Used WAD KAT88 Issues and Circuit Diagram Request?

[BUTUZ]

Well thanks to bobs generosity I had a known working valve to try and that did not cure the problem.

Me and my dad sat and had a look at the board to try and work out what is going on - there is some very strange work been done to it in the past - traces cut on the board, wrong caps fitted, two resistors cut, and a bunch of extra stuff wired in.

Gonna have to take the board out as we think there's some wiring been done on the top too (judging by the resistor that goes through the board to no where....)

Gonna take us a while to get through each bit. I intend to restore it to the original circuit diagram plus the various reliability changes Greg recommended. (it had had a couple of them done).

That was the last time I use Ebay for HIFI stuff. This is the second amp I've bought that's arrived and I've had to take a screwdriver to. :-/

[bob orbell]

You do find a lot of dodgy sellers on ebay, it may be too late now to take ebay's money back guarantee. Some pictures of the internals may help resolve your problem. Bob

[Phil Y]

Hello BUTUZ,

If the track cuts are on the grids of the output valves, I would leave as they are. I believe the original PCB layout had some "sub optimal" aspects and a previous owner may have done this for good reason. Grid resistors should be wired as close as possible to the valve pin.
A photo would show if this were the case.

Phil.

[BUTUZ]

Hi Phil ok I will dig out my decent camera and take some photos for you.

Thanks!

[Phil Y]

It can be difficult to upload pictures because of the very tight pixel limit. If you are looking at the PCB, it is the pin marked "g1" (grid 1) on the ident of each output valve.

Phil.

[Greg.]

Originally Posted by Phil Y

It can be difficult to upload pictures because of the very tight pixel limit.
Phil.

Indeed. Easiest is to upload images to a free photo hosting site and then copy them across. I find https://imgbb.com is easy to use.

[BUTUZ]

Still more work to do - but much less hum through speakers and no crackling on the right channel any more (phew).

I will need a hand looking at a few mods that have been done in the past - I've taken some decent photos and will post them soon.

[bob orbell]

Nice one BUTUZ ,but I think Phil meant the inside of the amp. By the way, many thanks' for returning my KT88. Bob