How does a Tube Rectifier fail?

harry · 06-28-2009, 08:49 PM

Never had an amp with a tube rectifier before, so I don't know how they behave.

I'm making an amp with a 5AR4, the power transformer secondary measures 720V ac with a meter (is this commonly labelled 360-0-360?). after rectification it produces 390V. I checked voltages a while ago without tubes and it was giving out 520V.

If I monitor the plate of my EL34s as I play, the voltage slowly drops. I imagine the amp would fade out completely eventually.

So my question is: when tube rectifiers die, do they fade out slowly?

Baxtercat · 06-29-2009, 10:26 PM

I had one go in a Super Reverb [decades ago, before I knew any of this stuff] and it glowed red and took out some filter caps too. It must've had a short.

Enzo · 06-30-2009, 02:31 AM

Does that voltage continue to drop? Or does it only drop a certain amount as the amp warms up? And does the voltage climb back up when you stop making sound through it? That would be normal.

harry · 07-01-2009, 11:02 PM

It continued to drop.. maybe a volt every thirty seconds.

Today it gave up completely and began arcing. Oh well.

06-28-2009, 08:49 PM	#1
harry Senior Member Join Date: Jul 2007 Location: leighton buzzard, uk Posts: 118	How does a Tube Rectifier fail? Never had an amp with a tube rectifier before, so I don't know how they behave. I'm making an amp with a 5AR4, the power transformer secondary measures 720V ac with a meter (is this commonly labelled 360-0-360?). after rectification it produces 390V. I checked voltages a while ago without tubes and it was giving out 520V. If I monitor the plate of my EL34s as I play, the voltage slowly drops. I imagine the amp would fade out completely eventually. So my question is: when tube rectifiers die, do they fade out slowly?

06-30-2009, 02:31 AM	#3
Enzo Senior Member Join Date: May 2006 Location: Lansing, Michigan, USA Posts: 10,366	Does that voltage continue to drop? Or does it only drop a certain amount as the amp warms up? And does the voltage climb back up when you stop making sound through it? That would be normal. __________________ Education is what you're left with after you have forgotten what you have learned.

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06-29-2009, 10:26 PM	#2
Baxtercat Junior Member Join Date: May 2009 Location: Pacific Grove Posts: 18	I had one go in a Super Reverb [decades ago, before I knew any of this stuff] and it glowed red and took out some filter caps too. It must've had a short.

07-01-2009, 11:02 PM	#4
harry Senior Member Join Date: Jul 2007 Location: leighton buzzard, uk Posts: 118	It continued to drop.. maybe a volt every thirty seconds. Today it gave up completely and began arcing. Oh well.

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