Hoffman Amplifiers Tube Amplifier Forum
Other Stuff => Solid State => Topic started by: Cree on November 25, 2018, 10:11:31 am
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Just a question; decided to see if I could find the problem and maybe fix this thing. Very low output on the overdrive channel (what I mean by very low is that you can hear something through the speaker) and no output on the clean (nothing). I have some experience with running a signal and tracing that signal to find the bad component. Yes, I have checked the board, both sides with magnifying glass for loose or bad connections, nothing, no burns or fried circuit components. The amp is built in such away as it will be very difficult to plug up the amp and trace the signal. Question, will I have any luck running a 9V signal and tracing that out OR do I need to power up the circuit? I have provided a schematic and one of a similar amp for the purpose of seeing, "some what", what the circuit board looks like. Plus it has a parts list that matches all of the components, but for a add on board, for effects. Thanks in advance for away forward with this, Or other ideas to help my diy fix. Nothing in it worth keeping other than a speaker and the cabinet, for a tube build. Chassis is to flat, and has a vent grill where one would want to mount tubes, I would think.
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running a signal and tracing that signal
you have a scope, or listening device?
J2 is a stereo jack, basically preamp out, good place to see which way to go.
If you have a mp3 or cd player with volume, jack it into the input, put a stereo headphone in J2 n listen
for a scope I like ~~~100mVAC rms 800hz at input, then just chip in, chip out til things get weird.
I always start with all the DC volts and verify they are as the schematic says, good, onto AC, bad....
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Mp3 input at normal input jack, and no output at the J2 speaker out (headphones) or to the speaker. But if I put the mp3 in the J2 insert, I get a pretty loud, clean, mp3 output to the speaker, with no controls other than the volume on the mp3 player. Messing with the DSP or the effects I do hear a difference with each setting. I'm assuming that board is not my problem. So, I'm looking into a problem with the preamp / mixer of my circuit. Thank you Shooter, for pointing that out to me, totality missed that. I Was sure the main output Transistors where bad.
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so head left to the input, do you have a scope?
If not make yourself a listening amp (should find it here with a search)
also verify your DC volts especially D1 & 2
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do you have a scope?
No scope, I have a DYI headphone and a tone generator deal I use for this. I have not had time to get back to it yet. The world presses on, seams like everything went to heck the day after I took it apart. Getting back to it and digging in, that's on the to-do list for this Sunday. Wanting to have it working by Christmas. But its not looking good right now.