exxos's Atari, Amiga & retro forum

stephen_usher wrote: 09 Jun 2021 14:19 I'd have thought that you'd have a 470uF in stock as they're so ubiquitous.

I do, but like many, many other things at the moment, they are in a box, and in storage due to the house move, hence having to order some.

To be fair, I need axial and the ones I have in storage are not, though it hasn't stopped me before.

And here's the keyboard and top case after a wash:


The colour is really quite good, and I'm looking forward to getting the power board sorted so I can test if it powers up ok.

There's the usual UHF, Composite & RGB out, so although I can't test the composite, as the model B uses a BNC connector and I don't have an adaptor for the phono of the Elk to BNC, the RGB SCART lead for the Beeb should work just fine.

Already eyeing up the ELK64SD adaptor for extra RAM/ROM space and SD card for disk images.

For some reason I went more traditional path, and I have Plus 1 and Pegasus 400 floppy interface, but to be honest Mega Game Cartridge does equally great job.

arkadiusz.makarenko wrote: 09 Jun 2021 22:27 For some reason I went more traditional path, and I have Plus 1 and Pegasus 400 floppy interface, but to be honest Mega Game Cartridge does equally great job.

Interesting, I'll look that one up, but think the Elk cart will be the one I go for. It is sometimes nice to have the original floppies, which I do for my A8s and C64.

Somehow since I moved into this rental, I've acquired 2 BBC Bs, the Electron and an Amstrad NC100. I'd better stop for a bit so we can move into the new house and I can get my workshop and retro room set up!!

Ok, so good news/bad news on the Electron Front.

The caps arrived and I now have good power, however it's not all roses.

The screen looks like this:


So more troubleshooting required, but it's a start, because it shows me that the video circuit is working, and it's also likely the CPU is good too, and a quick check shows me that the clocks seem good too.

So at this point I'm thinking RAM, but can't discount ROM or possibly the ULA.

I think RAM at this point unless anybody has any other thoughts?

Well, RAM is the most common thing to fail, so out with the toy scope and look at the data pins on the RAM chips!

stephen_usher wrote: 11 Jun 2021 13:46 Well, RAM is the most common thing to fail, so out with the toy scope and look at the data pins on the RAM chips!

Lol, must have read my mind:)

I've broken out the frequency counter and I have 16Mhz at pin 49 of the ULA, and 1Mhz at the 3 clock pins, so in and out, on the CPU. /RESET is high at the CPU too. Since I'm getting a signal on screen, I have to think that the ULA is ok, and it's trying to run, but it's crashing because of the RAM being bad.

Scope will be next, but have to do some work first.

But... "work" is a four letter word! (But so is "play". ;-) )

stephen_usher wrote: 11 Jun 2021 13:55 But... "work" is a four letter word! (But so is "play". ;-) )

I know, but I have a new house to pay for!

Ok, so the service manual suggests that DRAM is the problem, based on the diagnostic chart found on page 20, which fits with what I'm seeing on screen and the other diags I've done.

So, new RAM is ordered, my major annoyance now is actually determining which RAM chip, or chips, is the culprit, since the service manual doesn't give any hints and just says 'Faulty DRAM or broken track; replace.

I know there are only 4 chips, but I'd rather not kill any good ones if I can avoid it.