LC II no chime, grey screen, some activity on the address and data bus

[Phipli]

The first three are spaced 512 apart (the next isn't.

First thing I'd try is reseating it in the reader and seeing if you get the same again. It might have just been a bad connection on an address line.

 

[funnymike]

I tried again (10 times), with the same result. Could it be a different Apple Rom? But it is highly unlikely that all differences are on one chip only.

 

[Phipli]

I tried again (10 times), with the same result. Could it be a different Apple Rom? But it is highly unlikely that all differences are on one chip only.

Do you have an EPROM to flash the correct one on to? It is certainly likely that it will fix it! Give it a go.

 

[bigmessowires]

You mentioned earlier that you put the suspicious ROM into another LCII and it showed the same symptoms there. Did you try taking the ROM from that other LCII and putting it into the first one?

 

[funnymike]

You mentioned earlier that you put the suspicious ROM into another LCII and it showed the same symptoms there. Did you try taking the ROM from that other LCII and putting it into the first one?

I didn't dare to do that, since i didn't want to damage the "good" roms with a potentially damaged (because recapped) mainboard.

However, i think I will follow Phipli's suggestion and spend few bucks for some eeproms. I will keep you updated!

 

[bigmessowires]

However, i think I will follow Phipli's suggestion and spend few bucks for some eeproms. I will keep you updated!

I have an EEPROM programmer, and a 29F010B that I don't have any use for. If the LCII ROMs are indeed 27C010 then 29F010B should be a drop-in replacement. Since @jajan547 was kind enough to send me a missing SE/30 part for the cost of postage, I will pay it forward and make you the same offer. Just send me the ROM file that you want programmed to the chip.

 

[funnymike]

I have an EEPROM programmer, and a 29F010B that I don't have any use for. If the LCII ROMs are indeed 27C010 then 29F010B should be a drop-in replacement. Since @jajan547 was kind enough to send me a missing SE/30 part for the cost of postage, I will pay it forward and make you the same offer. Just send me the ROM file that you want programmed to the chip.

Wow! Thank so much for this gentle offer! The people here in this forum are so nice and always willing to help! But I live in Germany and most likely its not worth shipping the eeproms from the US to here. I suspect that I can find some cheap chips here as well! But thanks again!

 

[funnymike]

A brief update: I finally got the machine up running again, by replacing the 341-0476 rom chip that contained the errors with an intel 27C010. Incredible to see that LCII motherboard working again after leaking caps and bad rom chips. Thanks so much for all of your kind help.

 

[David Cook]

Well, well, well. I don't know what's up with LC II computers and bad 341-0476 ROMs. I had the same symptoms: no chime, grey screen, good voltages, oscillators good, ~reset and ROM OE good.

I played switch-a-roo with another LC II and found the ROM was bad. I burned a replacement with the attached file and a Macronix MX27C1000DC-90.



This got the machine working. However, there was an unrelated problem where a bad chime would occur when adding RAM (SIMMs).

The root cause was a corroded trace (for pin 23) underneath the SIMM socket near capacitor C2. You can see dull vias and lightly corroded traces nearby. I found the bad one by toning out each SIMM pin against the schematic.



The fix is a wire underneath the board going from pin 23 of the SIMM socket to a trace that leads to the same line on the VRAM. (I suspect this is the exact same path taken on the front side of the board underneath the socket.)



- David