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 Post subject: TC15 12AX7 channel
PostPosted: Tue Mar 27, 2018 3:54 pm 
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Joined: Tue Mar 27, 2018 3:05 pm
Posts: 2
I have a TC15 that I can't get any volume out of the 12AX7 channel. Every thing looks good except a couple of voltages are high. The cathode voltage for V3 is 3.7v instead of 1.3 and the voltage on pin 8 is 204v instead of 160v. Any ideas?


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 Post subject: Re: TC15 12AX7 channel
PostPosted: Wed Mar 28, 2018 2:14 pm 
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Expert
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Joined: Sat Dec 04, 2010 3:42 pm
Posts: 519
Location: Qualicum Beach, BC
Check the wiring to the V3 socket very carefully. Did you install the jumper between pins 1 and 7?


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 Post subject: Re: TC15 12AX7 channel
PostPosted: Wed Mar 28, 2018 2:41 pm 
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Joined: Tue Mar 27, 2018 3:05 pm
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Thanks for the reply but that is in place.


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 Post subject: Re: TC15 12AX7 channel
PostPosted: Thu Mar 29, 2018 2:29 am 
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Expert
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Joined: Sat Dec 04, 2010 3:42 pm
Posts: 519
Location: Qualicum Beach, BC
Check all the wiring in the 12AX7 channel on the board, tube sockets and front panel. Right from the input jacks all the way to V4. Look for missing connections, parts in the wrong places, bad solder joints and shorts. Make sure all the grounds are good.

If the EF86 channel is working that means the power amp and power supply are all OK. If you can't find any wiring problems it could be a bad tube. Try swapping V3 and V4 and see if that changes anything.


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 Post subject: Re: TC15 12AX7 channel
PostPosted: Thu Mar 29, 2018 11:52 am 
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Holy Ghost
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Joined: Sun Mar 13, 2005 4:10 pm
Posts: 7519
Location: Canada
Good advice. Higher than normal cathode voltages can be a bad solder joint of the cathode pair components.

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