Amiga 4000 restoration progress

[LambdaCalculus]

Looks like my Amiga 4000 restoration may be a little more involved than I thought; I took a quick look at what's going on with my Amiga 4000 to see if I can diagnose its issue. It's a little tougher than I thought: the machine powers on but shows only a black screen with some noise. I tried pulling the SIMMs to see if maybe one went bad and left only the chip RAM, but it's still not working. I've done a temperature measurement and found that the machine seems a bit cool in running.

As this is my first big box Amiga, I'm going to need the advice and guidance of some big box owners to see what's going on here. I noticed a little corrosion on the SIMM contacts, so I need to clean that off a bit. That may make some difference. The HDD isn't hooked up, but I don't think that should affect anything. I also don't have the A4000 keyboard; Amiga Bill said that he'll try and locate one for me, but I know that the A2000 keyboard uses the same 6-pin mini-DIN connector (the PS/2 connector) as the 4000 keyboard, so I can make do with one if need be.

If anyone on this board who knows Amiga 4000s well can take a look at my video and chime in with advice, I would be most grateful.

[intric8]

I'm not a 4000 expert by any means, but your HD is not the problem. If the system was working and the HD wasn't connected the KickStart would at least push you to the Workbench Prompt screen. You've got some sort of hardware issue (duh, you already knew that). Black screens are tough because you aren't being given a shred of anything to go on, but if you're seeing noise I have to think you're getting at least some sort of video issue at a minimum.

But here's the thing. The 4000 is prone to capacitor issues, just like the 600/1200. You very well could have bad caps. You might should ping Acill and get in line if you don't figure it out. He might even be able to troubleshoot it for you.

You'd have to pull the board.

He's stacked with business but if you're not in a major rush he's supposed to be A+.

[LambdaCalculus]

According to the previous owner, the board was recapped. But I may have it done again just in case it was recapped incorrectly.

I'm going to pull the machine apart further over the weekend to re-seat everything as well. The SIMMs are all removed to clean tarnish from the contacts. The Varta battery is getting snipped out and the coin cell kit I bought put in its place. I'm also removing the Zorro daughterboard and cleaning all the contacts on it as well.

This Amiga will live!

[mattsoft]

+1 for Acill!

[intric8]

That damned varta battery ... why/how could you re-cap a board and not pull that stupid thing? That makes absolutely no sense to me at all.

The #1 killer of Amigas right there. It blew away one of my 2000s and turned it into a parts machine, sadly.

[LambdaCalculus]

Me neither! If I were doing a recapping, that would be the first thing I get taken off!

[madgrizzle]

...but I know that the A2000 keyboard uses the same 6-pin mini-DIN connector (the PS/2 connector) as the 4000 keyboard, so I can make do with one if need be.

The A2000 uses the old AT-style connector, not PS/2. The A2000 works on an A3000 (same connector). But I read elsewhere a standard AT-PS/2 adapter will work to get a A2000 keyboard connected to a A4000.

[LambdaCalculus]

Well, I did find out one thing wrong, now that I took the A4000 apart yesterday: the Kickstart ROM chips are mismatched! One is a Kickstart 3.1 ROM; the other is a factory installed KS 3.0 ROM!

Yup, that's gonna be an issue! Gotta get fresh ROM chips!

[pgovotsos]

You said you pulled the fast memory SIMMs and left the chip memory in. Black screen is often chip memory. That could be the one that is bad. After cleaning the contacts (softly with soft pencil eraser and IPA) try one of the other SIMMs in the chip memory slot. Are the sockets themselves clean and clips not broken? A soft toothbrush with IPA can be used for them. Gently wiggle the SIMM sockets. Are they firmly attached or is there some wiggling?

But yeah, the Kickstart chips could definitely be the only problem indeed. Would definitely clean the memory and sockets anyway - it wouldn't hurt.

Really silly question - have you pressed down on all the socketed chips to make sure that they are all completely seated? Other than the replaced battery, is it completely stock? No mods like 64MB or PIO?

[LambdaCalculus]

You said you pulled the fast memory SIMMs and left the chip memory in. Black screen is often chip memory. That could be the one that is bad. After cleaning the contacts (softly with soft pencil eraser and IPA) try one of the other SIMMs in the chip memory slot. Are the sockets themselves clean and clips not broken? A soft toothbrush with IPA can be used for them. Gently wiggle the SIMM sockets. Are they firmly attached or is there some wiggling?

The SIMM sockets are all in good condition; no broken clips at all and all sitting firmly in place. The Chip RAM SIMM is a 2MB SIMM; the rest of the SIMMs are 4MB each. If I need to get new SIMMs, I have a friend in California with tons of vintage hardware parts I can ask him for.

Really silly question - have you pressed down on all the socketed chips to make sure that they are all completely seated? Other than the replaced battery, is it completely stock? No mods like 64MB or PIO?

All of the socketed chips feel firmly seated, but there's not many that are socketed; only the Buster is (and I'm replacing it anyway with a Rev. 11 Buster) AFAIK. The rest of the machine is pretty much stock; the CPU card is a 68040 at 25 MHz, the HDD is 340MB, and there's only the one floppy drive.