Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Stuff4bikes on July 02, 2021, 02:12:52 am
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Schematic is from this site...
When playing open cords amp sounds very fuzzy, fizzy, distorted even at low volumes.
As stated above schematic is from this site.....only changes are 20uf 20uf 16uf
And 0.1 caps are .01 caps.
EH AY7, EH AX7. Matched set of CBS 6V6GT's, Sylvania 5Y3..
All these tubes sounded good when played through my champ circuit.
It sounds bad on all the speakers played through so far.....
I only have guitars with humbuckers and P90's sounded fizzy with both.
One issue I would like to point out is the PT and OT are from a philco console
The OT in it's original form used resistors on the output, so I tried 2 other OT's
And same fizzy sound.
I read where someone had cooked the 500pf cap on the tone pot and had similar issues.
I think I will start with the pots and work from there.
Oh.....there doesn't seem to be any loss of volume.
380 on the plates
350 screens
Ay7 133 and 133
Ax7 185 and 270, 250.
Thanks for any help.
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I read where someone had cooked the 500pf cap on the tone pot and had similar issues.
Is it a silver mica cap?
A member here, not long ago, had to replace the silver mica tone cap twice. The 3rd cap resolved the problem.
Silver mica caps seem to get cooked sometimes when they are installed. Use a heat sink and get in and out quickly.
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Mine is not a mica, it's just a generic yellow cap.
What's giving me fits is, even though it's fizzy
The volume doesn't seem to be affected.
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Photos of the build?
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Photos of the build?
I can't get any photos until Monday. I am out of town for a wedding.
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Is it the standard chassis, anything unusual about the layout?
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Is it the standard chassis, anything unusual about the layout?
The chassis is all aluminum 2 piece. Standard 2" deep 12x8 with the control panel riveted to the chassis.....similar to the 60's bogen chassis. Controls are grounded to the chassis by a solder lug bolted down. Control wires run from underneath through a hole in the chassis and are landed on the control panel.
I think I have figured out my problem....
Probably should have mentioned earlier....I am using old pre amp tube sockets....I wanted shielded tubes so I used some I had laying around. I think those might be the issue.
At any rate thanks for letting me air out my issues........
I am no pro at this but I guess I got lucky the first few times I built an amp....BUT I used all new parts on those, last two I built have been with old used stuff..and have given me the fit's.
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Old socket could be rusty or oxydized. Try to clean them with Deoxit contact cleaner. Push and pull tubes in and out in socket many times.