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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 17th Aug 2018, 6:46 pm   #1
Join Date: Jan 2014
Location: Oban, Scotland, UK.
Posts: 669
Default Interface card on 486 processor

I have an interface card (drives external machinery) that has a fault. The board manufacturers are no longer around and the chips (all DIP devices) have had their markings sandpapered off (grrr...).

I'm trying to identify the main controller device in a 64-pin Shrink DIP package where the only pins I can (so far) confirm are +5V on pin 43 and ground on pin 26.

When first checking the pinouts I thought I'd 'got it' when I identified data bus connections that matched up to the TMS9900 pinout but when I checked the datasheet the power pins were now where near what I've found....

I've tried the usual suspects (TMS9900, 68000 etc) but no results yet. It may even be a PIC-type device (??) but that's just me guessing....

Can anyone suggest types of device (in a 64-pin shrink DIP) that I could look up to see if I can find a match?
kellys_eye is offline  
Old 17th Aug 2018, 6:57 pm   #2
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 4,368
Default Re: Interface card on 486 processor

Pictures would be good. Someone may have a version of the same card which has not had the numbers rubbed off, if it is a general purpose I/O card.

If the main device is a microprocessor as you think it may be then I hope the card includes a discrete code memory device such as an eprom, because if not the microprocessor may have its application code buried within it. If that's the case then buying a replacement chip will not help you.

Being optimistic, I would suggest that the devices which are most likely to have failed are those which connect the card to the outside world, rather than the processor itself.
SiriusHardware is offline  
Old 18th Aug 2018, 10:31 am   #3
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Location: West London, UK.
Posts: 665
Default Re: Interface card on 486 processor

Hi Kelly, as Sirius advises, photos may help.
Include the connection socket(s) especially which one(s) connect with the external Machinery.

Advise the Machinery make, type and *FULL* model number - Why the secret?

Are you aware of any other users of said machinery, who may be able to help.

You are not the first to experience this situation with uncommon hardware.
This is why it is so important to have a stock of known good spares ready should a fault occur.
Same now for items such as Dot Matrix Printers, the (old) pc itself, etc.

Regards - Mike
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Old 19th Aug 2018, 10:22 am   #4
Join Date: May 2010
Location: Grantham, Lincolnshire, UK.
Posts: 811
Default Re: Interface card on 486 processor

The only common shrink DIP chip I can recall is the Z800?

Some Japanese manufacturers used them as well.
woodchips is offline  
Old 19th Aug 2018, 5:24 pm   #5
Join Date: Jan 2014
Location: Oban, Scotland, UK.
Posts: 669
Default Re: Interface card on 486 processor

Thanks for the feedback but the issue is now moot as the board had originally suffered a short-to-chassis (blowing the top off a bus interface chip LS245) and the main processor, whatever it is, has no activity on any pins - there are some fixed logic levels at various places but nothing 'changes' even at boot up so I'm assuming it's dead and BER.
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