Telefunken V672/2 strange noise

[jokeramik]

I see tantal caps, check them (or did you already recapped them?). They are highly suspicious. This adjustable capacitor (I think it is C203, in the front of the input transformer) could be the problem too.

C203 is for adjusting to best symmetry. If you can´t adjust this. Let it be.
Best regards!

 

[timtom]

What is the best way to clean the connectors? Alcohol?

 

[timtom]

I cleaned all connections and even soldered the boards to the mainboard. the noise floor got better but random crackling still is present. moving the input transformer stops the crackling. I re-soldered the input transformer but nothing changed. I will try soon to swap in a different transformer and will report.

 

[GeorgeToledo]

I did mean to write in my initial post that I’m aware of input transformers going bad on these sometimes, given that you’d potentially been having issues with it. I think it’s the potting/shellac breaking down and interfering with the windings.

 

[timtom]

At this module the replacement of the the input transformer as well fixed the all problems. From 10 Modules 3 suffered from a broken Input Transformer...

I did mean to write in my initial post that I’m aware of input transformers going bad on these sometimes, given that you’d potentially been having issues with it. I think it’s the potting/shellac breaking down and interfering with the windings.

I was suspecting this. I'll try to open one of the transformer to see how they look inside. maybe heating them up helps the potting to stabilize.