Replacing filter caps

chrisjac2

My old HH VS musician has started making random  farting. Sounds like unplugging a guitar but even when nothing is connected.

I assume the filter caps need replacing as the amp has to be over 40 years old. 

Question  is is this pretty straight forward. Something you can do with little electrical knowledge or is it best left to the professionals? 

I'm reluctant to spend to much on the amp and would prefer to give it a go of poss

ICBM

chrisjac2 said:

My old HH VS musician has started making random  farting. Sounds like unplugging a guitar but even when nothing is connected.

I assume the filter caps need replacing as the amp has to be over 40 years old. 

Question  is is this pretty straight forward. Something you can do with little electrical knowledge or is it best left to the professionals? 

I'm reluctant to spend to much on the amp and would prefer to give it a go of poss

It's very easy on these - just take the chassis out - or top off if it's a head - and you'll see the two caps attached to the rail in the middle. They will probably be visibly leaking, most are now!

Removing them is simple - as well as unsoldering the wires you'll need to break or cut the rivets that were used to pinch the clips together instead of bolts, I usually do it just by jamming a large screwdriver in the gap and using brute force. You can straighten the clip afterwards with pliers if you need to. Replacement caps may be slightly - or a lot - smaller, so you'll need to improvise some means of making them fit, wrapping with tape or a bit of cut-down plastic pipe or something, and replace the rivets with nuts and bolts.

Sounds crude but you can't spend too much time and effort to do a pretty job on them, the amps aren't worth enough (sadly).

jpfamps

I usually use insulation tape on filter caps to increase the diameter if I need to get a modern cap into a clamp.

ICBM

jpfamps said:

I usually use insulation tape on filter caps to increase the diameter if I need to get a modern cap into a clamp.

So do I, but not if the cap is about half the size of the clamp .

DJH83004

jpfamps said:

I usually use insulation tape on filter caps to increase the diameter if I need to get a modern cap into a clamp.

25mm x 2mm self adhesive open cell rubber also does a decent job, wrap around as required to fill the gap plus a bit for compression.

exocet

DJH83004 said:

jpfamps said:

I usually use insulation tape on filter caps to increase the diameter if I need to get a modern cap into a clamp.

25mm x 2mm self adhesive open cell rubber also does a decent job, wrap around as required to fill the gap plus a bit for compression.

Or even 5mm version. Thats what I had to use when I recapped an amp.

chrisjac2

Hmmmm after opening her up there appear to be something that shouldn't be there?

chrisjac2

https://ibb.co/rb5MLdv

ICBM

Yes - the green caps are original, the purple ones aren't. I can't quite see in the pic if the green ones have been disconnected - if they have, then the new values are too small, although that won't cause the problems you're describing (if it's even the caps at all).

If they haven't, then someone has added the extra ones to try to 'improve' the filtering, because the amp was humming. This won't work because the problem is likely to be the caps leaking rather than just not working. If so, remove *both* sets of caps and replace them properly with 4700uF, 63V or higher. If you can use a higher voltage rating or even a slightly larger capacitance to get a larger cap which will fit better in the clamps, I would - the extra cost is more or less inconsequential if you're doing the job yourself.

chrisjac2

Thanks for your help @ICBM I replaced the caps and its all as good as new :-) 

ICBM

chrisjac2 said:

Thanks for your help @ICBM I replaced the caps and its all as good as new :-)

Excellent! Another one saved from the dump .