Marshall 4101 overheating
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Superhorndog
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Marshall 4101 overheating
Working on a 4101 combo. Just finished a recap and biased in a new set if EL34's at 32ma. Amp is running a 440v plate voltage. Sounds good except it wants to run hot after 15 minutes or so. Main filter capacitors are at 200 degrees which is way too hot. Stock ones were replace with F&T's. Wiring is all the same. For the life of me I can't figure out why they are running hot like that. I seem to have correct voltages everywhere as far as I can tell.
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sluckey
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Re: Marshall 4101 overheating
Good filter caps run at room temp. If they are not being heated by radiant heat from a nearby transformer or power resistor, then the caps have internal issues or you have a wiring error.
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Superhorndog
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Re: Marshall 4101 overheating
I'm thinking these caps are the issue. I took before pictures as I always do before I changed them and they are 100% wired correctly. I'm going to order up some JJ filter caps as I typically use those and have never had an issue.
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Stevem
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Re: Marshall 4101 overheating
Are you seeing the V+ sink as the filters get hot, as that would be the case if going bad, and also there uf value would be measurably less and you should see the AC ripple voltage at the first filter node rise as they get hot if they are bad.
I would idle the outputs very cool for a while and see if that temperature rise does not take place, if so leave the amp on for 4 to 5 hours and see if it’s just a matter of giving the new filters time to form.
Of course if you still have one of the old ones and it does not look or test leaky you can put one back in and see if it stays cooler then the new F & T .
I would idle the outputs very cool for a while and see if that temperature rise does not take place, if so leave the amp on for 4 to 5 hours and see if it’s just a matter of giving the new filters time to form.
Of course if you still have one of the old ones and it does not look or test leaky you can put one back in and see if it stays cooler then the new F & T .
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Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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Superhorndog
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Re: Marshall 4101 overheating
No drop in V+. I'm biased at 60% dissipation and still the caps get hot. Just recieved some new caps. Going to check the amp draw before I switch them out.
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mrfreddieboy
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Re: Marshall 4101 overheating
@Superhorndog
Were the F&T caps faulty?
How did the new caps work out?
I find this a puzzling problem since presumably the filter cap didn’t run that hot before. My initial guess would be a faulty cap maybe having its voltage overrated or some internal short or something.
Fred
Were the F&T caps faulty?
How did the new caps work out?
I find this a puzzling problem since presumably the filter cap didn’t run that hot before. My initial guess would be a faulty cap maybe having its voltage overrated or some internal short or something.
Fred