Puzzler

krzanik · 26th April 2007, 04:36 AM

I just completed a single ended 6V6GT amplifier. I followed the schematic correctly (so I think) but when I turn it on I get music from one speaker but not the other. The really weird thing is when I turn it off I get music from both speakers for a few seconds (before the amp powers off completely). If I quickly turn it on again I get music from both speakers for a few seconds and then one fades away leaving one channel with music. Is this indicative of a particular problem? I'm so confused. Any help would be greatly appreciated.

tubelab.com · 26th April 2007, 01:01 PM

I saw this problem before. In my case the resistor from the grid of the output tube to ground (or the bias supply) was open (physically broken). I suppose that this could happen in any stage. Check the resistances to ground through each stage in the amp. Just compare the good channel to the dead channel. Make sure the power is off and all electrolytic caps are discharged.

krzanik · 26th April 2007, 06:15 PM

Thanks for the information. I figured someone would have had this happen before. I'll try to check the dead channel out tonight and see what I find. I hope your right and it's simply an incomplete connection.

krzanik · 27th April 2007, 12:47 PM

I checked out the dead channel last night and couldn't find anything wrong with it. Finally I replaced the 12AX7 with a new one and both channels seem to work fine. The origonal 12AX7 was a used old stock RCA that I guess wasn't working.

Thanks for your help.

26th April 2007, 04:36 AM	#1
krzanik diyAudio Member Join Date: Jan 2005 Location: Austin, TX	Puzzler I just completed a single ended 6V6GT amplifier. I followed the schematic correctly (so I think) but when I turn it on I get music from one speaker but not the other. The really weird thing is when I turn it off I get music from both speakers for a few seconds (before the amp powers off completely). If I quickly turn it on again I get music from both speakers for a few seconds and then one fades away leaving one channel with music. Is this indicative of a particular problem? I'm so confused. Any help would be greatly appreciated.

26th April 2007, 01:01 PM	#2
tubelab.com diyAudio Member Join Date: Jul 2005 Location: South Florida	I saw this problem before. In my case the resistor from the grid of the output tube to ground (or the bias supply) was open (physically broken). I suppose that this could happen in any stage. Check the resistances to ground through each stage in the amp. Just compare the good channel to the dead channel. Make sure the power is off and all electrolytic caps are discharged. __________________ Too much power is almost enough! Turn it up till it explodes - then back up just a little.

26th April 2007, 06:15 PM	#3
krzanik diyAudio Member Join Date: Jan 2005 Location: Austin, TX	Puzzler Thanks for the information. I figured someone would have had this happen before. I'll try to check the dead channel out tonight and see what I find. I hope your right and it's simply an incomplete connection.

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27th April 2007, 12:47 PM	#4
krzanik diyAudio Member Join Date: Jan 2005 Location: Austin, TX	I checked out the dead channel last night and couldn't find anything wrong with it. Finally I replaced the 12AX7 with a new one and both channels seem to work fine. The origonal 12AX7 was a used old stock RCA that I guess wasn't working. Thanks for your help.

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