54510-a Sound Amplifier recap

[mttweeks]

I repaired this amp by recapping the power supply and repairing a few traces. I decided to also recap the rest of the amp. Only thing holding me up is the 2 large capacitors. They are Mallory 3000uF caps and I cant find many matches. I have found screw in termination style with the same specs but they are larger and not made for audio equipment. Replacing these scare me because one of them has what I believe is the positive leg wired directly to the case. Does anyone have an idea of a better replacement option and an explanation of why it is wired to the chassis? Also just to confirm, the middle lug is positive, right?

[jukenorman]

You will get 3300uF at Mouser (world wide) easy enough although maybe not the twist-lok that the originals are (I haven't checked). Yes the +ve of one goes to ground, just make sure the case is isolated from the chassis like the originals.

Norman.

[mttweeks]

Case of the capacitor? I am not familiar with these caps. Any amp or stereo I have repaired has typically been modern radial or axial. Im assuming I am going to have to get radial pc pins unless I get lucky and can find solder lugs. Which will probably require a bracket to mount them.

[jukenorman]

Twist-lok capacitors are normally quite expensive. I can see from your pictures that there are already isolation pads where the capacitors are fitted. It also depends on the capacitors that you buy - some have metal cases (or thin plastic easily scratched coatings or paint on metal cases) which are connected to the negative terminal. You wouldn't want to use that type for the positive ground without taking good care of the isolation. You also get plastic clamps for mounting can (radial) capacitors and I often use these in that type of situation to maintain good isolation from the chassis. I'm not really sure how "modern" really changes anything?

Norman.

[jukeboxmarty]

There are PCB's manufactured that allow radial caps to be mounted to the chassis, to replace twist lock cans.

You can install one or more capacitors.

A quick search on the internet yielded this result, but similar boards are available from many sources.

I'm not sure if this is the size you need, you'd have to check it out. I'm sure someone makes a PCB similar to this for the smaller twist locks.

grangeramp.com/product/multi-section-capacitor-board/