Brownface Potentiometers

[strat100]

It's obvious that the signal is getting mixed into both channels but finding it is being a problem for me, think that the problem is I am finding it hard to know exactly where the signal should be and where it shouldn't as I can't decipher the schematic of the vibrato part, any one up for drawing the signal trace through the vibrato part to help me?

[martin manning]

Is the power amp working? You might try disconnecting the negative feedback, and/or lifting the end of the PI input cap (at the red arrow, which isolates the power amp from the preamp) and feeding signal in there.

[sluckey]

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[sluckey]

Hey Martin, what is the name of the font you used in your marked up schematic? I like it.

EDIT... Never mind. I found the Bradley Hand font pretty quickly but it was just too thin in Visio. Using bold did not help. Then it finally dawned on me that you probably used a graphics program to insert the text. As soon as I inserted text through PSP I was able to change the stroke width and match your text exactly.

[martin manning]

Yes Bradley Hand is correct. I'm not as sophisticated as you are. I do all of my sketching in PowerPoint :^)

[sluckey]

Haha. Sophistication is relative and highly overrated.

[M Fowler]

The last time I needed that 10M RA pot I got it from TAD but now they don't list it.

Mark

[strat100]

Thank you Gentlemen that is perfect will have a look and see what i can find later.
The power amp is working but the signal is louder on i side of the P.I

[strat100]

Normal channel add audio and channel clean upto 220k mix resistor and o.oo1uf cap goes to pin 2 on v6 still clean this is where it goes pearshaped for me because on pins 1+3+6+7+8 its got the vibrato. Confused.com

[sluckey]

Normal channel add audio and channel clean upto 220k mix resistor and o.oo1uf cap goes to pin 2 on v6 still clean this is where it goes pearshaped for me because on pins 1+3+6+7+8 its got the vibrato. Confused.com

Just pull V2, V3, V4, and V5. This totally removes the VIB channel leaving just a simple one channel amp. Now get the normal channel working properly before putting those tubes back in.

[strat100]

Just done that and its distorted ring modulated so going to lift the 0.05 cap and feed it direct to power amp

[strat100]

So its in the power amp somewhere as lifted the 0.05uf cap and attached to the 0.001uf cap and sound still distorted, going to try lifting the feedback loop now.

[strat100]

Lifted feedback loop and no change.Any ideas what i try next?

[strat100]

Chased signal through power amp and its clean till it hits pin 3 on both power tubes

[sluckey]

Chased signal through power amp and its clean till it hits pin 3 on both power tubes

Probably not a good idea to connect a scope to pin 3 of the output tubes. Safer to connect to the speaker jack.

With no signal applied measure the voltages on pins 3, 4, 5, and 8 of both power tubes. What have you?