VOGONS


First post, by gca

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Does anyone have a motherboard manual for the AMBRA Sprinta 386SX? NOT the 486 model (which is all I can find any detail about on-line and those details are pretty thin on the ground) it is most definitely a 386.

What I am looking for is a reference guide as to what purpose each jumper serves as none of them are labelled and I need to disable the on-board VGA controller because it failed and from what I can tell I have to disable it before an external one will function.

Additional details that might help (or hinder)...

Model: Ambra (ICPI Ltd?) Sprinta (AMD-386SX)

DOM: 11/1992

Motherboard: Rev B. 2225

Part Number of Machine: AMA2100 according to a label on the base of the chassis (which is stuck over another label marked AMA1100).

Thanks greatly in advance to anyone who can provide any information/assistance.

..........

In case anyone is wondering why I think the onboard video is dead:

Pulled out a fully functional machine (well, it was when I put it in the cupboard) and powered it up to find it totally catatonic (no beeps, messages or anything).
Checked PSU output and visually checked for bad caps, all good on both fronts.
Pulled expansion cards (NIC & Sound) … still dead.
Disconnected drives ... still dead.
Pulled memory … BEEP CODES FOR BAD MEMORY (yay, it IS still alive, kind of (thank $deity for that).
Put memory back in … dead (many bad words).

Seen similar symptoms before and each time it was down to a dead display. Feel free to disagree, I’m open to other suggestions.

Fumbled about trying to work out how to disable the bloody on-board graphics without a reference guide. After a bit of messing about swapping jumpers around (you know, switch one.. nope not it.. put it back and try the next one (yes I KNOW it’s a bad idea to do that)) I did manage to get an external card to work but the machine is now moaning about a bad fixed disk controller. So, I assume I’ve caused a conflict between components thus allowing the external VGA to function but, as I say, without a reference as to what jumper does what your guess is as good as mine.

Seeing how I had a semi-working system I ran every diagnostic software tool at my disposal on it and they all say everything is good?!?

Reply 1 of 9, by gca

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Update:

Removed the ISA VGA card I was using, pulled the VGA BIOS out of the motherboard (socketed thank goodness), reset all the jumpers back to their original positions and the machine does start to POST again but (obviously) I cannot see anything on screen and its beeping its little buzzer off in protest. So its starting to look more and more like the VGA BIOS ROM has failed causing the box to stall out during POST. Not surprised as such, according to the parts data sheet that type of ROM only has a 10 year life span (projected) and its been in there WAY longer than that.

So, yes I am still on the hunt for the manual mentioned above and the image file for the original VGA ROM (I will start hunting one down myself after I post this). The VGA ROM is labelled VGA BIOS CS7100 and is connected to a WD 90C11-LR VGA chip.

Again, as always, thanks in advance to anyone who can help.

Reply 2 of 9, by Capsndave

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I have a nearly new unit in original packaging. It should still have all original manuals. It's been boxed up for over 25 years and I was thinking of getting it out to see if it still runs. Are you still interested if I'm able to find anything that might be useful?

Reply 3 of 9, by gca

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Capsndave wrote on 2020-03-04, 12:00:

I have a nearly new unit in original packaging. It should still have all original manuals. It's been boxed up for over 25 years and I was thinking of getting it out to see if it still runs. Are you still interested if I'm able to find anything that might be useful?

Yeah if you do still have the manuals all I really need is details on what the jumpers on the board are for because none of them are labelled as to their purpose.

I did track down the fault with mine which was a trace that had been killed by the battery (at the time of the original post my only DMM didn't have continuity mode so I couldn't check for that).

Oh, and if you have the original install media (I think it shipped with MS-DOS 5 and Win3.1) then images would be interesting to have if possible.

Image of my board attached in case they are different models.

Thanks for the offer of help, much appreciated.

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Reply 4 of 9, by Capsndave

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Hi GCA. Sorry I haven’t been back to Vogons since the beginning of lock-down and have only just read your response. I’m busy again of course but I’ll find time to dig out these details for you and send on what I have. B/w Dave

Reply 5 of 9, by Horun

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Wow if you stored it for 25 years with that barrel battery it is probably corroded beyond repair. You both need to cut that battery out before it is too late.

Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor.

Reply 7 of 9, by gca

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Capsndave wrote on 2020-08-13, 20:33:

Hi GCA. Sorry I haven’t been back to Vogons since the beginning of lock-down and have only just read your response. I’m busy again of course but I’ll find time to dig out these details for you and send on what I have. B/w Dave

No rush, I know how it is right now with lock down and other Covid related restrictions.

And, to echo what Horun was saying, if you haven't already removed that battery I would as soon as possible. I wish I had sooner, caught mine just in time but I still have some bad vias to patch to get the thing back up and running correctly.

Reply 8 of 9, by Capsndave

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Hi GCA,

Apologies it has been a very long time, but I finally got around to opening the boxes of the Ambra 386 sx that I have had in my garage. Unfortunately the manual is not there . but I don't recall seeing a manual since my mother got this PC in 1992. She died in 1993 and the PC went into storage. The manual could be in a box of stuff or even at my sisters If I come across it I ill let you know .

Btw. I tried to start the PC a few weeks ago and unfortunately it went Flash-Bang, which is a real shame because it worked fine about 10 years or so ago. I had a close look and discovered a battery leak and some track damage. I'm not sure yet if this is the cause or if the board is dead, but it likely is. However the dramatic explosion occurred further up the board and in the power supply . The capacitor at C25, on board near the power connector has blown and the first capacitor adjacent to the mains input in the power supply (not the big ones) has completely blown apart. I think those two things can be fixed, but I'm not sure about additional board problems from the leaky Varta cell. The motherboard is exactly the same as your photo and I've been desperately searching for another. Needless to say I can't find one.

I'm very keen to get this PC running again for sentimental reasons and because it's otherwise in great condition. I have been doing lots of searches and a little research to see which boards might fit and if I can I'd like to pick a few brains if I have to give up on finding a direct replacement.

By the way there is a 486 variant from Ambra in the same box which appears to be the same format that could potentially provide a nice little upgrade. https://www.youtube.com/watch?v=sqmP0k6dK5k&t=143s

I have been looking closely at IBM PS2 Value point boards as a possible replacement and even bought a near identical mother board from a Wearns PC from ebay. https://www.ebay.co.uk/itm/324704822055

However this has two small serial ports instead of the large one and the parallel port runs from a header, so the ports don't align in the rear panel. Otherwise the components are almost all the same with just a few weeks difference on the mfr date codes.

This is where I need some advice. Should I cut the thick metal of the rear panel in the case so that there is a continuous slot from left to right to accommodate the motherboard ports? This could make it suitable to a wide variety of alternative boards using a riser card many of which come with their own back plate which would cover the hole. Not all boards riser slot occupies the same position and I'd have to make sure there is sufficient room for adjustment so that ISA cards can be put in the right position. However I don't like the idea of cutting the box and ruining the original condition of a near pristine PC.

Ideas and suggestions will be very welcome indeed!

Reply 9 of 9, by gca

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Aw well that sucks, its probably repairable if your lucky. Mine just had a few messed up vias in the battery area I still need to bodge wire my way around. With some fumbling of the jumpers I did manage to get mine to fire up with an ISA graphics card but it fails all diagnostics I ran on it. They are really nice machines (well, I think so anyway) when they are running.

While looking for info on my 386 all I ever came up with was details for the 486 variant which isn't much help. Though like you said the board would fit just fine into the 386 case by the look of it. Only problem would be finding one. There is little detail on line about these machines because the company wasn't around very long. Which is a shame, they got pretty good reviews from what I can recall.

Personally, I wouldn't cut the case. These things are hard to come by in any form let alone one which is in good condition. And if you do want to restore it for sentimental reasons later then such a mod would be irreversible so you have to consider that as well.