Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: xkaynex on April 16, 2010, 10:26:53 am
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As seen in the photos attached is my DC-30 clone. Used the chassis and turret board from ceriatone but the remaining components were picked up elsewhere. But pretty much followed their wiring layout exactly.
I can't remember how long this has been going on but I can't deal with it anymore. Well from the beginning the Cut pot has never been right. It has to be all the way up for the amp to function properly. As it's rolled back toward 0 the amp just turns to a ham radio. But I just leave it dialed all the way and have been too lazy to fix it. However, even with it up all the way I've been experiencing troubles with the amp just losing all low end. Like if I strum a low chord it will crackle some and then the low end will completely cut out. I've found that if this is done and the amp is "banged on" that will effect it cutting in and out, usually giving that low end back but then it will do the same thing over again once I strum a lower chord. Makes me think there could be a lose connection or cold solder joint or something. But then I still don't know about that Cut switch.
So I'm going to open it this weekend and I just wanted to see if anyone could point me in the right direction of what I should look for first. Any help is appreciated.
Thanks,
Kayne
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a schematic of what you have as-built would be immensely helpful...
--ISO
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Check and resolder your bass cap to the tonestack or if you want you might use a DVM to see if it has continuity on each end of the caps lead and try to make it loose contact with verification from the meter itself
I only go this far because instead of just resoldering a problem i want to know what that problem is for sure even if thats all it may be
Same with resistors. Measure each and everyone before just putting them on a board
Just a habit i developed from making that silly PI 470 ohm - 470K mistake over the years
Not to mention a batch of resistors i got last month that were color coded 100 ohm and they were all actually 47 ohm
I have learned not to rely on a part because it may be new and out of the box
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I just followed Ceriatones layout they have on their website since it's nice an neat.
http://www.ceriatone.com/images/layoutPic/matchlessLayout/Dizzy30Ceriatone.jpg
I definitely think the Cut circuit is the sole problem, I just don't know how. Like
I said, unless the Cut was open 100%, there was signal loss and
scratchyness, just bad all around. I'm guessing that playing the amp loud
would cause the Cut to close like a fraction and that would cause the
crackle. If this was occuring while playing, I could hit the amp a little and it may have
knocked the Cut back to fully open. I tried changing the value of the .0022uf Cut
cap, switched out the Cut pot with a new one, nothing seems to change it. So I just took the cut
pot out of the equation and wired the cut cap right to the Master, which
would just be the Cut open all the way. And that seemed to have solved the
problem completely as it sounds great. What else could it possibly be that when you start to restrict the flow through the Cut pot it sounds nasty??
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Remove the cut pot and cap completely from the circuit. Do not add the cut cap back in. How does it sound?
Still bad, Remove the master as well. How does it sound?
This will help you to absolutely determine if the cut or the power stage master is the problem.