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IIci Cache Card Failures
Posted by: Phipli on 2022-10-29 01:24:50 Folks, Back in the early 2000s or so, my family had some IIci cache cards that failed somehow and would cause a sadmac when the computer tried to boot. Being from a family that isn't great at throwing things out (we're quite good at fixing things, even if it takes 20 years to get around to it - yes I do feel shame), I have two of these cards on hand. Was there a known common failure mode for these cards? I anticipate it wasn't electrolytics leaking given the time and that it would have been visible. I removed them yesterday as they were starting to leak. None of the ceramics look like they exploded and I can't see evidence of hot spots on the SRAM chips. How reliable was the SRAM? I haven't done more than a visual inspection so far as I've only just got hold of them, I'll compare the resistance to ground and Vcc on each chip on both boards to see if part of a chip is shorted. I already checked for shorted caps. Hopefully I can make at least one good cache board out of the two.
Posted by: mg.man on 2022-10-29 01:50:37 Sorry if an obvious question... but have you tried them with the capacitors (C10, C22) in place? - https://oldcrap.org/2019/09/22/macintosh-iici/#jp-carousel-5482
Posted by: LetraStudio on 2022-10-29 02:17:45 Edit : Whoops - replied from my tablet to confuse things. I removed the capacitors yesterday, about 20 years after the cards failed 🤣 I picked that photo to stop people telling me to remove the caps! Don't worry about obvious questions, obvious questions lead to obvious solutions, which are the best kind.
Posted by: mg.man on 2022-10-29 02:24:27 obvious questions lead to obvious solutions 🙂 ...sorry that was not the case this time. 😉 That said... another obvious question... have you tried them with 'new' caps? The IIci launched in 1989, so even by 'early 2000s' the cache card would have been ~>15 years old. If it / they had led a hard life, it's not inconceivable that those caps may have failed? 🤔 Just trying to eliminate the simple possibilities.
Posted by: Phipli on 2022-10-29 02:32:42 🙂 ...sorry that was not the case this time. 😉 That said... another obvious question... have you tried them with 'new' caps? The IIci launched in 1989, so even by 'early 2000s' the cache card would have been ~>15 years old. If it / they had led a hard life, it's not inconceivable that those caps may have failed? 🤔 Just trying to eliminate the simple possibilities. The caps were rated at 25v and 35v in the two boards and both are dated 1991, plus we're talking more 10 years than 15. It isn't inconceivable - I mean, something failed, and I will test at some point, but I don't have a machine to test in and the caps only arrived this morning. Basically I guess I'm asking if there was another common failure mode, as I'm in the process of recapping anyway, just to preserve the PCBs. This is the literature review before the investigation.
Posted by: MrFahrenheit on 2022-10-29 05:30:52 The caps were rated at 25v and 35v in the two boards and both are dated 1991, plus we're talking more 10 years than 15. It isn't inconceivable - I mean, something failed, and I will test at some point, but I don't have a machine to test in and the caps only arrived this morning. Basically I guess I'm asking if there was another common failure mode, as I'm in the process of recapping anyway, just to preserve the PCBs. This is the literature review before the investigation. I’ve seen these cache cards and Apple IIe cards both use either 25v or 35v caps, and I always just replace with 35v. But I have not yet seen one of these cache cards sad Mac. I have many.
Posted by: imactheknife on 2022-10-29 08:52:20 Both mine work. Replaced with 35v caps
Posted by: beachycove on 2022-10-29 10:07:19 As I recall, the fellow who developed TenFourFox had IIci cache cards fail regularly in a machine used as a server of some sort running 24/7. I think they may well be prone to failure, but if it turned out just to be two caps, well, that would be a good thing.
Posted by: beachycove on 2022-10-29 10:08:05 Cameron Kaiser. His name leapt to mind just as I pressed the post button.
Posted by: joshc on 2022-10-29 11:42:21 I had a bad one of these too, bad SRAM I think.
Posted by: Phipli on 2022-10-29 12:42:03 As I recall, the fellow who developed TenFourFox had IIci cache cards fail regularly in a machine used as a server of some sort running 24/7. I think they may well be prone to failure, but if it turned out just to be two caps, well, that would be a good thing. When the one I was using it was a daily driver, 7 days a week, all year, they might not like the hours adding up. If it was under reasonable useage in its life before me it might have done several hours work on most days for over 10 years. I had a bad one of these too, bad SRAM I think. As we lost two I was assuming it was more common. I was expecting everyone to be saying they lost one. Guess sometimes you can be just unlucky.
Posted by: geokov on 2024-01-24 15:35:51 Hello, a quick question for this thread. Did you replace the caps on your cache cards with electrolytic or tantalum caps? I was recently given two IIci cache cards for my IIci project and neither one works. I'd like to replace the caps on the cache cards to start but I'm not sure what to use as replacements? If possible, could you give me link to what you used? Thanks
Posted by: Phipli on 2024-01-24 15:48:03 Hello, a quick question for this thread. Did you replace the caps on your cache cards with electrolytic or tantalum caps? I was recently given two IIci cache cards for my IIci project and neither one works. I'd like to replace the caps on the cache cards to start but I'm not sure what to use as replacements? If possible, could you give me link to what you used? Thanks I used tantalums. I don't have a record of what they were, specifically, but match the capacitance and use parts that are 25v rated.
Posted by: geokov on 2024-01-24 19:47:37 Thank you, I go for tantalums as well.
Posted by: trag on 2024-02-02 15:37:45 I used tantalums. I don't have a record of what they were, specifically, but match the capacitance and use parts that are 25v rated. IIRC, on the IIci cache card they are 22 uF. But one should double check, as my memory is old and corroded.
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