Brett's STE - Repair thread

[stephen_usher]

Surely you only get gremlins if you feed them after midnight?

[rubber_jonnie]

Surely you only get gremlins if you feed them after midnight?

Maybe that was why it still wasn't working

Or did I mean pixels....

I'm so confused....

[rubber_jonnie]

I'm feeling like a minor celebration. I traced A1 and found that it should be connected to pin 2 of the DMA. Only it wasn't, so I hooked it up and I now get this:

Would be interesting (and possibly educational) to know where exactly the track broke. Have you narrowed that down yet?

Ok, so the track is good along the bottom of the board from the DMA. It is then good through the via to the top of the board. Where it comes out is shown by the red circle.

DMA_Track_A1.jpg (422.13 KiB) Viewed 1272 times

The red arrow indicates a spot just before the ROM sockets where I removed the solder mask in order to buzz it out, and it is good up to that point. The damage is therefore likely to be the trace that was originally damaged at the ROM socket, so pin 12 of the HI ROM socket.

[Badwolf]

Great progress!

I had a similar output the other day that turned out to be a couple of shorted address lines.

Clearly some work left to be done, but the little red led on my diag cart which shows ROM access is now flickering, a good indicator that ROM access is at least being tried. It was completely dead up until now.

Don't forget the diag cart also talks over serial!

BW

[rubber_jonnie]

Great progress!

I had a similar output the other day that turned out to be a couple of shorted address lines.

Clearly some work left to be done, but the little red led on my diag cart which shows ROM access is now flickering, a good indicator that ROM access is at least being tried. It was completely dead up until now.

Don't forget the diag cart also talks over serial!

BW

Yep, going to hook up to my HP Jornada over serial later, see if it gives me anything

[stephen_usher]

I'm waiting for the next episode... Did you get any time to look at the machine last night?

[rubber_jonnie]

I'm waiting for the next episode... Did you get any time to look at the machine last night?

Sadly no time yesterday, and today is unlikely too, we've had some family stuff going on that has been a bit of a diversion, so my repair time has been limited.

I did try both diag carts, but still nothing. I need to hook up my 2nd bench PSU before I try the serial port though as I think the serial ICs need 12v. I'll see if I can at least do that. I had done it initially but got nothing.

[stephen_usher]

Fair enough. I hope that the family stuff gets sorted soon.

[rubber_jonnie]

Fair enough. I hope that the family stuff gets sorted soon.

Cheers, me too!

[exxos]

Just a thought.. When you say your limiting the amps, do you mean you have the psu set to limit at say 2.5amps, or have you limited the amps the STE is trying to pull ?

It is dependent on voltage and other things, but a machine doesn't always pull the same amount as another. So if the machine is trying to pull 2 Amps, and your limiting to 1.8amps, then it will add to your troubles.