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IIgs battery repair

LaPorta

Well-known member
So, I have finally gotten around to the repair of my IIgs, which got battery bombed over 10 years ago. That long ago, I didn't even know where to start to fix this thing. Honestly, I am very fortunate that the damage does not seem to be terrible. The posted photos show the extent of it. The PSU thankfully looks to have been spared with just a tiny bit of acid spray on the case. What I don't know is what the little things interspersed between the caps are: L1-5 that have those coil things coming in and out of the top. Do they need to be replaced if somewhat corroded? All that happens when the power supply is turned on is that the power light flashes on and off instantly and that is it. That was 10 years ago the last time I tried this.

Other than cleaning the corrosion and checking continuity, any other suggestions?
 

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LaPorta

Well-known member
Here are some more photos of the affected areas. It looks like slots 1 and 2 got hit as well.
 

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LaPorta

Well-known member
got the holder out. Through hole vias were toast, so I drilled them and repaired. Still nothing, so there must be more going on.

Is this a multi-layer board or not?
 

desertrout

Well-known member
Those inductors and caps north-west of the battery filter out the +5/-5 and +12/-12 from the PSU, so I'd check there - the inductors do look a little corroded as you noted, so checking for continuity through those would be a start, and checking C44 too as it looks like it took a hit (or just recapping that whole section tbh).

Here are the schematics for that board: https://downloads.reactivemicro.com/Apple II Items/Hardware/IIgs/Schematic/Apple IIgs - ROM3 - Schematics - Pages from Apple IIgs - Hardware Reference - 2nd Edition.pdf
 

cheesestraws

Well-known member
L1-5 that have those coil things coming in and out of the top

'L' is the PCB designation for an inductor, which is essentially just a carefully measured coil of wire. They're fairly robust: if you want to test they're still there, just check for continuity across them with a multimeter. They only do anything interesting at AC.
 

LaPorta

Well-known member
Updates: C44 was indeed toast, totally open, so I replaced that. Replaced a few others, too. All inductors have continuity. I desoldered connector J22 and made sure all that is good to go. However, it seems that perhaps now the PSU is suspect. I tried to test voltages straight out of the connector...while I know it is not accurate without a true load, it was all 0 volts regardless. I suspect that perhaps there is also now an issue with he PSU. Time to open that up...
 

desertrout

Well-known member
Yep there definitely should be voltages. Keep us posted! Note, some IIGS PSU's have a fuse inside, I'd check that first.
 

LaPorta

Well-known member
Fuse looks good...in fact, everything looks good. No cap leakage even. No horrible burn marks, nothing. Any clues as what I should be looking for as far as voltage from each pin to ground with no load?
 

desertrout

Well-known member
Just tested mine, unloaded (disconnected from the logic board), I get:
Pin 4: +5.20
Pin 5: +11.45
Pin 6: -11.13
Pin 7: -4.87

Screen Shot 2022-05-02 at 11.48.09 PM.png
I haven't recapped mine, but my machine works fine. I suspect my +12 is low though...

As for what to do, I personally don't know what the usual suspects are. But fwiw I'd start with checking voltages at the transformer and around the supply (usual cautions about mains voltage on the supply side), verifying the switch is functioning properly, checking for open resistors or shorts, see if anything stands out. And of course, as you know, caps can still be faulty despite appearances, and probably should be replaced anyway. :)
 

LaPorta

Well-known member
Recap is in order no matter what for sure, just wanted to make sure that there isn't some sort of horrible issue otherwise...
 

LaPorta

Well-known member
Ok,so testing is proceeding on the PSU. So far, I have run various tests:

Fuse: good
Surge protector: good
Rectifier diodes: all good
Inductor coil: continuity between loop leads, none between windings
Those large, RIFA-style caps test good, as do the small ones, too.

Next, I will try and test the chopper transistor. So far, nothing blown. The hunt continues...
 

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LaPorta

Well-known member
Another update: the 1µf, 35V caps (there appear to be two) both leaked all over. I found very subtle, tell-tale signs of leakage. I will need to make sure there is no further damage to surrounding areas. As expected, the caps are totally useless and don't even register on my ESR meter. I know I have spares somewhere, but I think they are buried in my moving boxes :(.
 

LaPorta

Well-known member
Caps came, getting started on the recap.

Question: can anyone check out their PSU? It looks like I have a component cut out of mine! This has never been modified, nor did I see any components rattling around inside. Check out the photo attached, right in the middle. Are people missing the same thing on theirs?
 

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LaPorta

Well-known member
Well, very good news: with the blown cap on the logic board replaced, and the two corroded 1 µf caps changed in the PSU, I get clean power within spec, and the B&W startup screen for the IIgs out of the composite video port. Good power on chime with a test speaker as well. So, I guess that is all that was truly wrong with it. Now, to recap the rest and test the unit further. Thank you for the voltage diagrams!

Keep tuned for the rest of this repair.
 

desertrout

Well-known member
Nice! Thanks for the update.

As for that apparently clipped resistor, my IIGS's PSU is a little different; mine has a resistor there, but all of the values of the neighbouring resistors are very different that what's on your board...
 

LaPorta

Well-known member
Thanks for the PSU info...I suspect a different revision or something.

So, not all went as planned. Recap proceeded nicely on the board without issue. However, now I have no sound. I get an initial pop from the speaker, but that is it. So far as I can tell, everything is in order. Cap specs are right, orientation is right (plus none blew), and the solder work looks solid. I'll take photos of the area.
 

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LaPorta

Well-known member
A test speaker (from an SE), but it is virtually identical and worked prior to the recapping.
 
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