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Trying to fix a IIsi - Power supply oddity + possible display issues?

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I'm brand new here, but not new to Macs at all having grown up in the age of the Apple II and the very early macs.  I was hankering for my old 68k mac days and I picked up a Mac IIsi to restrore.

My first task was to recap the power supply. my first time doing such a thing though I do have a little electronics experience, just nothing quite this involved.  It had a lot of leakage but isn't near as bad as some I've seen in the many videos I watched.  The motherboard itself was in very good condition but it would not start up but the fan did work.  I recapped the motherboard and it now chimes and I can then hear the hard disk spin up and start cranking away.  All good right?


Well not entirely.  First off I've yet to get any Mac -> VGA adapter to work.  I had one with no switches, so I tried getting with switches but I've yet to find a setting that works with this newer Dell LCD i'm plugging it into.  I've read up a bit about sync on green and how some older dell monitors will work and I have one on order.  So for now I'm still hopeful the display will work and I've just not been using a monitor that can handle its early 90s way things.


The bigger problem is with the power supply.  It seems to put out correct voltages at least on the SCSI drive molex (12.16v and 5.06v, but close enough) It will run for about 2-10 minutes and suddenly start flicking on and off rapidly making the LED flash and the speaker bark like machine gun fire.  I've rechecked all my caps and solder joints, doesn't seem to be that.  I'm wondering if its warming up and something else is parting?   Could it be the switch or even the relay?  Anyone ever experience anything like this?  So far I'm stumped!  I did read that the switch has can be turned with a coin to either stay in constant power on, or back to push-toggle.  I've also noticed I can't turn the machine off with the switch, it just resets.  It doesn't even do that always when I first turn it on, for a bit it will simply do nothing and then after about 1 min or so, it will simply reboot the machine, not shut it down.  If I turn it to stay on position, it still machineguns on me, but there is a delay between.  Sometimes when I bounce it with the switch the machinegunning will stop and it will start to work normally but within 10 seconds will go back to click-click-click-click.  Sometimes the relay is jumping during that but not always.


So relay?  Switch?  Or is something else afoot?

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Did you also recap the small daughter board inside the PSU?


That will give you intermittent power on/off issues. It's a bit of a bear to desolder all of the pins to get the board out, but it's definitely required recapping.


Good luck!

Edited by jessenator
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image.thumb.png.f3d65b6d9dbf0853887d6600e708211f.pngimage.thumb.png.957551013dcc3b85035e858402b44f5e.pngOk, I removed the daughtercard and resoldered one of the smds that was a little suspect in its soldering.   have better soldering tips now too, so I think I did a far better job putting both the SMD and the daughtercard itself back on.  Much neater joints!    I let it run a while and no stutter yet!  Next up is the display.  I have an adapter pictured above, trying to connect this to a HP S2031 LCD.  Anyone know what settings I should be using for the IIsi by any chance?  I've tried a lot under mode 6 (sync on green) with no luck.  

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re: the video, a lot ink has been spilled on how picky beige Mac's can be with LCD's, even with an adapter. Your Dell may simply not be compatible. I've been lucky with the Samsung SyncMaster 730B's I happen to have - I've often seen them (or similar models) at thrift shops for $5-10. I have what looks like the same switch-type adapters, with the switches 1, 2, 3, 4 turned on. Other folks will swear by the models they use, so check around here and on Google, you'll find more info. There may actually be a 'thread to end all threads' about this topic here...


re: power, definitely check your work, and clean your work with isopropyl alcohol (90% or better). Sometimes getting these awesome old machines up and running can be slow, tedious work, but it's worth it. :)

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I was able to make the IIsi talk to a NEC Multisync EA190M and a Panasonic Panaflat LC50s but not to a DGM 19" display. The latter works with nearly all my classic Macs though - but it also refused to cooperate with a NeXTstation so maybe it's the display itself. I think NEC MultiSync monitors have a very good track record being able to connect to nearly any signal.


When I looked at the schematics a while ago I found them slightly different in the display circuitry compared to other machines from that era (notably the LC) so the IIsi might be the "odd one out".


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Success!!!  I have gotten the system working now, I had to buy an old Dell LCD that was known to work with vintage machines.  Using a Dell 1707FP 17 inch LCD, works great!  I found that the correct settings were 1 and 2 on the adapter I have.


On the power supply I replaced the two large 250v 220uf capacitors and it no longer clicks on and off rapidly.  Seems they must have been on the edge of death and would act up on heating.  I spent about 30 minutes on the machine without any issues.  I've plugged in the Rominator II and after an initial sad sound, remembered I had to set the W1 jumper to use it.  The machine would not boot from ROM until I booted off the HD and put the machine into 32 bit addressing mode as it was set to 24 bit mode.  Good thing the HD worked!  It has a 120GB quantum drive which seems to work well for its age!  The OS was locking up on startup but booting with extensions off let me set the date/time and then it started booting with them back on.


The floppy seems dead but I need to open it up and clean it out and go over it and see what needs replacing on its board. I see tiny electrolytic caps and I suspect they will be no good.  If I need to put things on in a pinch, I do have a Floppy EMU though I'd have to get it reflashed out of Apple II mode.  I might pick up a second just for vintage mac use.


Other than the floppy issue, the only other thing is when I shut down the machine it clicks off and immediately back on again.  So something is still not quite right but at least it is staying on without issues and the keyboard soft power on and reboot also works fine.


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