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Old 2nd Dec 2021, 6:56 pm   #42
shaunpw
Triode
 
Join Date: Nov 2021
Location: Nottingham, Nottinghamshire, UK.
Posts: 17
Default Re: Quad 34 preamp volume knob clicks

ok, here we are with todays update.

I have now replaced IC1 & 2 (cd4066), IC24, 25, 26, 27 (all now OPA2134)
All the tests carried out with an input short plug.

I got myself a better DVM, now reading proper millivolts.

So, with radio selected, no resistors shorted, I get -41.1mv/-37.mv on IC27 op.
as above with cd selected, I get -4.5mv/-3.7mv on IC27 op.

Applying a short across R30, R29, R13 all give the same results, -0.5mv/-0.1mv on IC27 op.

I did find the track between pins 6,7 of IC27 and C30 was bringing a bit of stray voltage to the party so I removed the through pins and hard wired the connection with a section of screened cable, that helped stabilise all the testing.

The volume clicks are still present although it only happens once per input selection, if left on radio or cd, no more clicks after the first volume increment.

I've also checked the values of all the resistors on the input side and they are all within tolerance.

Thats as far as I have got.

Thanks for reading !
Shaun.
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