Apple IIc Plus won't boot - help?

[spacecadet]

So quite a while ago now one of the good guys on this forum gave me an Apple IIc Plus that he told me wasn't working but I thought it would be worth trying to fix. I'm finally getting around to it now that I'm stuck at home for a while and I just tried to boot it up today to see what it does, and lo and behold it is doing exactly what his original note pasted to the machine says it does.

 

It starts trying to boot but once it gets to the point where it would normally drop you into BASIC (assuming no disk in the drive; I don't have a bootable Apple 8 bit 3.5" disk), it instead just prints and endless stream of flashing "L"s on the screen.

 

I ran the self diagnostic and it gets to the end and just says "ROM". (It also has the usual gibberish elsewhere on the screen, but I understand that that's normal even when it says "System OK".)

 

I did open the machine up and the board itself is in really good shape, as is the whole computer. There's nothing obvious that's blown on the board, leaking or anything like that. I do remember that the previous owner said he had tried reseating all the socketed chips already, but never went further than that.

 

I'm not averse to trying to diagnose every chip on the board but I thought I'd just ask here in case anyone else has seen this and definitively knows what it is. I did a Google search for these symptoms and didn't come up with anything. Would assuming it is the actual ROM chip and replacing that be a bad place to start? ReactiveMicro seems to sell some upgraded ROM chips for pretty cheap: https://www.reactivemicro.com/product/firmware-rom/

 

I was thinking to start there in the absence of any other info, but if anyone here knows any different, I'd love to know if you've got other ideas.

 

 

Edited April 15, 2020 by spacecadet

[GameGeezer]

8 hours ago, spacecadet said:

So quite a while ago now one of the good guys on this forum gave me an Apple IIc Plus that he told me wasn't working but I thought it would be worth trying to fix. I'm finally getting around to it now that I'm stuck at home for a while and I just tried to boot it up today to see what it does, and lo and behold it is doing exactly what his original note pasted to the machine says it does.

 

It starts trying to boot but once it gets to the point where it would normally drop you into BASIC (assuming no disk in the drive; I don't have a bootable Apple 8 bit 3.5" disk), it instead just prints and endless stream of flashing "L"s on the screen.

 

I ran the self diagnostic and it gets to the end and just says "ROM". (It also has the usual gibberish elsewhere on the screen, but I understand that that's normal even when it says "System OK".)

 

I did open the machine up and the board itself is in really good shape, as is the whole computer. There's nothing obvious that's blown on the board, leaking or anything like that. I do remember that the previous owner said he had tried reseating all the socketed chips already, but never went further than that.

 

I'm not averse to trying to diagnose every chip on the board but I thought I'd just ask here in case anyone else has seen this and definitively knows what it is. I did a Google search for these symptoms and didn't come up with anything. Would assuming it is the actual ROM chip and replacing that be a bad place to start? ReactiveMicro seems to sell some upgraded ROM chips for pretty cheap: https://www.reactivemicro.com/product/firmware-rom/

 

I was thinking to start there in the absence of any other info, but if anyone here knows any different, I'd love to know if you've got other ideas.

 

 

 

I'd say this is probably bad SRAM. 

 

Did you have a keyboard connected during the power-on tests? I recall that the //c+ could be picky about that. 

 

Try repeating the power-on with a KB attached, and the ESC key held. Try a normal //c KB if you have one, too. 

 

The SRAM and the Char Gen would come next. Those are soldered (and heat-sensitive), so use a hot air station and vac pump to remove them. In fact, if you have hot air, gently reflow the board first. It could be a cold joint. 

 

If you reach a point where you give up hope, my //c+ has some damage (original KB is bad, and top case is cracked/warped). Should you be unable to fix it, I'd trade for spares. 

[spacecadet]

I did try it with a keyboard attached. I don't even know how to do the self-test without a keyboard attached.

 

Wouldn't a bad SRAM chip say something different in the self test? What I've read suggests it would say "RAM" and then a number that corresponds with the chip.