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[spirantho]

I wish it were as simple as the oscillator! If that were the case though then the CS-PPC would still be working, as that uses the external clock.
D-175 is the diode seperating the PSU's +12V line and the usable +12V_USER line. It's got a voltage drop of about 0.7V which I think is correct.
I think again you're right about the +12V line being just for the audio amp, but I believe the Amiga checks for a steady +12V rail before booting doesn't it? This is the usual cause of A600s not booting, I believe. It certainly looks like this is what's happening, anyway...

[paul1981]

Originally Posted by spirantho

I wish it were as simple as the oscillator! If that were the case though then the CS-PPC would still be working, as that uses the external clock.
D-175 is the diode seperating the PSU's +12V line and the usable +12V_USER line. It's got a voltage drop of about 0.7V which I think is correct.
I think again you're right about the +12V line being just for the audio amp, but I believe the Amiga checks for a steady +12V rail before booting doesn't it? This is the usual cause of A600s not booting, I believe. It certainly looks like this is what's happening, anyway...

The 28MHz clock is required for the custom chips and video circuit. This is always in use whether you have an accellerator card or not.

[spirantho]

Just swapped it (the crystal) and it didn't improve. I had to swap it with a non-known-good one though (from a broken A600) so it's possible it's broken on both, but I doubt it. Going to fix the A600 and see if it works with the crystal to find out.

[Boot_WB]

Originally Posted by spirantho

Hi people,

Still fighting my A4000.
Occasionally it boots, and I'm fairly sure now it's to do with the CPU connector. I've got the voltages up nicely, so that should be ok.
I've cleaned and re-cleaned the CPU connector but it's so bloomin' difficult to get at, I still can't be sure it's clean.

Anyhoo, the symptom at the moment is a bright magenta screen on a cold boot. I know the CPU is basically working because if I remove the chip RAM, then it sure enough boots to a green screen.
Very occasionally I get a white screen.
Quite often I get nothing at all - just a dark grey screen as though the CPU is doing nothing.

I've tried with both the original 030 module and the CS-PPC, same thing on both.

All this time the Caps Lock light works as it should, no error codes or anything there.

Anyone got any ideas? Thanks if so!

Hi Ian,

Have you tried pulling & cleaning the ROMs, and checking for any broken legs? May also be worth checking the DIL socket solder joints to the motherboard also.

Purple Not an "official" color, but may be caused by
bad ROMs.

http://web.archive.org/web/200810181...s/A4k-HW3.html

also

http://www.amiga.org/forums/showthread.php?t=35177

[spirantho]

I just checked the ROMS - they contain the correct data, so that's ok.
I think I'll check the connections next.... I've already tried reseating them, they're both good.
One person in that thread said that he had a similar problem with leaking caps on the sound module - that'd imply a +/- 12V line error, though, which I do suspect....

[spirantho]

Well.. I found the cause of the mysterious magenta boot screen!

One time when my A4000 managed to boot, and it was sitting on the insert disk screen, the screen suddenly went magenta again.
But what was weird was that the screen then filled with white lines.... but I could see the insert disk screen in the background!
I quickly checked Alice's temperature, to see if it was hot, and... the lines disappeared!
Let go of the chip... lines return. Press on chip, lines go. Hah!
One quick reheat of the chip with the Aoyue SMT rework station, and the problem got worse - black screen with bad sync.
Not giving up, I took Alice off completely, put a bit of fresh solder on some of the pads, put Alice back on...

Bing! Machine boots! First time! And second time! And every time for the last 30 or so attempts.

So if your A4000 doesn't boot, and you get sporadic booting with no obvious symptoms, just maybe you just need to resolder a custom chip or two.

Hurrah! Now I think I'm going to find a heatsink for Alice.....

[mechy]

Good job Spirantho. in all the A4000's i have had/worked on i have yet to have to resolder any custom chips due to bad contact. it was always something else.I guess you must of got a friday board(they were in a hurry to get to the bar after work) lol.
good job finding it. that was a tough one.

mech