68kMLA Classic Interface

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Dead Macintosh IIsi
Posted by: cafarmer on 2023-06-18 10:10:28
The other day, I went to turn on my Mac IIsi and it would not turn on; no click, no noise…nothing. I had turned it on just hours before that and most days it is on at some point. I bought a recap kit and recapped the PSU (already recapped the motherboard a year or so ago). But still nothing - dead silence when I push the button. Battery tested good and fuses have continuity. I also tried the keyboard power button - nothing. Still hoping the problem is the PSU, but I have my doubts. Any ideas would be welcome.
Posted by: Phipli on 2023-06-18 10:19:24
There are multiple ATX adapters available if you decide to replace the guts with something else. For example :

IIci etc. ATX to 10pin Adapter

A friend designed an adapter for converting ATX to connect to a IIcx, IIci, IIsi, Q700, C/Q650, IIvx, IIvi, P600, Q800 and 7100. Handy for bench testing, and with a little work on mounting, may help with replacing PSUs. He has shared the design. You're free to make some for yourself. I've...
68kmla.org 68kmla.org

Did you do the SMD caps on the small daughter card in the PSU?
Posted by: cafarmer on 2023-06-18 10:54:37
I did. I was really hopeful about that one, but it didn’t work. 🙁
Posted by: Phipli on 2023-06-18 10:57:05
I did. I was really hopeful about that one, but it didn’t work. 🙁
Replacing the capacitors or the adapter didn't work?
Posted by: cafarmer on 2023-06-18 11:31:41
The caps.
Posted by: Phipli on 2023-06-18 11:44:09
Have you inspected components for scorch marks or damage, such as little burn spots or cracked casings.

Did you clean the boards after recapping (electrolyte conducts electricity).

Does the power supply provide 5V on the tickle voltage pin when plugged in? If you're looking for a pinout, it is the same pinout as a number of other machines, the IIci is probably the most likely to return results.

I would consider testing the board with another PSU - do you have any other maxs of a similar age? IIcx, IIci, IIvi, IIvx, Q700, C650, Q800, P600 or PM7100?
Posted by: cafarmer on 2023-06-18 13:07:19
I did clean the board after I was done and I do have another PSU I put in and tested - still did not work. (I can’t vouch for the other PSU I tried, but it was odd it did nothing different- may mean nothing).

I did see the information in another thread on how to test the 5v and relay. I am going to try that tonight.

Thanks!!
Posted by: cafarmer on 2023-06-19 12:26:21
So quick update: I pulled the daughterboard out of a parts power supply I had (it was dead for other reasons) and the condition of that daughter board was way better. So I recapped it and soldered it back in. I tested the 5v and the relay. Both appeared to pass. I thought I was on the road to recovery except that when I put it back in the IIsi and pressed the button, it turned off and on like three times; "click, click, click - off". the power light corresponded to the clicks. I saw another thread where the guy replaced the two big caps and that fixed this problem. So I will try that next (my recap kit also said "don't usually need to be replaced").

Thanks!
Posted by: Phipli on 2023-06-19 12:27:37
So quick update: I pulled the daughterboard out of a parts power supply I had (it was dead for other reasons) and the condition of that daughter board was way better. So I recapped it and soldered it back in. I tested the 5v and the relay. Both appeared to pass. I thought I was on the road to recovery except that when I put it back in the IIsi and pressed the button, it turned off and on like three times; "click, click, click - off". the power light corresponded to the clicks. I saw another thread where the guy replaced the two big caps and that fixed this problem. So I will try that next (my recap kit also said "don't usually need to be replaced").

Thanks!
CLICK CLICK CLICK is usually a short somewhere.
Posted by: cafarmer on 2023-06-19 13:26:59
CLICK CLICK CLICK is usually a short somewhere.
Going over it now. Yeah, seven clicks then off.
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