I was trying some of the modifications from Ingrid with the parallel cap, resistor on pin 7 of V1 and wanted to see what it sounded like after pulling the diode string but when I plugged in and turned it on there was no sound at all. I turned the volume wide open and could only hear a little of the guitar. So I undid everything and put it back the way I had it, except I wired the diode string on V5 backward and blew the fuse. I replaced the fuse and rewired the diode string correctly but still get the same results. No sound except for a small amount with the volume wide open.
I checked voltage everywhere. I'm getting readings everywhere except the heaters to all the pre amp tubes and the Pin 2 and 7 heaters of V4 and V5. I'm afraid I may have blown my PT. Does anyone have any thoughts? Do you think that's what I did and why did none of the mods work in the first place?
Mistake
Moderators: pompeiisneaks, Colossal
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marcoloco961
- Posts: 356
- Joined: Wed Feb 25, 2009 3:07 pm
- Location: Colona, Il. U.S.
Re: Mistake
I think would start by disconnecting the heater taps from the circuit and powering up the amp and checking to see if you have approx. 6.3VAC. at the PT. If the PT is throwing the proper voltage then look for a short in the heater circuit. You might try changing the power tubes for known good ones if available. Is it possible you could have fried the power tube by reversing the diodes? Just a thought.
Re: Mistake
The power tubes are still glowing when I turn it on. Plus I'm getting voltage everywhere else including Bias voltage, all along the pre-amp circuit, filter caps, B3-5 on the pre-amp board, and on the power supply board circuits. The only place I'm not getting readings is on the heater pins of any of the pre-amp tubes or power amp tubes. They are all glowing but no voltage on the heater pins.marcoloco961 wrote:I think would start by disconnecting the heater taps from the circuit and powering up the amp and checking to see if you have approx. 6.3VAC. at the PT. If the PT is throwing the proper voltage then look for a short in the heater circuit. You might try changing the power tubes for known good ones if available. Is it possible you could have fried the power tube by reversing the diodes? Just a thought.
Re: Mistake
I just pulled the heater taps and tested them and sure enough no voltage reading. I think my PT is gone. 
Re: Mistake
Nevermind. It appears that I had the cap soldered in wrong. That was the problem. Everything is fine now. Boy, to be new at electronics...lol