Problem with cathode resistor

liberty · 8th September 2005, 02:31 PM

I have a single ended amp lo scherzo and it run good since 1998. Now there is a problem in one channel, it doesn't make sound and burn the cathode resistor. I changed the tubes and the resistor but it burnt again. I measured all parts and amp checked good. The question is, what to do?

Thanks a lot for any suggestion.

Lo scherzo

amperex · 8th September 2005, 04:49 PM

How about a poor tube socket that does not provide good contact to the tube bias pin?

Tube_Dude · 8th September 2005, 05:29 PM

Hi

Inspect if C3/4 are not leaky and if R15/16 and R9/10 are not open.

Ciao.

Geek · 9th September 2005, 01:37 AM

If the above mentioned components are good, use an AC voltmeter or (preferably) 'scope to look for a nasty HF oscillation. If that's the case, check the PSU caps.

8th September 2005, 02:31 PM	#1
liberty diyAudio Member Join Date: Jul 2004 Location: Ancona	Problem with cathode resistor I have a single ended amp lo scherzo and it run good since 1998. Now there is a problem in one channel, it doesn't make sound and burn the cathode resistor. I changed the tubes and the resistor but it burnt again. I measured all parts and amp checked good. The question is, what to do? Thanks a lot for any suggestion. Lo scherzo

8th September 2005, 05:29 PM	#3
Tube_Dude diyAudio Member Join Date: Mar 2002 Location: Aveiro-Portugal	Hi Inspect if C3/4 are not leaky and if R15/16 and R9/10 are not open. Ciao. __________________ Jorge

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8th September 2005, 04:49 PM	#2
amperex diyAudio Member Join Date: Feb 2005 Location: MI	How about a poor tube socket that does not provide good contact to the tube bias pin?

9th September 2005, 01:37 AM	#4
Geek diyAudio Member Join Date: Sep 2004	If the above mentioned components are good, use an AC voltmeter or (preferably) 'scope to look for a nasty HF oscillation. If that's the case, check the PSU caps.

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