Performa 600 on the way out?

[Mr. Ksoft]

Hi, first post here. Nice to see a community for the ol' 68k Macs.

I have this Performa 600, stock except that it has been upgraded to 20MB of memory. It was my first computer, so I've kept it around for nostalgic purposes even though it is such a terrible performer in the Mac world. I pulled it out of storage back in 2007 after it had languished in there for seven years, and it had trouble booting, and would randomly shut off. I traced it to a dead PRAM battery, replaced it, and things have been smooth sailing ever since.

Until yesterday! I haven't used it in a few months, but I was going to yesterday. It gave me the friendly chime, and got partway through booting System 7.1P5 when it just shut off. So I powered it on again. Ran for just a few seconds, then shut off. Frustrated, I tried a few more times, and it shut off even faster every time.

This reminded me of when I first pulled it out, so I thought maybe the PRAM battery went. So I swapped it with a relatively fresh one that I know is working from one of my Power Mac 6100/60av's. No dice, same deal. I pulled that battery out, tried a few more times... and then it just completely stopped doing anything when I pressed the power button. Frustrated, I left it.

Today, I plugged it back in and decided to try once more. It powered up again! And ran for four seconds, then then the same cycle happened all over again.

What's the deal with it? I'm guessing the power supply is toast, but I don't think I have anything that can be substituted. My only two other Macs are both Power Mac 6100/60av's. Anybody who's better with Macs than I want to weigh in?

 

[beachycove]

I'd begin by inspecting the logic board for capacitor leakage.

My first Mac (bought new) was a P600 too.

 

[Mr. Ksoft]

Hmm, there are very few caps on the board that I can see, but none of them appear to have leaked. The logic board looks nice and clean.

 

[beachycove]

There are tech and electronics savvy members who occasionally visit who could tell you more about testing the ps with multimeters and such.

What I can say is that the P600 ps appears to be common to it, the IIvx, the Centris and Quadra 600, and the 7100. If it is the ps, it ought to be reasonably easy to find a replacement for it. As these are not high demand machines (most find them ugly), there are plenty of parts about.

I'd try fixing it first, however, and on the repair side of things, I would advocate a low-tech approach in the first instance, since there are things that anyone can do. I more or less routinely clean the logic board of any machine older than around 1995 that comes in the house these days because of the frequency of capacitor failure. The latter can be hard to spot, and though ultimately the caps will need to be replaced in the machine, cleaning is necessary anyway as part of the replacement process, so why not give it a go and see if it works, I say to myself. And it generally does work; my only failures to cure problems to date are an SE/30, which did not respond either to washing or to capacitor replacement, and a 9500, which is just plain dead. My 30 or so 68k machines are otherwise working fine. I just use warm-to-hot water under moderate pressure from a handheld shower, spray for a good few minutes, allow the board to dry thoroughly for a couple of weeks or more, and reassemble.

Over the winter, I gave my Quadra 650 logic board — and power supply too — the same treatment after it had begun to act up. It had become progressively erratic and in the end would not boot. So I thought I'd try giving it a good cleaning. It was first disassembled, which provides opportunity to clean the case thoroughly. Treatment of the logic board is fairly self-explanatory. In the case of the ps, I just took the top off and hosed it out. Masses of dirt came out of the thing. I then shook the water out, oiled the fan and put it somewhere where it had plenty of chance to dry and a couple of weeks later I reassembled the Quadra, plugged it in and it works perfectly again. It's scrap electronics; what have I got to lose?

 

[Mr. Ksoft]

I think the problem is in the power supply. (Keyword: I think. To be extremely, extremely honest, I'm mostly a software guy and don't know much about electronics otherwise... and definitely not power supplies) I opened up the power supply (well, sorta, I can only get the top partially off because the connector on the bottom is stuck in place) to clean it out and I noticed some caps had a sort of white goop (yeah, lack of a better word. Sue me.) around their bases or splattered on the sides. I'm not sure if that counts as anything; it might just be some sort of glue... but anyway there's also another thing, in a little plastic container that looks a little like a vertical version of a Mac's PRAM battery holder. It's round like a cap but I can't tell what it is. It's covered in a shiny yellow-red-black dried-up goop. I have no idea if it is something normal, but I did google around for pictures of inside a power supply and didn't see anything like it.

I can supply pictures if needed. But, I might just be being an idiot since I know nothing about power supplies... in which case, I apologize in advance for my stupidity.

 

[Osgeld]

the white goo is almost always hot melt glue, they use that on larger parts to hold them in place while going down the line (or a tinfoil hat theory that over time has become a fact is that it "provides more stability against mechanical shock", eventhough you can pick the crap off with no effort and your finger )

the other thing you describe is most likely an inductor that has been plastic dipped and is quite common in apple power supplies (pc power supplies usually dont dip theirs cause it really is not necessary in most cases, and usually they use doughnut cores, where as apple liked those cylinder ones for whatever reasons)

the best way to check a power supply is looking at its voltages with a meter while its under load (ie computer attached and running)

 

[Scott Baret]

I'm not all that familiar with the IIvx/IIvi/P600, but if the power supply is similar to the IIcx/IIci/Quadra 700 (all three of which I am very familiar with) I will advise to have a spare on hand at all times. Of all the early Mac power supplies aside from the Plus and earlier, this one has to be the most problematic. I've had similar problems with the computer randomly shutting off on my IIci, which was fine once I replaced the power supply unit.

I also once worked on a IIcx that wouldn't turn on. I had forgotten to unplug it (I was repairing several Macs that day at one time) and a few hours later it chimed on for no reason. Ah, the wonder of these old power supplies.

The P600, IIvx, and other machines of the form factor seem to have a different supply overall. You can buy one from Herb Johnson for $29 plus shipping (http://www.retrotechnology.com/herbs_stuff/m_parts.html#power). The P600 isn't explicitly listed, but keep in mind its corporate cousin is the IIvx, so any part for a IIvx will generally work with it.

 

[MidnightCommando]

The power connector on the bottom isn't stuck in place. It's on a metal frame - you'll note that to the sides of the mating molex connector there are two circular pins with flaps on them - like so

ø[       ]ø

If you grab the flaps on the side with pliers you can force those little circular supports back through the metal, and the connector will come right out. Just be careful - if you screw up, you're going to have a hard time mating the SMPSU back to the logics

Also if you need parts, a WTB request on the Trading Post on this forum can be most useful.