Noise when you tap the chassis or any component!

[tonyhelton53]

I'm trying to repair this 18 watt kit amp for a friend. I don't think he built it, but I've already tried re-flowing practically every solder joint, and reinforcing grounds by soldering with high heat iron to chassis. I thought it could be the filter cap, because I've seen them make an almost identical sound, but that wasn't it. Still has the same old crrracck! when you tap the chassis, or even the workbench I have it sitting on. I have replaced all the tubes, with the exception of the rectifier. Any ideas? Any help would be greatly apprecitated.

[JMPGuitars]

Hi,

We need info and detailed photos. For troubleshooting, start with the stuff in my signature.

Thanks,
Josh

[Bieworm]

This can imho only mean 2 things:
1. Microphonic tube
2. A bad ground connection

I suspect the latter

[tonyhelton53]

Thanks for your input. I'll keep chasing those grounds!

[Bieworm]

can you post some detailed photos so we can take a look? IME ground busses are notorious for bad ground connections. When I solder a wire or component to a ground buss I wrap the wire 2 times around the buss and solder it to the buss while pulling on the wire. That turns out the most successful for me..

[tonyhelton53]

I'm new to the forum, and it's telling me I can't register because my email already has been used - and it's ME! I'll try to straighten out the misunderstanding and post some pictures. Thanks, TONY

[JMPGuitars]

I'm new to the forum, and it's telling me I can't register because my email already has been used - and it's ME! I'll try to straighten out the misunderstanding and post some pictures. Thanks, TONY

Why would you want to register again? You're already here / active.

[tonyhelton53]

That's what I thought, before it will let me post pictures it says I have to register! Which I already have. I've been having some medical issues and just got back online today.

[Daviedawg]

If you have remade all the connections and swapped the valves the next step is to examine all the bolts and ring nuts fixing hardware to the chassis since banging the bench makes it resound. Then chopstick all the wires carefully without tapping anything, looking for a broken conductor.

Dd

[tonyhelton53]

Thanks for the reply. I'll try that.

[tonyhelton53]

After chop-sticking very delicately around components on the board, the only thing that stood out as being worse noise was around both of the 16 microfarad 500 volt caps. So I replaced them and hot doggies it fixed it! After gloating a little a playing through this little amp I figured out that the overdrive channel that was added didn't work any more. So got the chop stick and I found a wire broken off the pin it was soldered to. When I jiggled it and it made contact it started feeding back ( I had the volume all the way up). After re-soldering the wire I'm calling my buddy to pick it up!
Thanks to all you guys that responded to this post. You helped me immensely! TONY HELTON