VOGONS


First post, by Unite

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A while back I picked up a faulty Packard Bell Executive. From what I can tell going from the jumper settings its a 486DX at either 25 or 40mhz but I'm having some difficulty in finding any information about the motherboard.

The machine is faulty. It'll power on, the HDD spins up (I love that old seek test sound) the HDD access light flashes but that's it. No floppy seek, no beeps, nothing on screen.

There isn't any ram installed in the simm slots but the diagram on the lid makes me think that this board has inbuilt ram. It mentions a jumper for on-board DRAM enable / disable.

The fault I'm 99% positive will be down to the leaking varta and corrision on the board at its location which also just happens to be beside the above mentioned DRAM.

So first question is am I correct and this thing has on board system memory or does DRAM refer to something else?

I have an old Apple Mac with an 8MB EDO simm in it that fits in the 486 but I was wondering if that will work as I thought apples back than have proprietary ram? I don't want to be attempting the repair without knowing anything else I install is suitable or not.

I know its probably not worth saving but I fancy giving it a go just to see if I can repair the damage. Its not the most exciting system, no PCI slots but I think getting it up and running, stick a sound card in there and it'll make a decent wee machine to play with.

I've posted a few pictures below of the motherboard,the case badge and the diagram on the lid if someone can help me identify the board and let me know if you think its on board system memory or not?

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Reply 1 of 9, by CuPid

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It's definitely worth keeping it and trying to fix it. It's in very good shape and very clean at 1st glance.

Is there any chip at the location mentionned as "DRAM" at the top of the diagram ? (the location under the drives is not visible on the pictures).

Besides, there are no cache SRAM chips, if they were removed you should check that the jumpers are then not configured incorrectly (that could prevent the boot).

I need a vacation.

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Reply 2 of 9, by Unite

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There are various chips located the the DRAM position top right of the diagram. There is also a fair bit of corrosion all over this area so I'll probably need to get the desoldering station out and remove them to clean up.

I'll check the jumper setting for the SRAM but I get the impression this machine has never been opened until I got it. I don't think its seen a lot of action in its day as the HDD doesn't have that much on it. Just all the pack in software and a few documents.

Once I get into it in more detail I'll take a few pictures and keep this thread updated.

Reply 3 of 9, by dionb

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Unite wrote:

A while back I picked up a faulty Packard Bell Executive. From what I can tell going from the jumper settings its a 486DX at either 25 or 40mhz but I'm having some difficulty in finding any information about the motherboard.

Check the sticker on the BIOS EPROM. It's a PB430.

Here's the jumper settings & specs:
http://uktsupport.co.uk/pb/mb/430.htm

Quite a nice mid-period 486 board with sensible onboard bits and decent expansion options.

The machine is faulty. It'll power on, the HDD spins up (I love that old seek test sound) the HDD access light flashes but that's it. No floppy seek, no beeps, nothing on screen.

There isn't any ram installed in the simm slots but the diagram on the lid makes me think that this board has inbuilt ram. It mentions a jumper for on-board DRAM enable / disable.

If there's onboard memory and there should be, it's in the bottom right-hand corner, under the floppy bay.

The fault I'm 99% positive will be down to the leaking varta and corrision on the board at its location which also just happens to be beside the above mentioned DRAM.

So first question is am I correct and this thing has on board system memory or does DRAM refer to something else?

Generally a good idea when troubleshooting dead systems is to remove the board from the machine, then test outside it (to rule out short circuits). Also helps making stuff visible. We'd need a pic of the area with the RAM - and a hi-res one of the battery damage could also help. Also, if the battery's leaked, get it out asap, drench the area in vinegar, brush with an old toothbrush, then rinse liberally with water and allow to dry.

The other DRAM is for the VGA. That is visible, the single SOJ chip just below the GD5424

I have an old Apple Mac with an 8MB EDO simm in it that fits in the 486 but I was wondering if that will work as I thought apples back than have proprietary ram? I don't want to be attempting the repair without knowing anything else I install is suitable or not.

If it's EDO, it won't work. This board is FPM only.

I know its probably not worth saving but I fancy giving it a go just to see if I can repair the damage. Its not the most exciting system, no PCI slots but I think getting it up and running, stick a sound card in there and it'll make a decent wee machine to play with.

Onboard VGA and I/O runs off a VLB bus, so it doesn't need PCI. This machine accepts any 5V So3 CPUs, so it really is quite nice to play with. If you get it up and running, add L2 cache + tag in those five DIP sockets (otherwise it's a slug), stick in a sound card and enjoy 😀

Reply 4 of 9, by Unite

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Many thanks for the detailed reply.

I pulled the board out last night and its a horror show. This one might be to far gone but I'll give it my best. I have some experience repairing damage from Varta leaking on my Amiga 500+ but this is another thing all together.

It'll be fully cleaned down tonight. I'm hoping its worse than it looks but there are already a fair few traces that I can see are just gone.

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I've got a fibreglass pen so I'll go over the worst of it and start testing traces and start repairs. My main concern is under the SMD components on the top of the board. I can remove them easy enough with the rework station but getting them back on it were I struggle.

Reply 5 of 9, by Miphee

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For the future, never plug it in with that kind of damage. Half of the pins are probably shorted and powering it up in that condition just gets power to all the wrong places.
That board looks far gone IMO and I've repaired a ton of acid damaged boards.

Reply 6 of 9, by Unite

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Yes if I had of knew the full extent of this damage there is no way I'd of powered it up. Less learned though, remove the board to inspect fully before diving in.

I'm leaning heavily toward this thing is toast but I'll give it a couple of hours tonight, remove the corrosion and see just how bad it is.

Reply 7 of 9, by Miphee

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The main problems are under U52, U55, and U59. There is so much green gunk that it's nearly impossible to tell what traces go and where.
Most of these traces are already dissolved an you only see the lacquered outlines. Cleaning removes these as well. Removing the affected ICs are probably unavoidable.
The solder side is a little easier but don't forget to make high-resolution photos of the affected area from many angles. This will make it easier to identify trace paths.
You are looking at many days of work with this one.

Reply 8 of 9, by dionb

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Ugh, looks depressingly familiar. Found a PB430 last year. Same story.

Tbh the component side doesn't look too bad. U52 is toast, but that's probably just 74-series logic, easily replaced. Not sure about U55 and U59, they might still be OK after thorough cleanup.

What I'm more concerned about is that big bundle of narrow traces on the solder side that goes straight through the affected area. Probably most if not all gone. Theoretically fixable, but far more of a pain than a few SMD bits.

Reply 9 of 9, by Unite

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I thought you lot at least desired an update on this even if it isn't good news. The board is too far gone, really really gone. I spent maybe 3-4 hours cleaning up whats left and stopped counting at 30 broken traces and just plain lost count of vias that are simply not there anymore. While it probably could be fixed if I spent weeks at it I've just drawn a line under it and pinned it to my motherboard art on the wall.

The question now is what to do with the case that's in rather good condition. Do I try to source another board or should I use the case as a basis for my man cave htpc? I leaning heavily towards the htpc idea just because its a bit different and I have most all the parts for that build sitting ready to go. Would need to make a custom back for the case though...