I have a board and parts on the way. based on folks here, I decided some while ago this would be worth having, and whenever that happens with a preamp,
I end up wanting two of them anyway. That way I can have one upstairs and the other downstairs.
Also, this one is in a much larger case than I normally use, and did that on purpose, but the second one will be more compact. The luck I have been having, I may only end up with one functioning! It would be gravy if I can salvage this one for the second.
looking a little better for this one, but not out of woods yet by a long shot.
I end up wanting two of them anyway. That way I can have one upstairs and the other downstairs.
Also, this one is in a much larger case than I normally use, and did that on purpose, but the second one will be more compact. The luck I have been having, I may only end up with one functioning! It would be gravy if I can salvage this one for the second.
looking a little better for this one, but not out of woods yet by a long shot.
Also, how does one measure Vbe in the BC transistors? Looking at board pic in Guide to locate on board now.
As we face a BC transistor its pins are CBE from left to right. So Vbe is the dc voltage between B,E.
Is it possible that your build is generally fine and you simply wired something wrong? Is there someone you know with a generator and a scope plus compatible op-amps to swap, or even better someone who has built a DCG3 before to inspect your build? Even the J1s,J2s can be substituted with 2SK/LSK 1xx if your uPAs health isn't sure. By the way, if you will ever remove the uPAs you can put female pin rows there for easy input JFETs swaps and tests.
Found them Q1 and Q2.
Oh, just a multimeter, ok. I thought I needed something other to test. no problem.
Let me get some clear pics. Its in a large case and I used the same layout as others here have. I will install those female pin rows on new build, or this one if they need removed.
Hopefully these help. I have disconnected the preamp out cables, and removed the leads to the pot, but all else is as was. Let me know if better pics are needed.
Attachments
Healthy. Until now you did not measure worrying voltages anywhere.
Will try to look at the pics in detail later. Meanwhile if anybody else spots something odd should let you know. There are many DCG3 owners who know the practical build details even better than me.
No, just thisoffset thing. I really thought I would find where I had mixed up two similar looking devices, but not yet. It was doing all this all of a sudden like. On first fireup, it was just as guide said. got close to 0, then powered down and installed AD823. THEN, I had to jack around trying to fudge an input. I keep waiting for that moment when I find the stupid mistake....but it is hiding good. This initial testing was all done without board wired to pot, outputs or inputs.
It was after that I couldnt get sound, and then saw the counting offset. I have watched it go all over the place, digit at a time, all the way down to 0, then begin -1, -2, -3, all the way up. I turn it off as soon as these measurements are taken. Sometimes I'm not sure if I am really measuring that, or if the meter is just reacting to itself. (yes, new battery and tried different multimeter. The heatsink gets slightly warm, transformers are room temp. The pots adjust noting that I can tell.
Yes. I have used this I-select and same pot in my other preamps. Lines come into pot from I select pads to pot input, then from pots outputs to boards in/G.
When initial fire up without AD823 all was well. Same after AD823 installed. Then I wired outs on board to RCA outs, and pot outputs to board inputs.
Problem happened as to power to the I-select, I needed to remove power supply to get to underside of board, and to do that all the knob, extender post,, switch and it's mount had to be undone. Like an idiot, I thought I could quickly make an input bypassing the I-select using the "out" pad on I-select behind the volume pot pad.
After failing and deciding to power I-select properly, I wired everything up, no sound again.
Started measuring everything, but all measures as it should with the exception of off set. It will not stabilize, meter keeps varying, increasing or decreasing.
And here I am!
When initial fire up without AD823 all was well. Same after AD823 installed. Then I wired outs on board to RCA outs, and pot outputs to board inputs.
Problem happened as to power to the I-select, I needed to remove power supply to get to underside of board, and to do that all the knob, extender post,, switch and it's mount had to be undone. Like an idiot, I thought I could quickly make an input bypassing the I-select using the "out" pad on I-select behind the volume pot pad.
After failing and deciding to power I-select properly, I wired everything up, no sound again.
Started measuring everything, but all measures as it should with the exception of off set. It will not stabilize, meter keeps varying, increasing or decreasing.
And here I am!