New Zealand Vintage Computer Forums

Hi guys,

I bought a 2c on trademe recently and it's a little dodgy (as seen below).
Any thoughts?

Doesn,'t look too good. I think the IIc has a self test diagnostic routine like the IIe.

Try pressing the keys Ctrl- Open Apple - Closed Apple - Reset all at the same time and see what happens. You should get a series of flashing colour blocks as it sequences through the ICs...if one is faulty it will list it.

If absolutely nothing happens it might be a more fundamental problem. Like the processor itself.

Does nothing. But I see a a cursor flying through the screen, which makes me think a ram check is running. I had a look a the ROMS and they all seemed to read fine.
I'm thinking either DRAM or something to do with the logic to decode to it.

Well, DRAM and associate logic chips certainly do fail. The logic chips supporting memory are the biggest pain the arse to track down in a diagnostic sense.

Just some suggestions which may or may not work.

- If you have or can find a spare DRAM chip, try the old piggyback method (I'm assuming you know what I mean by this?). It doesn't work for all DRAM problems but I've found three occasions where it's worked for me.

- Short circuited DRAM chips get very (very!) hot. A simple touch test will verify if this is the case.

- Sometimes electrolytic capacitors can leak electrolyte out onto the circuit board causing a short. Check for this...it will be an area of dullness under the cap. I managed to resurrect a Mac Classic II which had this problem by washing the board in a dishwasher! Only recommeded as a last resort though.

Otherwise, it's probably out with the logic probe and a circuit diagram to see if you can trace what's happening to the signals starting with the CPU.

Are the chips socketed at all?

Tez

Main chips are, CPU, IOU, MMU, Roms. Unfortunatly not ram. But on the plus side, this is the model with only 4 dram chips
The condition of the socketed chips seems to be a bit poor, with mild rust on them, but i removed and cleaned them with no effect. It does sound like a concerted effort with the logic probe is in order.

Yes. If you have socketed equivalent RAM chips from other units in your collection it would certainly be worth the piggyback test.

Anyway, let us know how you get on. I enjoy reading about people's diagnosis and repair experiences. Anyone else reading this have any ideas?

When I'm stuck I often take my thoughts to the (international) Vintage computer forums. There is an Early Apple forum there, and helpful people who are complete gurus when it comes to these machines.

Good luck!

Well wouldn't you know it, the lcd screen i got with the 2c is also broken. It's a very dark black colour and requires some serious light to see any of the characters. That's a real shame as I think they are pretty rare screens.

Sorry to hear that Matt, espcially considering you paid quite a bit for it.

I see you've posted a note of VCF. Looks like others feel it's a RAM issue too. How easy are those RAM chips to get?

4464 64k x 4bit DRAMs are easy to get... in the U.S.
They are in Amigas and I suspect lots of other machines.
To get them here I'm not sure where I'd start.

I just picked up a bunch of I.C. sockets tonight anyway, so I'll desolder them all and try swapping the DRAM around.
I was feeling for hot chips yesterday, and a chip labelled GLU is fairly warm compared to the others, so maybe that is the problem.

I'm a bit peaved about the LCD though, not so much because of the money, just because it's rare and it's gone now.
Unless I find someone with busted LCD electronics and a good screen it doesn't have much use now.

This auction gets even better. I have the same problem as you, my video IC doesn't match the monitor so everything is offset vertically.

matsondawson wrote:Well wouldn't you know it, the lcd screen i got with the 2c is also broken. It's a very dark black colour and requires some serious light to see any of the characters. That's a real shame as I think they are pretty rare screens.

I read somewhere someone described these as beyond rare, someone else saying he'd estimated there might be less than 100 out there surviving, and of course if you can compare Apples with umm, Atari's, there's always those rare cart finds where they sell for five figures, for titles which supposedly have the same kind of number in ownership.

There was another person who said he'd had a broken/failed IIc LCD screen and was looking for one. You might be able to obtain that one. Sorry no links, but all probably googleable.

YetiSeti wrote:

matsondawson wrote:Well wouldn't you know it, the lcd screen i got with the 2c is also broken. It's a very dark black colour and requires some serious light to see any of the characters. That's a real shame as I think they are pretty rare screens.

I read somewhere someone described these as beyond rare, someone else saying he'd estimated there might be less than 100 out there surviving, and of course if you can compare Apples with umm, Atari's, there's always those rare cart finds where they sell for five figures, for titles which supposedly have the same kind of number in ownership.

That is quite possibly true - the LCD for the //c was a bit of a failure as I remember it, largely because the unit itself was so bad. Of course I havent seen the panel in question, but they were always notoriously dark (almost to the point of unreadable) - from new. No back lighting or anything fancy like that - so theres a chance that its actually functioning as designed....maybe

Ok, I've figured out the issue. I picked up another 2c off trade me for $40 and swapped a bunch of chips. It turns out to be the CPU.
I did try another CPU, must have been broken too.
Anyone got a spare 6502a?

Those CPUs do give up the ghost from time to time. My Apple clone (Redstone) wouldn't work a few months ago. The reason? A broken CPU. Unfortunately I've used my only spare to repair that one. The spare was salvaged from a parts-only Vic 20.

matsondawson wrote:Well wouldn't you know it, the lcd screen i got with the 2c is also broken. It's a very dark black colour and requires some serious light to see any of the characters. That's a real shame as I think they are pretty rare screens.

Sounds like a failed backlight... I guess it would be possible to replace the backlight with something else of a similar size?