VOGONS


First post, by Vegge

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So I've had this machine for a while, a Copam PC-501 Turbo. It was dead when I got it, but I was fiddling with it and got it to boot a few times, then moved on to testing other new stuff. But I took it out again last week and it's completely dead. No Irdy signal on the bootcard, no beeps, just dead.
With Supersoft instead, Irdy is lit and it beeps codes, which seems to be "CPU registers and logic" and some DMA faults. After a while it stops beeping and shows 0102, with flickering Irdy.

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Heres a video of what it does with the Supersoft/Landmark
https://youtu.be/mbn7lni4nP4
I replaced all tantalums on the board just in case and cleaned up some oxide (not much) around the battery. Replaced the 287 socket and added a cr2032 for cmos settings. It might be a little weak though (only 2.55v left at cmos), but 4.5v makes no difference.
All vias are filled with solder so I don't think the battery leaked in there. I have removed crusted solder on some components and reflowed them with a lot of flux to clean it up. As far as I can tell clk signal is present at both 286 and 287 socket.

I've got complete schematics over the board, 16 pages of it. But I really don't know where to begin with this. Anybody got an idea?

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more schematics to come...

Last edited by Vegge on 2020-03-25, 06:35. Edited 4 times in total.

Reply 1 of 42, by Vegge

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...schematics

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more to come...

Reply 2 of 42, by Vegge

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...schematics

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one more..

Reply 3 of 42, by Vegge

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phew

Reply 4 of 42, by xtgold

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tinned chips in tinned sockets are a headache.
I have a scruffy I use (abrasive foam normally used by painters) I clean the chip pins with.
You may try stripping it down to 1 meg of ram and just have a video card installed to check for any signs of life.I have a 286 that is dead but has the shadow ram and 4 other chips stripped out.I don't know what the original chips were.I don't have the luxury of a schematic.

Reply 8 of 42, by computerguy08

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Before you do anything else, remove all the socketed chips (RAM, FPU,etc.) and try to clean the sockets with some deoxit (just to make sure sockets are also cleaned).

Does the motherboard show any activity on the POST card with the original BIOS ?

Ruud's diagnostic ROM would have been perfect here, but I think it is only for XT boards.

Reply 10 of 42, by computerguy08

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Since it had a rechargeable barrel (I assume), shouldn't this board have a clear CMOS jumper? I'm looking at J9. Could you tell me where it leads to (electrically)?

Also, you should double check every trace that looks abnormal (around the battery area especially). Looks can be deceiving.

Reply 11 of 42, by Vegge

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J9 is to jumper between the original keyboard and ibm compatible keyboard.

Traces are measured, the only one with any damage was the one to the battery positive. Jumperwire in place for that one. I can go over the area again just in case. But so far all traces look fine and measures 0 Ω.

No clear CMOS jumper in the manual.
Im leaning more towards componentfailiure. But I don’t want to blindly change parts.

Reply 14 of 42, by Vegge

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Deunan wrote on 2020-03-25, 14:42:

What POST codes do you get with original BIOS, and what brand it is (Phoenix, AMI, other?)

Only 00FF. The LED for ready is lit but not as bright as with the supersoft roms.
https://youtu.be/nHhGMIrlTks
I don't know what type of bios it is.
This is all it shows when I got it to boot. Not much info there. Never got it to boot again after this.

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I dumped both bioses if it helps.

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xtgold wrote on 2020-03-25, 15:23:

dealing with 30 year old chips it could be anything

Yeah, sad but true. but if it can be repaired I'll have a nice 286 machine to play with. I bought it as a package with the original keyboard and the monitor it was sold withwhen new, even got the box for the monitor.

Reply 15 of 42, by Deunan

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Vegge wrote on 2020-03-25, 17:00:

Only 00FF. The LED for ready is lit but not as bright as with the supersoft roms.
I dumped both bioses if it helps.

Checksum is correct so the image is good, but since it dies so soon I'd expect a problem with reading it by CPU. Possibly a cold or cracked solder on the sockets? Worth checking out. It's a nice mobo, a bit of in-between XT and AT. I'd say it can be repaired with some patience unlike the later 286 mobos that are ASIC based so if one of these goes bad it's end of the line. Though frankly these rarely die.

Did you try a manual reset (via a button) after power-on, in case it's a problem with voltates rising too slow?

Reply 16 of 42, by Jo22

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Vegge wrote on 2020-03-25, 17:00:

This is all it shows when I got it to boot. Not much info there. Never got it to boot again after this.

Hm. Maybe it's really related to the clock somehow. Maybe there's a broken diode next to the clock chip ? Dunno.
A non-functional clock also means that the data in the clock's CMOS RAM is affected, which in turn could result in the PC not booting.
In fact, I've seen quite a few 286es that refused boot because of a dead Dallas clock (internal battery was discharged).
Also, if the CMOS works, but contains spurious data, the PC may also refuse to boot.

Vegge wrote on 2020-03-25, 17:00:

Yeah, sad but true. but if it can be repaired I'll have a nice 286 machine to play with. I bought it as a package with the original keyboard and the monitor it was sold withwhen new, even got the box for the monitor.

I recognize that board design. The board that I once had got was a quality design. I have hopes that yours can be fixed.
Just do yourself a favour and don't rush things. Take a break for one or two days and try again.
Maybe there's a chart floating around on the web that gives more information on that error code.

Edit: If you can, also try to carefully re-seat all the socketed chips. Maybe there's a contact issue because of corrosion etc.
I had encountered a similar issue with another vintage device (AEA PK-232 Multimode TNC).

"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

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Reply 17 of 42, by computerguy08

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A good approach to this problem is to go step by step with the Supersoft ROM or something similar. Did you find out what does the beeping mean (in the video)?

Also, do you have the posibility to use a CGA card ? I don't think the Supersoft ROM is compatible with VGA cards.

Jo22 wrote on 2020-03-26, 00:58:

If you can, also try to carefully re-seat all the socketed chips. Maybe there's a contact issue because of corrosion etc.

I think he already mentioned that a few times 😀

Reply 18 of 42, by Vegge

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Deunan wrote on 2020-03-25, 23:20:
Vegge wrote on 2020-03-25, 17:00:

Only 00FF. The LED for ready is lit but not as bright as with the supersoft roms.
I dumped both bioses if it helps.

Checksum is correct so the image is good, but since it dies so soon I'd expect a problem with reading it by CPU. Possibly a cold or cracked solder on the sockets? Worth checking out. It's a nice mobo, a bit of in-between XT and AT. I'd say it can be repaired with some patience unlike the later 286 mobos that are ASIC based so if one of these goes bad it's end of the line. Though frankly these rarely die.

Did you try a manual reset (via a button) after power-on, in case it's a problem with voltates rising too slow?

I just checked. All connections between the bios chips and cpu are fine. They jump however over several ICs which I guess can mess it up. If they are a potential problem, can they be measured in ciruit or do they have to come off?
Yes, I have tried reset. Both short resets and longer just in case.

computerguy08 wrote on 2020-03-26, 08:59:

A good approach to this problem is to go step by step with the Supersoft ROM or something similar. Did you find out what does the beeping mean (in the video)?

Also, do you have the posibility to use a CGA card ? I don't think the Supersoft ROM is compatible with VGA cards.

That was my plan, but it didn't go very far. The beeps seems to point to "Cpu registers and logic" and some dma errors. I have a NOS cga in box somewhere, but breaking the seal just for this, I'll think about it 😉. Right now I have an EGA card there. I'll ask some friends if anyone have a CGA card for me that's not in a box.

Reply 19 of 42, by computerguy08

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This is quoted from minuszerodegrees website:

These diagnostics primarily require a CGA or MDA/MGA video card (although, strangely, an IBM MDA card does not work for the 517 […]
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These diagnostics primarily require a CGA or MDA/MGA video card (although, strangely, an IBM MDA card does not work for the 5170 version of the ROM).
EGA cards will work, but poorly.
Only some VGA cards are expected to work (more information here).
If you do not have a suitable video card, you will be forced to rely on error beeps that the diagnostics send to the speaker. See 'Speaker' section below.

So, this ROM is mainly designed around CGA and monochrome cards. If I were you, I would eliminate all possible failure points (and use fully compatible cards with said ROM).

About the seal break, I admit it's a tough one. It's up to you if you want to use that card (unless you get another one). I would use that card (this is just my opinion ofc).

I think you already visited the Supersoft manual, but just in case you didn't, here it is.

Here is what you need for beep codes (from manual), in the video it corresponds to 6 HI/Lo 1 Short , which is unable to init video.

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