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Thanks Corey. I had posted something similar 3 years ago on the Lisalist forum. I used an OPL560 IR sensor which did the trick. Recently, I also had a similar problem with the track zero interrupt sensor of an ST-506 disk drive in a 5MB Profile. See here. In that case, the IR emitter was...

Thanks Brooklyn. I usually don't check resistors that do not look burnt, but becoming desperate, I did. One of the resistors feeding TDA1170 (R28) showed 470 kOhms when it should be only 56k. After a quick replacement, I got the problem fixed. R28 is actually next to C18 on the board which I...

Hello my fellow Lisa geeks ! Can someone help me diagnose this video problem ? The video board was originally OK-ish, but with some jumpy behavior. So I went on to change all 10uF e-caps (2x100V and 3x16V) which has always worked for me. But then I got this screen below. Tweaking all pots does...

I've had instances where the optocoupler was OK, but the connections to the LB was faulty. You might want to reflux some of these pins and see what happens.

Thanks everyone. I think that's all the info I needed. Will take the bull by the horn and hopefully acquire this new PCB rework skill :). I will report back

@LaPorta: thanks. This also makes a lot of sense as the inner ground plane is a major heat sink that forces more heat into the chip and away from the pins. Some suggest to stick a heat sink on top of the SMD chip to lower the temperature. Looks a bit cumbersome to do, but it makes sense too...

Thanks @obsolete. I just ordered some. This low-T route makes a lot of sense to me. I'll try with a round nozzle, and report back

Thanks ! Has anyone tried a low temperature solder alloy like QuikChip ?

Sorry to bump this, but I could really benefit from a good advice. I read that hot-air de-soldering an SMD chip can fry that chip, with temperatures up to 400C. So removing the defective SWIM is not the problem. Re-soldering a donor SWIM is not a problem either. But how can you de-solder the new...

Update: the SWIM hypothesis is getting some traction. Thinking that by some kind of miracle there was a bad solder joint on the SWIM chip, I went ahead and hot-aired the perimeter of the chip. While it was still warm, I tried to boot, and this time, I could not get the chime/boot, and the screen...

Well I figured that there are Friday the 13th every 7th month. And there must be multiple flight 13s running on these days (one per airline ?), each with multiple seats on row 13. So it was rare for me, but nothing too peculiar.....

Completely off topic, and I apologize for that. But this reminds of one day that I was on a commercial flight. It was Friday the 13th, flight number 13, and I was seated in row 13.

It does not matter whether I connect the FDD and HDD with the internal vs external connectors. I get the same effect. I spent the morning following the VSNS and RESET signals on the LB. I did not realize that the reset switch changes the VSNS from 5V to ~3.9V, with brings RESET from HI to LO...

Thanks. Yes, the SWIM chip came to mind, but I'd hate to replace it if it's not the culprit. Would that explain all the symptoms I see ? I fail to see how it would affect the reset and HDD issues. PS: I'll keep you in mind when my SE30 dust settles

After so many years, I decided to go through a pile (dozen) of SE-30 logic boards that I had bought on CL. I meticulously recap them one by one, and some of them work, but others don't. This particular one gives me the following symptoms: 1) Booth chime is OK. Video is good 2) When no FDD or...

Thanks. I have sent him a message

This was also my suspicion until I went through the whole forensics analysis that I described. Do any of your 5MB show a SN starting with a D, with a large font and printed vs glued on ? I just could not find one. Must be ! I looked everywhere I could 😊

I recently realized that among my four Profile HDDs, one of them is actually the 10MB model (from looking at the controller and the HDD), even though the model number was A9M0005. See pic below This spurred me to look into model and serial numbers. First of, my other three "true" 5MB show...

I think I found the problem/solution. The issue is that the jumper configuration from stason.org is wrong. The jumper bank at the front of the HDD has 7 positions. stason.org has from left to right (HDD upside down, see pic below): SCSI ID0, 1 and 2, then blank, motor spin-up, reserved, LED out...

Funny I'm having the same problem again, this time with a Mac IIci. And I forgot whether the passthrough terminator worked :(. I'll take a look at my Color Classic and check. Any luck with your LC III @reodraca ?