A5000 Gone for good? :0

[IanS]

So my current guess is the signal isn't making it as far as the IOC. If I simulate that on an A3000 (removed LK16) then I get similar results. There is the similar initial exchange, we see the response from the keyboard, but the IOC didn't, The OS then tries again a bit later before giving up and showing "keyboard not detected" for me.

Close up of the second exchange.

Can you probe on the actual pin of the IOC chip, to rule out dodgy sockets or other connections.

[nicf82]

Yes, I will give that a try

[nicf82]

So this is KOUT/KIN at the IOC, the Scope's GND is the IOC's GND too so not sure why it is so noisy again.

KOUT KIN at IOC

This is KIN at LK5 vs the same signal at the IOC

LK5 and KIN pin

So it seems to be getting there

[mattwestuk]

Good Afternoon All,

I received my A5000 yesterday. It's not in too bad a condition, and the first thing I did was to replace the battery:

I have also checked the R281/R272 area and it all seems to be working. I've also checked any tracks that look damaged and they are good.

I know I need to scrub the nasty green damage away, but can anyone recommend areas to check after that? Right now when I boot it up, there's no power light (and the 5v terminal that connects to the light isn't getting power (probably because of below).

Keyboard lights do flash, but there's no floppy activity or POST beep. I've also checked the voltage outputs from the power supply and they are all within tolerance.

It had been sitting in the seller's attic for many years, but doesn't look too bad as a result.

Hoping someone can point me in the right direction.

Matt

[IanJeffray]

the first thing I did was to replace the battery:

I hope that's a "before" photo. Get that horrible thing off the board.

doesn't look too bad as a result.

Sorry to say, I think it looks in really dreadful shape. And often board look less bad than they really are. Looks to me like heavy leakage all over the CPU/RAM area and even what looks like burning near the Acorn logo.

It's the rarer "Alpha" board - should be running at 33MHz but it's clearly been overclocked to 36Mhz (72MHz oscillator). It's worth doing the work to save it, but I predict a long road ahead - been there several dozen times...

[mattwestuk]

I'll definitely do the work. I guess I can't complain though, I brought an A3000 a few years back that had zero damage/leakage...I doubt anyone gets lucky twice with these things!

[mattwestuk]

During cleaning, C161 came loose and fell off. I'm looking at the schematics but can't seem to find it. It's has 47, 16A, 38A stamped on it if anyone knows what that is. It's definitely where I need to start.

Here is how the board looks post-cleaning. The missing capacitor is circled.

[IanJeffray]

During cleaning, C161 came loose and fell off. I'm looking at the schematics but can't seem to find it. It's has 47, 16A, 38A stamped on it if anyone knows what that is.

47uF, 16 volt.

[mattwestuk]

Found it and soldered a new 47uF electrolytic capacitor in and checked conductivity. It is good, but still nothing other than noise on the speaker (not even the power light). The cap is good as I metered it before I put it in.

The full schematics I found online are great, but they don't show what to expect on each pin/line. Oh how I miss the simplicity of the BBC Micro where anything could be replaced so easily and all you need is a scope to dx any issues.

Today everything is a board swap. When I started repairing CTs and MRIs back in the 90s, with other medical equipment, you could actually troubleshoot and replace components. Now, board swaps.