Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: kfs90 on January 26, 2017, 05:35:20 pm
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So, I went off the Ceriatone diagram here. New tubes in and turned it on and it caught fire around the first resistor on the left side of the board that connects to the diode and the rectifier tube. Idk anything about theory, so if anyone can help with what went wrong, I'd really appreciate it.
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Fuses didn't blow...
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Wow! Got a video? :icon_biggrin:
Recheck your wiring. Something is not right.
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Yep, something is connected where it shouldn't be. Or maybe the diode connected to that resistor is backwards.
No way for us to know without seeing good quality photos of your amp.
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The only thing different is that I took the half power switch out of it and used this Triode setup by the power tube section.
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If it was wired like either of those layouts it would not burn.
Recheck your wiring. Something is not right.
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And did you use the bias pot shown on the 2nd layout?
If you did and got a wire to the wrong turret, it could make the resistor burn.
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I was so exited with my first build....turned the power on getting ready to rock....then the smell......then smoke.....damn!!!
You will isolate it but take your time. I had a short in my power rail. :BangHead: I've gotten better at soldering.
Bart
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This is my second build; really a conversion though. It started out as a Ceriatone JMP50 supposedly but was so modded that my tech couldn't even figure out what it was supposed to be. So, I brought it home and converted it to a JTM45.
Turns out the 180k resistor that burned was a 180 ohm that I mistakenly put in. Haha. It turns on without burning, now, but there is a horrid sound almost like a ring modulator. I kept the impedance selector wiring like it was from the previous owner, but can someone verify the wiring? Mine is a different switch from the diagram. The picture is as if you are standing on the front panel side looking towards the inside of the back panel. You can see the power tube socket and where the selector wires to the board as reference points.
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there is a horrid sound almost like a ring modulator
You may need to reverse the OT primary plate leads.
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I just tried swapping them on the tube sockets. Same sounds coming out. Any other ideas?
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Good time to try some live chop sticking and probe the lead dress and maybe separate wires running too close and give them a little breathing room. On a conversion project if it's pretty old, cleaning the tube sockets, pots and switches with contact cleaner is always a good idea. Also substituting known good tubes one by one to see if it makes a difference. Platefire
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Good suggestions. I tried separating close wires, new tubes, and cleaning everything. Still the same bad sound. Could there be anything in particular that would cause this ring mod sound? I swapped a couple values from the drawings with parts that I had here at home. From right to left on the drawings I used a 63v330uf cap where they had a 220 uf 25v and a 500v16uf where they had a 16uf 475v. Would this make it do that? They are all correct direction. There are also 6 of these yellow nos looking caps that the previous owner had in it. If one or some of those went bad, could that cause the problem?
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I swapped some caps in for new ones and tried swapping tubes. Still the same ring modulator sound coming out. Can someone verify that the impedance selector is wired correctly or not? I don't know how this type works. Other than that, here are some pictures.
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More pictures. Let me know if I need to take anything in particular for better viewing.