cautiously.
I have attached the device properly to the heatsink.
If the problem recurrs, I will reheat the solder joints.
If that does not solve the problem then I will replace the device.
I'm assuming that a 2sd613 will be an adequate replacement, correct?

*****************************
A 2SD 613 would be fine.

I'm not sure why the > marks aren't showing in the quoted sections, I had
to
add them manually last time.

I don't feel I was being nasty before, even said so:

I don't say that as a put-down, but this whole
thing should have been over long ago.

I was watching as several other responders were telling you to replace the
transistor and a lot of back-and-forth when as I say this coulda / shoulda
been over with long ago.

mz- Hide quoted text -

- Show quoted text -

OK thanks sounds good.
One more question.
In the process of lifting the board to examine underneath,
the plastic tabs that hold the board in place are very brittle.
One broke and the others half broke off. Can I pull these out
from the side that the power supply board is on?
I'm thinking that mayb I can replace these with some
computer mainboard ones that I have lying around?

Thanks

Yes, if the area to be soldered can only be accessed by pulling the board
up - it's been a long time since I've worked on a 727. I was thinking the
board could be accessed from underneath.


Mark Z.

 

[Mark D. Zacharias]

<tx7123@yahoo.com> wrote in message
news:ec371b58-59da-4066-97bb-e9013a2231d4@e53g2000hsa.googlegroups.com...
On May 11, 10:13 pm, "Mark D. Zacharias" <mzachar...@nonsense.net>
wrote:

tx7...@yahoo.com> wrote in message

news:89bc8f04-d26f-4237-8b8a-3f1495b191b6@f63g2000hsf.googlegroups.com...
On May 11, 9:07 am, "Mark D. Zacharias" <mzachar...@nonsense.net
wrote:





tx7...@yahoo.com> wrote in message

news:b2fdab22-8f8c-4c93-a720-d79cc0fe3bff@i76g2000hsf.googlegroups.com...
On May 3, 5:19 pm, "Mark D. Zacharias" <mzachar...@nonsense.net
wrote:

Hi ,

SNIP

I decided to lift the board and look at the solder for the device

sanyo 313e.
Before I could do anything the V shaped metal (heatsink?) attached >to
the
device just fell off. The plastic screw holding it had just cracked >in
half.
There also is a thin piece of plastic between the device and the
heatsink.
I'm assuming that they do want the device to touch the metal.
I could not find a another plastic screw, so I use a metal one with
an
insulating washer. I hope that is ok. Why does the device need to >be
insulated from the metal heatsink. Is it strictly pecautionary, in
case
the heatsink comes in contact with something else. Would it be ok
to put some cpu grease between the device and the plastic >insulator?
Anyway after all this the solder looked ok, so I did not resolder.
I wonder if my problem all along was that the heatsink
was just hanging on by a thread.

Anyway it seems to work ok. I'll run it for a while with the case>open

as a precaution.

Thanks

If the solder is really OK, which I doubt. Then the transistor is
failing.
On this TO-220 case transistor this most commonly happens from a
base-emitter junction opening up internally.

If you were to look very closely at the solder connections ( I recommend
a
magnifying glass) I believe you will see the ring-cracks around the
transistor leads.

In this particular case the heat sink has no other electrical
connection,
but you are still going to need another screw and nut. Another mica
insulator and some silicon grease would be good, although as I say, in
this
case I think you could dispense with the mica.

Alternatively you could use a newer style TO-220PL plastic case
transistor
such as a 2SC4793 which requires no insulator.

It's unfortunate in a way that your skills and experience don't seem to
quite be up to the task. I don't say that as a put-down, but this whole
thing should have been over long ago.

If you decide to replace the transistor, you'll need a source for the
part,
and most suppliers have 15.00 to 20.00 minimum orders.

You might consider OEQuotefix to fix your problem with Outlook Express
making messy looking posts. It's a free download.

Mark Z.- Hide quoted text -

- Show quoted text -

No need to be nasty.
The solder looked ok to me.
The board is very old, so the plan is to proceed cautiously.
I have attached the device properly to the heatsink.
If the problem recurrs, I will reheat the solder joints.
If that does not solve the problem then I will replace the device.
I'm assuming that a 2sd613 will be an adequate replacement, correct?

*****************************
A 2SD 613 would be fine.

I'm not sure why the > marks aren't showing in the quoted sections, I had
to
add them manually last time.

I don't feel I was being nasty before, even said so:

I don't say that as a put-down, but this whole
thing should have been over long ago.

I was watching as several other responders were telling you to replace the
transistor and a lot of back-and-forth when as I say this coulda / shoulda
been over with long ago.

mz- Hide quoted text -

- Show quoted text -

OK thanks sounds good.
One more question.
In the process of lifting the board to examine underneath,
the plastic tabs that hold the board in place are very brittle.
One broke and the others half broke off. Can I pull these out
from the side that the power supply board is on?
I'm thinking that mayb I can replace these with some
computer mainboard ones that I have lying around?

Thanks

Yes, if the area to be soldered can only be accessed by pulling the board
up - it's been a long time since I've worked on a 727. I was thinking the
board could be accessed from underneath.


Mark Z.

 

In sci.electronics.repair jakdedert <jakdedert@bellsouth.net> wrote:

I'm a little confused about a 230 volt circuit. In what part of the
world does the utility supply 230v?

Continental Europe used to have 220 volts (before that it was 127 volts in
some places), the UK used to have 240 volts. Nowadays, the common voltage
is 230 volts -10% +6%.

--
Met vriendelijke groet,

Maarten Bakker.