exxos's Atari, Amiga & retro forum

I always just look for dodgy looking data on the data line. That's the first one. Of course this doesn't help with addressing faults but weird data line pulses is my first test. I hope your toy 'scope is good enough for that!

stephen_usher wrote: ↑Fri Jun 11, 2021 4:24 pm I always just look for dodgy looking data on the data line. That's the first one. Of course this doesn't help with addressing faults but weird data line pulses is my first test. I hope your toy 'scope is good enough for that!

We'll find out I guess!!

Fisher Price awaaaaaay

@stephen_usher Good call, I just checked and IC4 has nothing on data out, 5, 6 & 7 are all showing signs of life.

We'll go with that one first.

From my experience most common faults on electron

• not connected keyboard.
• ula socket (if you have one - replacement was available from Bulgarian demobile )
• ram

You need pretty very bad luck to have ula damaged.

Sometimes piggybacking ram can help you find which one is damaged, but never worked for me. Personally I would replace all chips, but that's me.

arkadiusz.makarenko wrote: ↑Sat Jun 12, 2021 9:24 am From my experience most common faults on electron

• not connected keyboard.
• ula socket (if you have one - replacement was available from Bulgarian demobile )
• ram

You need pretty very bad luck to have ula damaged.

Sometimes piggybacking ram can help you find which one is damaged, but never worked for me. Personally I would replace all chips, but that's me.

Yeah, it seems like a BBC with respect to the keyboard needing to be plugged in, though in this case it makes no difference. Having had a keyboard fault with my BBC B I did think this might be a possibility.

I have buzzed out all the switches which all worked, and the ribbon, despite obvious corrosion, has good continuity and no shorts between wires. If it fails later I'll just make a replacement.

As for the ULA, it's a glop top and directly soldered in, so I can guarantee that the socket isn't a problem!

Replacement RAM is in the post, so I'll do the prep whilst I'm waiting and fit a socket. Due to my limited workshop at the moment, I will just do the RAM IC that has no D Out activity, unless of course that doesn't fix it, then I will review.

I've not had any luck with piggybacking myself, but I know it can sometimes help.

Ok, IC4 is gone and has a socket in it's place, just have to wait for the RAM to arrive so I can test.

Well, you could power on and see if the fault has changed without the chip in there.

stephen_usher wrote: ↑Sat Jun 12, 2021 12:14 pm Well, you could power on and see if the fault has changed without the chip in there.

I will later on, but first, lunch

stephen_usher wrote: ↑Sat Jun 12, 2021 12:14 pm Well, you could power on and see if the fault has changed without the chip in there.

Problem is identical with the RAM chip gone, at least I didn't make it any worse

That, to me at least, suggests that chip was bad anyway, just have to wait for the new ICs now.

Yeah. It's always good to check. Maybe check what signals the RAM chip is getting from the ULA whilst you have the socket there and maybe buzz out the data path to the ULA. (Being paranoid.)