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MAC LC

Gary C

Gary C

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Joined
May 26, 2018
Messages
2,587
Location
Lancashire, UK
Had a mac LC sat in the garage for a few months now that would not work.

PSU had failed but a really cheap one turned up, so rather than fix I replaced (but will fix the spare at some point)

Powered up and no bong :(

Replaced all the caps, which while I don't normally agree with 'recapping' without reason, with these it seems to be a necessary step to do by rote.

PRAM battery is good and tried several key combos but no sound. Poking about, first thing to check is if the ROM is being accessed and yes, there is activity on all lines. Next to check if the video chip is being addressed. The CULTDAC itself is producing sync pulses and the VRAM data bus is active, RW is pulsing and all data bus lines active, however address line A0 has no activity at all. Line comes from a via about 3" away where there is activity, but nothing at pin 17. The trace on the board looks perfect, no corrosion or visible defects, but no continuity between the via and pin 17.

Sucked the via clean and soldered some wirewrap into it then run to pin 17 on the DAC, and its working !

No idea why it doesn't bong yet but it boots cleanly from the HD so thats good.
 
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Well first off those psus always need a recap.. secondly the onboard caps are first gen smd and should all be replaced. I agree with you on not recapping for the sake of recapling but any late 80s early 90s mac with smd caps will definitely require them be removed. If its an LC 1 i have seen them have soo much leakage the board needed a throrough wash to get off all the electrolyte. You may want to make sure if its got the 4 rom sockets that the so kets and pins are clean. You dont need a battery to start the system . I have 5 or 6 pizza box stule mac LCs. They are my favorite macintosh. It has a vram module? Wont work without it. Does this LC have a speaker that plugs in via headers or have the fan/speaker bracket whichmakes contact by preasure on contacts? That may be why no bong.
 
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Is your PSU a TDK or Astec unit? The Astecs are hit or miss like any 30 year old PSU but the TDKs all go bad due to using ELNA LongLife caps inside which ALWAYS leak, and badly.

I'm pretty sure all the original LCs use the less reliable speaker connection via contact pads (no wire header) so that's something to check. Try the headphone output if you haven't already.
 
3lectr1c said:
I'm pretty sure all the original LCs use the less reliable speaker connection via contact pads (no wire header) so that's something to check. Try the headphone output if you haven't already.
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I have seen an original LC which used a pin header for the speaker. Maybe the last run of them..
 
I don't doubt that. Keeping track of Apple's many production changes can be...a nightmare. Just look at all the LC475 variants (different model numbers aside, they shipped in 3 different case variants...)
 
I know the LC's get alot of crap.. But they are still my favorite mac. Especially the LC original. I would take one of these any day of the week over the horribly built compact macs... They were the first macintosh a real person could afford and they were in the schools so the first mac most people used. And with that APPLE II card they were a bridge between old and new. Great with BlueSCSI (because you cant get SCSI2SD anymore) and an external SCSI cdrom. Add 512K VRAM and a Hi res RGB monitor and you have a pretty nice early 90s box.
 
I've got an LC III and it's a pretty nice system. I don't really hear anyone giving them crap - just the first two sometimes because they're rather slow and somewhat handicapped. Most still agree they're great systems though. Very easy to work on.
 
3lectr1c said:
just the first two sometimes because they're rather slow and somewhat handicapped.
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That is what I mean.. When they are still leagues better than the compact mac.. And color.

I have an LCIII as well. The sound chip comes and goes. I have to rework it with heat for it to work again since you cannot find the chip.
 
The SE/30 has them beat in performance and also expandability in many ways, I completely understand why they're as loved as they are. The original SE is also pretty darn reliable, and the SE/30 would be too if it wasn't for bad logic board caps.
I am of the general opinion that all the Macs have their own merits and fans. I get not liking them though, the B&W screens are limiting. I will add though that Bolle on 68kMLA has reverse engineered a very rare card for the SE/30 that adds internal grayscale video, he's made a few but I think it's gonna be a bit before they're up for general sale. That does definitely add some usability. An LC will always be cheaper than that of course, people just love the original form-factor.
 
Well, the bong was missing because I had removed the speaker socket to get at one of the caps during replacement and had forgotten to put it back in.

But this morning, failed to boot. Looking at the address bus, the voltages were ~1.5V but with some pressing about, this would move between 0.8 & 2.5V. Odd

Wiping around the ECIT improved the voltage, so thought it would be down to cap goo even though there was none visible. Gave the board a good wash in the sink with some fairy liquid, dried off with my SMD rework station (which has proved to have dozens of uses, just not on SMD's yet) and now it works fine.

Pulled out the 12" RGB display that had too much brightness and gave that a tweak and now its a nice complete machine.

Wont format a disk yet though.
 
Those auto-inject floppy drives suck in dust like crazy. Probably just needs a good clean and relube, and possibly also a replacement eject motor gear. There's one in those that usually crumbles with age.
 
Good point.

Quick strip down and all gears are fine and surprisingly well lubricated. The carriage was a bit stiff but thats now sorted. The stop switch was malfunctioning causing the eject gear to continually rotate but thats ok now too.

Head steps fine and are nice and clean but its possible the floppy is a duffer and only have one to hand.

Its a faster machine than I expected and it has a few programs installed including Lemmings but it needs the manual to get past the copy protection. Still a shame about that 16 bit databus.
 
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Ho hum. Lemmings is a cracked version, just press return and it runs.

Floppy, decided to plug the drive into the second port and format ran fine. Plugged it back into the original socket and it works there too !

Might just be dirty connector but will check the joints on the connector
 
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