IIsi power supply recap?

[bigmessowires]

My IIsi has started acting up again, and I suspect the power supply. How difficult are these to recap, compared to the logic board? 

When I first got this machine, it had trouble starting up, and would only start from the power switch and not the keyboard power key (or was it the other way around). Uniserver recapped the logic board a year or two ago, and after that it was fine, but more recently it's started having trouble again. Now I can barely get it to turn on at all.

Symptoms: when I plug in the power cord, sometimes there are noises coming from within the PSU, like something's trying to turn on. After that, I once got it to boot from the rear power switch. But since then, either the power switch or the keyboard power key causes a brief "click" sound somewhere inside the computer, but nothing more. No fans or other signs of life.

 

[techknight]

it is widely known the IIsi, especially the Sony version of the IIsis power supply, needs recapped at this point. 

 

[bigmessowires]

Any special considerations when recapping a PSU? I'm a little intimidated by all the "danger" stickers on the thing, but I assume if I let it sit for a few hours unplugged, the caps won't have any significant voltage left in them. 

 

[techknight]

When I see a danger sticker, I want to open it faster. What are they hiding? ahaha. thats just me. 

I think there is a riser/hybrid PCB in there that contains two small electrolytics that love to leak and eat the PCB, As well as all the main radials on the output. 

 

[bigmessowires]

Yeah, it's the Sony with the riser card. I opened it up, and nothing looks obviously exploded, not that that guarantees anything. Everything is covered in gobs of hot glue, what a mess. I thought that riser card was socketed, but it's soldered in. Would hot air work to desolder that, without desoldering half the other components in the process? That's the only desoldering tool I've got besides a little Chipquick.

 

[epooch]

So true...

When I see a danger sticker, I want to open it faster. What are they hiding?

 

[Elfen]

From Uniserver's site...

http://maccaps.com/MacCaps/Capacitor_Reference/Entries/1990/10/5_Macintosh_IIsi_Sony_Power_Supply.html

 

[uniserver]

yeah they are a little annoying but i do enough of them that i am really good at it.... you would not believe how many IIsi's are still in service running CNC, MILLs,  Laser OXY water cutters.   automation....   so many different places these are in use.... the IIsi and the Iici as well. Iici psu's suck ass too.

 

[techknight]

It would be awesome and cool to have an industrial machine that relied on those for everyday use. Then I could say I had a purpose for my collection! but sadly I cant. 

Closest thing I have is a Precix full size CNC machine but it runs on a P166. Meh... 

 

[bigmessowires]

My recap job on the IIsi power supply is complete, but I'm not brave enough to try turning it on until tomorrow! I kind of wimped out, and only replaced the three capacitors that seemed most likely to be causing the problem, based on this thread. That was C105 (a high voltage cap on the mains side) and the two caps on the riser daughterboard. But it wasn't too bad, and now I'm thinking I should probably have done them all. 

The whole process took me about 3 hours, and was my first time recapping anything. Removing and replacing the through-hole stuff wasn't difficult, though it was a little bit time consuming. I bought a $13 soldering iron with a built-in spring-loaded solder sucker. Just put the iron over the pin, hold for a second, then press the button to release the plunger and mostly all the solder is sucked up. I used this to desolder the daughterboard too. I had to revisit a few pins to get them totally clean, but overall the process was simple. I don't do enough desoldering to justify the cost of a fancier desoldering gun with a continuous suction vacuum pump, so this seemed like a good tool for occasional use.

I removed the two SMD capacitors on the daughterboard with a hot air tool. I'm not sure how you would do that without such a tool - just rip them off with pliers? The hot air worked fine, except... when I used tweezers to slide off the caps after the solder had melted, I accidentally pushed one of them right through a bunch of other little SMD components, whose solder had also melted, and ended up with a jumbled heap of little components half soldered together in a corner of the board.  :O  But with some patience I was able to separate them all and get things cleaned up, and I think I even put everything back where it was originally! Or so I hope.

 

[bigmessowires]

IT WORKS!! Oooh yeah, I feel like Superman! My IIsi is back in business. Before it would rarely ever start up, and when it did, it was impossible to turn off again except by unplugging it. After replacing those three caps, now everything is a-ok. I can boot from the rear power switch or keyboard power button, and the soft power-off function works again too. Boy, that feels good.

I won't be so timid about recapping next time the need arises. If I hadn't blundered by knocking off a bunch of unrelated SMD parts, I probably could have done the whole job in about an hour.

 

[techknight]

The great god at creating the floppy emu, the device where I would have had no idea where to start, Brought timid by recapping? Naaaaa... no way. 

 

[uniserver]

it should get you by for a little while.

but really though every lytic should be changed, the only ones you could skimp on are the 2 HV smoothing caps.

 

[CC_333]

...the only ones you could skimp on are the 2 HV smoothing caps.

But those will eventually fail also, right?

c

 

[uniserver]

I think its more likely for those to go bang with the 230volt peoples.

technically any 120v - 230v auto psu, has those hv primary caps rated for 230v use, so running them at 120v

way less then what they are rated for there for they last longer.

anytime you take and put a Higher voltage cap in for what was previously there its going to last longer.

I have taken apart some quality made in ITALY IIsi psu's and they used way over voltage caps for the rails.

like 25v and 35v and like what i use, and none of them were leaking, at all.

 

[bigmessowires]

The great god at creating the floppy emu, the device where I would have had no idea where to start, Brought timid by recapping? Naaaaa... no way. 

We all have our failings.

I'm more comfortable building things than repairing existing things, but it's all mental. If I screw up while building something, then nothing is really lost because I didn't have anything to start with anyway. But if I screw up while repairing something, I could make things much worse or possibly destroy it beyond repair, so that's why I get shy. Although I can't actually think of any examples where I destroyed something while trying to repair it, so it's more like a strange phobia than a rational concern.

 

[uniserver]

yeah dealing with this , being knee deep in if for this time, has given my mental skin a thick leathery protection. so many issues do arise but i just roll with the punches these days, and just carry on.  The only thing i am getting away from is when people want me to work on battery killed stuff... i just don't do it... unless they send me really good pictures showing maybe just the battery holder rotted off or something.