2. amps-preamps
  3. 175372-13968

Is rectifier tube arcing a problem?

I did some research and couldn’t find a definite answer.  I have an amp that I tried 6 different pairs of 5U4G and 5U4GB. 3 pairs has arcing (RCA 5U4G, TungSol, Svetlana 5C3S) and 3 pairs don’t (RCA 5U4G with hanging filament, EH 5U4GB, Sylvania 5931).  I took the amp to a technician and he checked everything, he can’t find anything wrong.  The problem is, I like the sound of the TungSol and Svetlana which both have arcing.  The technician said it is ok to keep using them, but honestly I am not too comfortable.  But I like their sound.  Is it really ok to keep using the arcing tubes?  Will it damage the amp?

 

 

gte357s
gte357s OP
281 posts
 

@imhififan thank you. This seems something small and won’t change the sound.

min the diagram, I need to add two diodes per tube, am I correct?

imhififan's avatar
imhififan
2,142 posts
 

I need to add two diodes per tube, am I correct?

Yes.

BTW, do not reuse the arced tube! Usually once a tube has arced It will continue to arc at that same spot on power up.

 

fiesta75
1,378 posts
 

Finally, some real help for this problem. Thanks for helping to solve problems that the wannabees simply cannot.

atmasphere's avatar
atmasphere
11,656 posts
 

min the diagram, I need to add two diodes per tube, am I correct?

Yes.

I agree something is up in the amps- the 5U4 should easily handle the load all on its own. It sounds like something is causing an excessive load during warmup, which is a classic symptom of the filter capacitance at the output of the rectifier being too large. Both doing the same thing is not coincidence! What is the capacitor value at the output of the rectifier tube? There is no schematic in the manual...

imhififan's avatar
imhififan
2,142 posts
 

@atmasphere

This is the power supply schematic at Steve Hoffman Forums, not sure if OP’s kit has the same power transformer (C core) and same component value?

 

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