5e3 power tube redplateing

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ampmike
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5e3 power tube redplateing

Post by ampmike »

This is a stock mojo 5e3.I started out doing some fixing on a hum,bad preamp tube and the board when I taped on it was real noisy.Thats seems to be gone now but the 6v6 keeps red-plating.I change out the bias resister and the 25/50 cap with it ,no changes.I really dont have a voltage chart the B+ was about 360 on both power tubes.I dont want to wreck any more tubes at this point.Im tempted to pull the board and rebuild,Any thoughts,Mikey
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M Fowler
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Re: 5e3 power tube redplateing

Post by M Fowler »

Well I would check to make sure the cathode bias resistor/bypass cap is grounded and cap positive is wired to pin 8 of each 6V6.

Then I would make sure the screen PS wire from B+ is soldered well, check wire going to screen resistors, check the screen resistors themselves, all connections, and then plate connections. Nothing else to look for other then voltages.

Mark
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Re: 5e3 power tube redplateing

Post by Berger »

M Fowler wrote:Well I would check to make sure the cathode bias resistor/bypass cap is grounded and cap positive is wired to pin 8 of each 6V6.
This was the problem with mine when I had redplating
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ampmike
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5e3

Post by ampmike »

Thanks Guys,Will do,Finally got the master volume in the Liverpool,If you remember Mark ,you showed me how to install it but the filter cap stack was in the way of the hole.Well I got to thinking maybe I could carefully cut two caps loose from the silicone and slip the dual pot in.It worked!!!For some reason I for the last few months thought I had to remove the whole stack.This amp sounds pretty nice!Ok Im headed to the 5E3,Thanks Buddy,Mikey
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martin manning
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Re: 5e3 power tube redplateing

Post by martin manning »

And make sure the 220k grid leak resistors in the 5E3 are well-grounded.
Firestorm
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Re: 5e3 power tube redplateing

Post by Firestorm »

Some tubes will not like the 250Rk.You could go 300. But first check the ground and connections on the 220K grid loads. That could make a tube run away, too.
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M Fowler
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Re: 5e3 power tube redplateing

Post by M Fowler »

Yes I forgot to mention the 220k grid leak.

Darn good thing you guys are around to keep me in line. :)
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randalp3000
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Re: 5e3 power tube redplateing

Post by randalp3000 »

Your thread said tube not tubes.

Is it one tube, and if so did you swap them? New tubes are a crap shoot these days and one could be way out of spec.
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ampmike
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Thanks Guys

Post by ampmike »

You guys are awesome.Pin 6 on the power tube has the under the board wire going to the 220k.Gave it a tug and it had come out.She sings like a bird.Thank You very much Gentleman,2 fixes in one day,Halelujah!!!
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Firestorm
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Re: 5e3 power tube redplateing

Post by Firestorm »

Martin wins.
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martin manning
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Re: 5e3 power tube redplateing

Post by martin manning »

Lucky guess ;^)
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