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?





IMO, reduce the capacitor value will has a bigger impact in sound quality, those 220uF capacitors are mounted into a 35mm clamp with point to point soldering. You need to find a 50uF cap with similar quality and diameter to fit into those clamps or you need to find a way to mount them into the chassis if the caps has different dimension. And the modification cannot be easily reverted!

OTH, install two UF4007 on the rectifier tube socket is a very simple job ( it takes less than 10 minutes ) and those diodes only cost a few dollars. Its also very easy to reverted.

Those diodes are functioned as a protection device to reduce the chances of rectifier tube arcing and also can prolong the life of those rectifier tube. BTW, the effect in sound is negligible.

My suggestion is go ahead install the diodes first, put in some new rectifier tube and see if it solve the arcing problem. If you don’t like the result, then go for the capacitor mods or install soft start device.

BTW, always wait as least 5 minutes to let the tubes cool down before you switch the amplifiers on again as @dekay suggested.




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

You have contributed nothing useful to this thread (instead you have performed as a cheerleader with your +/- opinion of those who have contributed useful info/avenues of thought).



@imhififan good point.  I also have considered those points, especially I am not that technically inclined.  


also to make sure, the diodes should be added at pin 4 and 6 as shown in the second diagram above, with the line on the diode closer to the pin, am I correct?

Yes, I found a picture on the web that show the details

You can solder the diodes on the socket and move the wires accordingly. you can use 1N4007 diode, but UF4007 is better (lower noise) and just cost a few cents more.

BTW, if you interested add on a NTC soft start device please let me know, it just cost less than $20 in parts. Since it will be bypassed in 10 second after power up, it will not affect sound quality.