yes I think so.
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Marshall JCM 25/50 Low Volume & Distorted
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Distrat I tried your advice on connecting a cable from the send of the JCM 25/50 to the return of a different amp and it seems to be working just great. Lots of volume and a nice clean tone on the clean channel and a nice gritty tone on the lead channel. I will apply voltage to the output transformer secondary and measure what I get on the secondary.
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Am I overlooking something? You seem to be concerned your voltages may be wrong, but I don;t see a description of what you are trying to fix. I mean measuring voltages is great, and testing the OT for whatever is fine, but what is the goal?
You report that patching across the FX loop with a cord results in great sound. Are we to assume then without the cord it does not? In which case the return jack needs service, not the transformers.Education is what you're left with after you have forgotten what you have learned.
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while testing a output transformer with voltage will tell you the ratio,
you may have better results with a simple tester you can build. find it at
New Page 1
go to " Tube Guitar Amp Tech Pages "
then " Transformer Short Tester - transformer busted? Find out! "
will tell you if it has shorted turns, which is what i suspect is the problem.
dave
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OK, all the more reason then...
If putting a cord from FX send to FX return restores good strong sound, then you have the VERY common problem just about any amp with an FX loop can have, a bad return jack. The cutout contact in the jack is likely dirty.Education is what you're left with after you have forgotten what you have learned.
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Hi Enzo, I used a cable from the send jack on the Marshall to the return jack on my Peavey Ultra 112. It had a lot of volume and nice tone. I tried using a jumper cable earlier on the effects loop jacks on the Marshall with no improvement in operation. I hope this makes sense.
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Originally posted by Familyortiz View PostJust thought I'd ask... did you look for the obvious, like broken solder joints or other?
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A good visual inspection is always good, but you cannot always see a failed solder connection. best to reflow with a bit of fresh.Education is what you're left with after you have forgotten what you have learned.
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I tried connecting the send effect loop on the Ultra 112 to the return loop on the Marshall. Still very low volume. The volume is as low as using the Marshall itself. I removed the power tubes, drained the filter caps and used the Anatek Blue Ring tester on the secondary windings. Moderate Q reading. I then tried the Anatek on the primary output transformer windings with a moderate Q reading. I'm going to try injecting a small AC voltage into the secondary windings tomorrow and see what the primary readings are. I found a test that Enzo recommended on a similar thread. Any other ideas?
I did try a brand new pair of EL34's as well with no change.
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