V76 TAB problem, again...

[dreamix]

I used it mainly as running line level signal through so I didnt got over 24db, but I know everything was working ok several years ago.

Now, when I switch over to 34 db and beyond, the frequency response change and I get alot midrange, like telephone, I tried swapping out the tubes but same problem

I have replaced capacitor 12 , 13 , 35, ...so far

Any ideas? or keep recapping

 

[rock soderstrom]

Any ideas?

Defective transformer/choke with partial short-circuit of one of the windings?

or keep recapping

Try to follow a test signal with a scope or sniffer and see were you lose bandwith

 

[dreamix]

Defective input transformer with partial short-circuit of one of the windings?

Try to follow a test signal with a scope or sniffer and see were you lose bandwith

The weirdest thing is it seems to actually be Adding mids, LF is still there, not sure about HF...

Ye I guess I have to take it down to our local repair shop, I dont have a scope...

 

[rock soderstrom]

Ye I guess I have to take it down to our local repair shop, I dont have a scope...

Yes, I think it's better to search for the error systematically with the right equipment. I'll keep my fingers crossed that it's just an old faulty capacitor and not one of the expensive iron.

 

[dreamix]

Yes, I think it's better to search for the error systematically with the right equipment. I'll keep my fingers crossed that it's just an old faulty capacitor and not one of the expensive iron.

btw, if its the input transformer, wouldnt every gain setting be affected? I never understood the circuit/design... first... there is one tube only up to 24 db?

 

[rock soderstrom]

btw, if its the input transformer, wouldnt every gain setting be affected? I never understood the circuit/design... first... there is one tube only up to 24 db?

Yes, I understand what you mean. I agree, but I'm not an expert on this circuit. On the other hand, a buddy had similar problems years ago and the IPT was shot.

Let's not assume the worst for now and hope for the best. Check your treasure systematically and you will see relatively quickly where the problem lies.