For the last few weeks I've been tinkering with an LC II I picked up as part of a large lot.
I thought out of all the systems this one was going to be a simple recap but after the recap its still dead. Powers up to a black screen, there is a sync signal there, but no chime.
Everything around the area of the old caps has been well cleaned and reflowed. I cannot see any damaged traces etc. The outputs on the PSU all measure fine.
Looking over it with my logic probe there is activity on the RAM and the clocks seem fine (certainly pulsing although I haven't read frequency). There is nothing though on the databus, well nothing other than a quick pulse just after power on. The CPU isn't halted so its almost as if the system tries to read out of ROM and falls at the first hurdle.
Are the roms on these things a weak point or are there any other known weak points of the LC II.
If I wanted to write myself a new set of ROMs would anyone have a guide for how to do it? I've got an eeprom writer but each time I go looking for the ROM image online its a single 512k file. Thing is I need the 4x 128 images for my LC II. Alternatively does anyone know if the TL866 eeprom reader/programmer can read out the original ROMs? If I could even look at them it might give me some idea as to if they are good or bad. I just don't see an option for the toshiba rom in the TL866 software.
Battery installed? This is one of the Macs that won't work otherwise. Install a battery, power it on, let it sit for some minutes, turn it off and back on. Should come to life then.
I have about 8 Mac LC's. I only received one I couldnt save. They are severely problem prone in two ways. First is the Surface Mount capacitors ALL LEAK and they severely corrode the board. The best way to tackle this is remove any Clock battery if it still has one. Remove the RAM and VRAM modules and any PD card if it has one and wash it in the dish washer with auto dishwasher detergent. This will remove the caustic leakage from the capacitors. DO NOT ALLOW IT TO DRY in the dishwasher. Let it air dry a couple days on its own in a warm dry place. Direct sunlight works best.
Second issue is the PSU. Its a tight little unit and it gets hot in there. Some of the through hole caps leak pretty badly and might even damage some traced. I have a post on recapping the LC psu: https://www.vcfed.org/forum/forum/te...pacitor-values
Open the psu and smell and look for leakage. If none is found you can try powering the board back up after a wash. IT may run but that is only a temporary fix as the electrolyte was washed away from the board. THE BOARD WILL NEED A RECAP. The PSU may need one.
I have repaired the LC, LC II, and LC III, never seen the LC III plus but im sure its similar.
Battery installed? This is one of the Macs that won't work otherwise. Install a battery, power it on, let it sit for some minutes, turn it off and back on. Should come to life then.
I have never has an issue powering any LC without a battery. Its best to leave the battery out. I have an original LC on my bench now, but if you want me to test this I can go get an LC II and try it out.
I've recapped multiple systems in my time and this one got the same treatment, 1 pad did come off on me but I fixed it with a bit of wire, I've again checked and this bodge is good. If it interests you, you can see some of my initial efforts (the recap mostly) over on youtube - https://youtu.be/RHTJZtNHN04
I have tried it with a battery and it makes no difference either way. There are no memory modules installed at present only the onboard RAM. I've tried it both with the VRAM modules installed and left out, same result. One thing I thought was maybe the 2 bus transceivers but those too have been swapped and no change. I suppose it could still be corrosion under one of the large ICs but the leakage while bad wasn't terrible, I've seen a lot worse. One thing I don't have is a dishwaser (we're actually looking to get a new kitchen soon and this will be added) but I may give the board a wash in the sink and see if it helps. Last time I did this with a board I washed it, then rinsed down with alcohol and let it drip dry, nothing to loose in trying it I suppose, the board doesn't work anyway.
The outputs of the PSU look fine on my meter and looking inside there is no evidence of leaking caps. I might just swap out those caps and see if it makes a difference but I suspect not.
I will check out your video when you have time. This sounds Similar to the LC original I could not revive. It has so much leakage Im pretty sure the solder bridges between the IC's and the board were not making a connection anymore and it would require the ICs and SMD TTL chips to be removed cleaned and resoldered back on. I would check the legs of the smd chips to the nearest via and check for continuity. Dont wory abut the Chime (also does your LC II use the original speaker fan bracket with four finders [they may need cleaning] or does it connect fan and speaker directly to board with headers? Macs are notorious for very quiet to no sound when caps are not working right. You are using a Mac monitor or an adapter set to the sub-vga levels?
Funny you should say that as the legs on the processor were horribly green. I have reflowed all of this and they look better although to treat it properly the chip would need to come off. I'm not the worst at soldering (not the best either by a long means) but that 030 has a very fine pitch and I'm not sure I want to try completely removing it.
My LCII has the speaker and fan that connect with individual headers.
I've tried both a mac monitor and a cable I made up for my Performa. The cable to my LCD monitor is handier, just because of desk space but I'll hook up the CRT again later and have another look. Last time though on he CRT is was just the same black screen. One thing to note is that the LCD shows an initial white flash then black screen but I can't be sure if its the MAC causing the flash or just the monitor getting the sync signal.
Your right, they probably need to come out completely to do a better job of cleaning but the dishwasher will get any cap residue under the chip (I lay the boards facing down in the wash cycle). If you want to try this., get a jar of flux and coat one side of a square IC with flux paste and melt some solder over all the pins to mix up and clean the legs from older solder. You can use braid or a pulling wicking motion and some copper wool to clean off the excess. Clean with isopropyl alcohol then test the legs for shorts you can see. Then move to the other side. Its long an drawn out but it may help. I bought magnification goggles for this type of work.
Mick
Truth be told this is making me think about that LC I couldn't fix. I think I still have the board. I should give it another crack. I know the ROM's are all good. That board has terrible leakage and ever leg was just.... filthy.
Gave the board a really good wash, let it dry for 48 hours and gave it another clean this evening with IPA but no difference in behaviour. Black screen, no chime and no activity on the databus. The only thing I can think now is the ROMs but since I don't have another set there is nothing further I can do. For now the system has been put back together and will be put into storage. maybe one day I'll get another LC II and can revisit this but for now... Its dead Jim.
