UA 1176 info

[ilfungo]

Hi
I'm working on real 1176 layout and I'm near to finish it.
On new UA 1176 there is a cap not present in old unit
Can someone help to identify it?
Seems between Emitter of Q4 and junction R33 - C15 ???
Thanks

 

[RuudNL]

Can you read the value? It might be a cap to 'tame' the HF response. (To avoid oscillation.)

 

[ilfungo]

No I can't read the value...
which could be a good value?
Thanks!

 

[abbey road d enfer]

Seems between Emitter of Q4 and junction R33 - C15 ???

Are you sure? Which Revision is it? All revisions from A to K have Q4 as the last transistor in the "signal preamp" (gain reduction stage), and R33/C15 in the "signal line amp" (output stage), and there is no junction between C15 and R33...

 

[ilfungo]

I think could be a REV D-E
In the schematics R33 and C15 are connected .
This cap is connected from one side between them and the other side to Emitter of Q4, you can see on the images the traces.
The same cap si also in 1176 AE Version.
Thanks

 

[abbey road d enfer]

I think could be a REV D-E
In the schematics R33 and C15 are connected .

Correct.
But I don't see a schemo where R33 are connected.
Why can't you read the value?
In all likelihood, it is there to linearize the frequency response, so there is no "good" value. It is meant to compensate imperfections in the transformer, so it's impossible to determine a suitable value, because we don't know these imperfections.

 

[ilfungo]

Hi
R33 is connected to BRN (transformer primary) and R29 (1.2M).
below REV E schematic with cap ( unknown) connections
I can't read the value because I don't have a real unit but just this image...
someone have the real unit and can help me?
Thanks!

 

[abbey road d enfer]

Hi
R33 is connected to BRN (transformer primary) and R29 (1.2M).
below REV E schematic with cap ( unknown) connections
I can't read the value because I don't have a real unit but just this image...
someone have the real unit and can help me?
Thanks!

The drawing's definition is so good I read R35/C16!
OK, so it looks like this capacitor may be across R20(?), of 27k (?). So that would be there to tame the HF response, and as I wrote earlier, there is no way we can calculate it.

 

[ilfungo]

Ok Thanks!
If someone have the real unit and can help....
The cap is mica cap above C12
Thanks!

 

[ilfungo]

nobody?
Thanks!

 

[ilfungo]

Problem solved!
100pf
I've just received the info from a member of Gearsluz forum!
Thanks!