Originally posted by AL78
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I think ee established his meter won't work here
AL78- I didn't expect you to interpret the meter drawing quite so literally. No cutting of probe leads is required So long as (1) the capacitor ends up in series with the meter - use clips, wire or whatever and (2) you cannot touch the side that will be probing the amp ( high voltage risk ) it will be fine.Experience is something you get, just after you really needed it.
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I do as was described above and I use the free cap lead as a small probe. But for the less experience, I would ground my black probe to chassis then clip a wire to the red probe tip and to the cap, then use another clip wire from the other end of the cap. Now I use that second clip wire as my probe. That way I do not have to hold the cap in my fingers while touching potentially dangerous voltages.
My Fluke meters do not need this trick, but I still wind up doing it now and then when some situation arises. A cap is also a good way to block DC if you want to inject a signal from your generator into the signalpath at some point with DC voltage on it.Education is what you're left with after you have forgotten what you have learned.
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While you wait, there are a couple more areas you check do that I just thought of.
You can do the signal generator / ACV measurement on either side of C43, and either end of VR4. Also take the PCB out and have a really good look at the V1 and clean tone control stack areas for bad joints.Experience is something you get, just after you really needed it.
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c43 I'm giving 362mv I'get 20mv more or less both sides.
c41 16mv and 9mv c40
I have a question it's R19 the output of the tube?I don't know if we checked either ac or dc
I've checked with continuity test and a magnified glasses the board everything looks goodLast edited by AL78; 03-06-2017, 09:05 AM.
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That doesn't make sense. You apparently have a big signal on C43 but not on C40 and/or C41? That's not possible. Recheck where you are probing
IF we take the C43 measurement of 362mV and IC5 pin 2 at 7mV as correct from earlier, then there is an open circuit between C43 and IC5 pin 2. I would expect around 80mV on IC5 pin 2. Measure the DC resistance from IC5 pin 2 to ground and to the C43/R45 junction.Experience is something you get, just after you really needed it.
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So since there was some confusion I've redone the test for c43 I connect the pc with a 1000hz 362mv and I get more or less 20mv(as said before)either side
and I get 16mv for c41 and 9mv for c40.To do the second test (c40 c 41) I had to flip the board because those caps have no room to probe.If you think that the c40 c 41 test is not good Please tell a point where I can check again.I have continuity between Ic5 pin 2 and c43 and r 45.Thanks
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