Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Twosteps on November 15, 2018, 07:14:13 pm
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So.... I was using a multimeter to measure the current and then decided to measure the voltages as well while I was at it. Forgot to move the red probe on the meter and shorted the circuit twice...(yep that's what took me to realize that I haven't move the probe) :rolleyes: what damage that can cause by this? I have an impression that it might still be fine but right after that when i play through the amp first I've noticed earlier breakup - kind of lesser power and then it got a bit better the second time(turn the amp off and then on again), and better(cleaner) the third time.... not sure what could be wrong with the amp. Other than that everything else is fine. Any idea about which part should I check? Thanks.
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Might want to check your meter. You stand a better chance of damaging that than your amp, I believe.
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Need to know... What voltage were you trying to measure?
If you were trying to measure plate voltage on the output tubes, you put a short to ground on the plate lead of the OT. TWICE! There's a good chance the OT primary is damaged now. Check the resistance between each plate lead and the primary center tap. They should be about the same resistance.
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Gosh, that's what I'm worrying Sluckey... it affected the headroom right away. Yes I was measuring the plate voltage of the two power tubes, zapped one but still... went on to zap another one.. what an idiot.
I did check the resistant afterwards though came in at about 38ma both(one more and one less), so probably still safe here? :sad:
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Measure resistance. Not current.
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:l2: haaaa, sorry got it mixep up - replied in a hurry. Thanks for the advice, will do as soon as I get home.
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One is 212ohm, one is 216ohm - close enough? :w2:
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Yes. :icon_biggrin:
That's normal, 1 side is always a little larger because of the way it's wound.
The 2nd 1/2 after the CT has to go farther around the bobbin and 1st 1/2 wind. So for the same turns/winds the wire is a little longer, so a little more resistance.
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Well, that's a relief. Thanks guys! The sound still not exactly the same the volume kinda came back to where it was but with more noise and earlier breakup but that could be anything as well... tubes or maybe even the wall wart. Although I'm pretty sure it affected the circuit somehow but gonna let it go since the critical parts are still safe...