Performa 475 Repair

Original thread and symptoms: Requieum for a Q605, repair or . . .

Interesting, you're already doing the Pizza Box toggle switch method for getting the Video Circuitry fired up without a battery in the second instance: Boot chimes, pause, four rising notes, pause, then four falling notes. I hadn't noted any differences in the tempo of the death chimes due to battery state, hrmmm? I remember my notes on the FDD Cage saying VRAM was required, I wonder if just one SIMM from your LC is enough though, does it need a pair? One of my LC VRAM SIMMs actually says something like "For LC Use only."

BTW, you forgot to mention that you were expecting to receive something I cobbled together for you using that guaranteed non-working MoBo in the nicer of my pair of 475 cases.

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Yup sounds like the MB needs a re-cap.

They all need re-cap's these days.

I was wondering the same thing too. How much vram does it really need? I think the 475 originally came with 512k. I wonder if the SIMM from my LC ii is just 256k.

either 

2- 256k's

or

2- 512k's

I'v used "LC only" vram in a LC475 before.

Not sure if i got lucky, but it worked.

Going to recap tomorrow after the board is completely dry. First, for the caps should I wiggle them off or apply fresh solder and lift while melted? Second, how should I properly clean the board? I have 91 percent alcohol, but the last time I washed a board it left white areas after it dried that I had to reclean.

You using tap water or distilled water? I found deposits when I used tap water, but they came out clean with distilled water. Also add some acetone to your water/soap/alcohol mix to cut the cap goo that might be under the chips. Some people add ammonia to cut the cap goo.

I prefer to wiggle the caps. It makes it easier to clean up. But if the pad is really rotted, it's going to lift no matter if you wiggle or desolder the cap.

Good luck with your recap.

I wiggled 3 off and they came off fine. Just takes so long to wiggle. I used tap water on my Color Classic board but then washed it off in alcohol. I guess I should get some distilled water and some kind of container to wash it in.

Any luck with this?

All the caps off, gave it a bath last night, new caps tonight. Crossing fingers. Still can't seem to scrub off a little bit of corrosion on one of the chips. If it doesn't boot, may have to replace that next. Its not too bad.

After washing, have you tried straight acetone and a tooth brush on rough spots? If not, try it. It should work.

After the recap, still doesn't work. Happy chime then instant death chime. A few lucky times of using the red button on the motherboard, I didn't get a death chime.

You get video and an attempt to boot the hard drive? If you get video and it tries to boot the hard drive, then that means the drive has bad boot blocks. Disconnect the drive and see if it gives a flashing "?" in a floppy icon.

Mine only chimes and then nothing. Dark screen, no chimes of death and nothing happens. See for details: https://68kmla.org/forums/index.php?/topic/22427-macintosh-performa-475-chime-but-no-video/page-2&do=findComment&comment=251843

No hard drive. No video. The one time that it didn't death chime I didn't have a monitor hooked up. I put a floppy in but I couldn't hear if it was doing anything.

Its more or less the same problem I have then, but you get the Chimes of Death, mine don't.

Still trying to find bad traces. Been testing in the ram area but can't find anything.

have you tried baking it in the oven @ 200f for 30 min?

make sure to remove the pram battery.

200°F? That's not hot enough to melt solder which is at 368°F. There has to be a reason for 200°F because this is not the only time I seen this number around. What does experience says?

Everyone has different methods... I just use a heat gun on high for reflows... I do NOT know how hot high is though

200 I'm sure is for drying and getting contaminants off.

400 for 10 min for reflow is what I found what works for me more often than not. It's about 90 percent success rate for me, newer and vintage at this point.

I as well have the exact same issue with a Performa 475 although mine worked perfectly and I was using it, turned it off then on at a different time and this issue started to happen. Recapped it and still same issue. I believe this to be a memory issue though as others have mentioned that a happy chime first followed by a sad chime is a memory issue. Did you ever figure this one out?

Just because it looks like it is a memory issue does not mean that is a memory issue. Rotted out traces to the RAM's Data, Address, Read/Write and Memory Refresh Strobe lines can kill signals going/coming to/from the RAM, thus making it look like a RAM Problem when it is not.

One has to go in with an oscilloscope or multimeter and check every line going to the RAM and fix those lines that registers as dead. Complicating things further, those Data, Control and Address Lines going to the VIAs and other support chips can also add to this problem and they need to be checked out and fixed too. Adding tot he complication even more, rotted solder joints on the chips and the board will add to the problem, so they need to be desoldered, cleaned up and resoldered with fresh solder.

Besides the proof being rotted traces on the board, the other proof to this is that the RAM used in my 475 works well in other machines I use to test it on, so I know the RAM works. The problem is with the board, not the RAM.