Amplifer Design

C

Cursitor Doom

Guest
Greetings, gentlemen,

This is the schematic of the CRO x-amplifier I've been investigating
lately. It's supposed to provide sufficient potential difference to the x
plates in the tube so as to sweep the electron beam left to right in
accordance with the timebase setting:

https://yandex.com/collections/card/5da36a58f05bf23ffde0742e/

At first I thought this was operating as some kind of complimentary pair
chain of stages, but it's only quasi-complimentary and I can't fully
understand how it works. The signal path is shown in slightly heavier
lines. It starts off conventionally enough, with a sawtooth sweep
waveform of approx half a volt applied to the base of Q10, but then why
does it then passed to the *emitter* of Q15? This is the part I'm
struggling to understand most.

What is the name for this type of configuration and why is the input
signal to Q15 being applied to its emitter rather than its base?
Thanks.


(if it were *truly* complimentary/push-pull then I'd have thought there
should be a *minus* 158V supply for the final stage of the lower chain,
but it states +158V which makes no sense to me).



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Tom Gardner wrote...
On 13/10/19 19:40, Cursitor Doom wrote:
Greetings, gentlemen,

This is the schematic of the CRO x-amplifier I've been investigating
lately. It's supposed to provide sufficient potential difference to the x
plates in the tube so as to sweep the electron beam left to right in
accordance with the timebase setting:

https://yandex.com/collections/card/5da36a58f05bf23ffde0742e/

Why do you post that on a Russian company's servers,
rather than dropbox?

Aren't you allowed to use/access dropbox or another
western company's servers?
Click to expand...

Also, is your name Paul B. ?


--
Thanks,
- Win
 
On 13/10/19 19:40, Cursitor Doom wrote:
Greetings, gentlemen,

This is the schematic of the CRO x-amplifier I've been investigating
lately. It's supposed to provide sufficient potential difference to the x
plates in the tube so as to sweep the electron beam left to right in
accordance with the timebase setting:

https://yandex.com/collections/card/5da36a58f05bf23ffde0742e/
Click to expand...

Why do you post that on a Russian company's servers,
rather than dropbox?

Aren't you allowed to use/access dropbox or another
western company's servers?
 
On 13/10/2019 19:40, Cursitor Doom wrote:
Greetings, gentlemen,

This is the schematic of the CRO x-amplifier I've been investigating
lately. It's supposed to provide sufficient potential difference to the x
plates in the tube so as to sweep the electron beam left to right in
accordance with the timebase setting:

https://yandex.com/collections/card/5da36a58f05bf23ffde0742e/

At first I thought this was operating as some kind of complimentary pair
chain of stages, but it's only quasi-complimentary and I can't fully
understand how it works. The signal path is shown in slightly heavier
lines. It starts off conventionally enough, with a sawtooth sweep
waveform of approx half a volt applied to the base of Q10, but then why
does it then passed to the *emitter* of Q15? This is the part I'm
struggling to understand most.

What is the name for this type of configuration and why is the input
signal to Q15 being applied to its emitter rather than its base?
Thanks.


(if it were *truly* complimentary/push-pull then I'd have thought there
should be a *minus* 158V supply for the final stage of the lower chain,
but it states +158V which makes no sense to me).
Click to expand...

Q10 and Q15 are a diff-amp or long-tailed pair. Q11 is the tail current
source.

piglet
 
On Sun, 13 Oct 2019 13:17:04 -0700, jlarkin wrote:

> I couldn't see that at useful resolution.

I know; it's a PITA but there's nothing I can do as I pulled it off a
website myself. I've posted 2 versions, so you might see it better with
the enhanced one where I've tweaked things up a bit.



--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.
 
On Sun, 13 Oct 2019 13:21:14 -0700, Winfield Hill wrote:

> Hi Paul, nice to meet you!

Gleichfalls, Win. :)



--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.
 
Cursitor Doom wrote...
On Sun, 13 Oct 2019 12:35:25 -0700, Winfield Hill wrote:

Also, is your name Paul B. ?

Yup, as in Burridge.
Click to expand...

Hi Paul, nice to meet you!


--
Thanks,
- Win
 
On Sun, 13 Oct 2019 18:40:01 -0000 (UTC), Cursitor Doom
<curd@notformail.com> wrote:

Greetings, gentlemen,

This is the schematic of the CRO x-amplifier I've been investigating
lately. It's supposed to provide sufficient potential difference to the x
plates in the tube so as to sweep the electron beam left to right in
accordance with the timebase setting:

https://yandex.com/collections/card/5da36a58f05bf23ffde0742e/
Click to expand...

I couldn't see that at useful resolution.




--

John Larkin Highland Technology, Inc

lunatic fringe electronics
 
On Sun, 13 Oct 2019 20:08:02 +0100, Piglet wrote:

Q10 and Q15 are a diff-amp or long-tailed pair. Q11 is the tail current
source.
Click to expand...

Well I did suspect that initially, Erich, but the input signal is shown
only applied to the base of *one* of those transistors!




--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.
 
On Sun, 13 Oct 2019 12:35:25 -0700, Winfield Hill wrote:

Tom Gardner wrote...

On 13/10/19 19:40, Cursitor Doom wrote:
Greetings, gentlemen,

This is the schematic of the CRO x-amplifier I've been investigating
lately. It's supposed to provide sufficient potential difference to
the x plates in the tube so as to sweep the electron beam left to
right in accordance with the timebase setting:

https://yandex.com/collections/card/5da36a58f05bf23ffde0742e/

Why do you post that on a Russian company's servers,
rather than dropbox?

Aren't you allowed to use/access dropbox or another western company's
servers?

Also, is your name Paul B. ?
Click to expand...

Yup, as in Burridge.



--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.
 
Cursitor Doom wrote...
Greetings, gentlemen,

This is the schematic of the CRO x-amplifier I've been investigating
lately. It's supposed to provide sufficient potential difference to the x
plates in the tube so as to sweep the electron beam left to right in
accordance with the timebase setting:

https://yandex.com/collections/card/5da36a58f05bf23ffde0742e/
Click to expand...

What scope model did it come from?


--
Thanks,
- Win
 
Cursitor Doom <curd@notformail.com> wrote:
On Sun, 13 Oct 2019 13:17:04 -0700, jlarkin wrote:

I couldn't see that at useful resolution.

I know; it's a PITA but there's nothing I can do as I pulled it off a
website myself. I've posted 2 versions, so you might see it better with
the enhanced one where I've tweaked things up a bit.
Click to expand...

FWIW, <right mouse click> on the image and then choosing "View Image in
New Tab" from the popup menu, made the schematic readable for me. YMMV.

Thank you, 73,

--
Don Kuenz KB7RPU
There was a young lady named Bright Whose speed was far faster than light;
She set out one day In a relative way And returned on the previous night.
 
On Sun, 13 Oct 2019 14:03:39 -0700, Winfield Hill wrote:

> What scope model did it come from?

To be strictly accurate, it's actually an HP865A RF spectrum analyser.
Not that it makes any difference to the question in this instance. In
fact the y-amp uses *exactly* the same board as the x; something I'm
hoping will assist me in identifying the faulty component. So rarely does
something like that arise which can actually be invaluable in fault
tracing!



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This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
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GBP10.00 per reproduction. Publication in this manner via non-Usenet
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On Sun, 13 Oct 2019 16:25:52 -0700, Winfield Hill wrote:

> Can you recheck that HP model number?

Sorry, Win, it's actually 8565A.



--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.
 
Cursitor Doom wrote...
On Sun, 13 Oct 2019 14:03:39 -0700, Winfield Hill wrote:

What scope model did it come from?

To be strictly accurate, it's actually an HP865A RF spectrum analyser.
Click to expand...

Can you recheck that HP model number?


--
Thanks,
- Win
 
Cursitor Doom wrote:
Greetings, gentlemen,

This is the schematic of the CRO x-amplifier I've been investigating
lately. It's supposed to provide sufficient potential difference to the x
plates in the tube so as to sweep the electron beam left to right in
accordance with the timebase setting:

https://yandex.com/collections/card/5da36a58f05bf23ffde0742e/

At first I thought this was operating as some kind of complimentary pair
chain of stages, but it's only quasi-complimentary and I can't fully
understand how it works. The signal path is shown in slightly heavier
lines. It starts off conventionally enough, with a sawtooth sweep
waveform of approx half a volt applied to the base of Q10, but then why
does it then passed to the *emitter* of Q15? This is the part I'm
struggling to understand most.

What is the name for this type of configuration and why is the input
signal to Q15 being applied to its emitter rather than its base?
* Q10 / Q15 is a differential pair; Q11 is the current source.
Click to expand...

Thanks.


(if it were *truly* complimentary/push-pull then I'd have thought there
should be a *minus* 158V supply for the final stage of the lower chain,
but it states +158V which makes no sense to me).
Click to expand...
 
On 13.10.19 23:02, Cursitor Doom wrote:
On Sun, 13 Oct 2019 20:08:02 +0100, Piglet wrote:

Q10 and Q15 are a diff-amp or long-tailed pair. Q11 is the tail current
source.

Well I did suspect that initially, Erich, but the input signal is shown
only applied to the base of *one* of those transistors!
Click to expand...

That's how a diff pair is supposed to work, see e.g.
Win's excellent book.

--

-TV
 
On Mon, 14 Oct 2019 10:36:35 +0300, Tauno Voipio wrote:

That's how a diff pair is supposed to work, see e.g.
Win's excellent book.
Click to expand...

I shall! Thanks, all.



--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.
 
Tom Gardner wrote...
On 13/10/19 19:40, Cursitor Doom wrote:
Greetings, gentlemen,

This is the schematic of the CRO x-amplifier I've been investigating
lately. It's supposed to provide sufficient potential difference to the x
plates in the tube so as to sweep the electron beam left to right in
accordance with the timebase setting:

https://yandex.com/collections/card/5da36a58f05bf23ffde0742e/

Why do you post that on a Russian company's servers,
rather than dropbox?
Click to expand...

There's a 236MB file of the HP 8565A Operating and Service
Manual, dated 1977, 424 pages, on the web. Unfortunately,
it's locked, so I could not extract the pdf schematic page.
But I expanded it, and made an image of the HV output amp.

https://www.dropbox.com/s/o4tybr81cefbk5n/8565A_amp.GIF?dl=1

The 1st diff-amp stage has 562R emitter and 2k15 collector
resistors for G=3.8. The 2nd stage has 750 + 500-ohm trim
emitter resistors and a current output. The HV output stage
has a 19k6 feedback resistor, for G = 15 to 26, 19 nominal.
A 1pF feedback cap would set the video bandwidth at 8MHz.
I imagine Zout is less than 1k. Push-pull PNP & NPN BJTs,
running at 7mA, and dissipating 1 watt, go from 2V to 140V.
There are two complementary amps, for two deflection plates.



--
Thanks,
- Win
 
On Mon, 14 Oct 2019 05:59:23 -0700, Winfield Hill wrote:

There's a 236MB file of the HP 8565A Operating and Service Manual,
dated 1977, 424 pages, on the web. Unfortunately, it's locked, so I
could not extract the pdf schematic page. But I expanded it, and made
an image of the HV output amp.

https://www.dropbox.com/s/o4tybr81cefbk5n/8565A_amp.GIF?dl=1
Click to expand...

And a splendid image it is too. You're obviously way better than me at
enhancement.

The 1st diff-amp stage has 562R emitter and 2k15 collector resistors
for G=3.8. The 2nd stage has 750 + 500-ohm trim emitter resistors and
a current output. The HV output stage has a 19k6 feedback resistor,
for G = 15 to 26, 19 nominal. A 1pF feedback cap would set the video
bandwidth at 8MHz.
I imagine Zout is less than 1k. Push-pull PNP & NPN BJTs, running at
7mA, and dissipating 1 watt, go from 2V to 140V. There are two
complementary amps, for two deflection plates.
Click to expand...

It seems odd to me that there's no minus 158V supply for the final
voltage amp. It looks like they're relying solely on attracting the
electron beam from side to side with positive voltages swapping back and
forth between plates rather than a combination of attraction and
repulsion as I would have intuitively expected. :-/





--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.
 
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