Need help identifying PC

[int 21h]

Never even thought of doing that... thanks! Yeah, delighted the PSU is working.. doesn't look like replacements are cheap!
Turns out the system is a 386..
Few interesting cards in it actually o0

That memory board is an AST RAMvantage RAMV-128
Those arn't all the cards; the rest *seem* to be generic serial or hard drive/floppy cards

 

[int 21h]

Few oddities (or are they?)
The EGA/VGA ISA card's 5v+ line had fluctuating ohms (0.07-0.1, it won't stay still for a second on pin 3, then on pin 29 it's 0.01-0.15...)
The Zenith board's 12v gives a resistance, whereas all the other ones do not seem to on pin 7 and 9.
The hard drive/floppy drive card has fluctuating resistance too on pins 3 and 29.
I used pin 1 as gnd. All 3 of these cards are in sequence [HDD,EGA/VGA,Zenith System Card?] then unaffected I guess, 386 card, RAM Expansion 1, empty, empty, empty, AST Ram Expansion,Unknown.

 

[Chuck(G)]

On the very low resistance <1 ohm, try swapping the probes. If it's still low, there are issues.

Not everyting uses +12 or -12, so open circuits there are to be expected. Everything on the other hand, uses +5.

So populate the system, but leave the display card out and see if the system still powers up.

 

[int 21h]

I'll test that on Thursday then with the vga card out!
Sorry I should have mentioned those values were kOhms, with the pins reversed it still fluctuates wildly

 

[Chuck(G)]

If you're checking for shorts, you want to use the lowest setting on your DMM--often it's the "continuity checker" setting. The problem with higher settings is that stray signals that are picked up by the probe leads as well as your skin resistance (if you're touching the contacts) can really confuse things.

 

[int 21h]

I'v a Keithley 197 DMM but I havn't yet worked out how to use the continuity on it so I'm using a cheap €10 multimeter; it ranges from 0 (open/free flowing) circuit to 1 or 1000 (closed, non existent circuit). All cards are ranging in between 300-500 for the 5v+ pins 3 and 29. The Zenith card's 12v+ shows up at 800 and the 12- gives a closed circuit (1)

 

[Chuck(G)]

Isn't a lone (1) on most inexpensive DMMs an open circuit? (i.e. infinite resistance)

 

[int 21h]

Apologies yes, 0 for closed, 1 for open!

 

[Stone]

If you're checking for shorts, you want to use the lowest setting on your DMM--often it's the "continuity checker" setting. The problem with higher settings is that stray signals that are picked up by the probe leads as well as your skin resistance (if you're touching the contacts) can really confuse things.

The nice thing about using the continuity checker is that it squeals for a short so you never need to look at the meter while checking traces or other shorts.

 

[int 21h]

Not my crappy one
Edit: Although the Keithley makes a beep when testing ohms (in the kOhm range anyway...)

 

[Stone]

Mine's a crappy one, too. A very cheap Sperry. I guess even crappy is relative.

 

[int 21h]

Heh yes it is
I have one of these:

and one of these:

And I recently sold one of these:

It was broken though!

Any idea if the resistance across that 12v line might indicate if it's the card at fault? (assuming that it is indeed a card.. only one way to find out I guess, but that will have to wait until tomorrow

 

[Stone]

Not so fast.... Mine looks a lot like your yellow one except it ONLY does V and Ω. Nothing else!

 

[Chuck(G)]

I recognize the yellow one as the $2.99 special at Harbor Freight tools--sometimes given away (along with LED flashlights) as promo gift. Not truly horrible, but at least it's disposable. For me, one indispensible thing in a DMM is an audible continuity indication--I avoid the problem of having to shift my gaze while probing circuit for shorts. But that feature may run you $20.

At any rate, why not try the boards one at a time to see if any one is a show-stopper? You're not going to wreck anything by leaving the others out--the system just won't boot.

 

[int 21h]

$2.99? I got ripped off! €10->$13~
I ran the continuity through all of the boards on the pins (1 for GND) 3,7,9,29 and the only oddity was the Zenith board which showed a high resistance

I'll run it tomorrow morning with all cards removed, and then add one each time until the problem arises! assuming the motherboard isn't to blame here! There's very few components on the motherboard as it is, only a handful of caps and they're all (looking) OK.
Will update tomorrow!

 

[int 21h]

Hello!

Put the cards in one by one, then plugged in the disk drives (2x fdd and 1x hdd) each time I powered it on until everything was plugged in (except the fan; which has the ground on it..) Anyway it didn't short, and the leds on the Zenith card lit up, except for 3 of them. Powers up fine now, makes a beep..
Forgive the terrible images.. crappy iPhone gen1 camera..

However this hideous screen showed itself..

Those scroll upwards

 

[Chuck(G)]

Are you certain that this display is the proper one for your system? The display looks like a simple horizontal sync issue, not necessarily a problem with the system itself. Perhaps the display card is configured for the wrong type of display?

 

[int 21h]

:D
Genius! Few switch flips and we're in business! BIOS needs setting etc etc; one more issue though...
I need to set the cylinders etc for the hard drive... but the hard drive is very ambiguous...
There's a very plain label on the back, and this is all it says...
- - CYL- - HD - - BCAI
1) - - 21 - - 4 - - 18575
2) - - 89 - - 4 - - 18545
3) - - 141 - - 0 - - 11623
4) - - 151 - - 4 - - 20793
5) - - 152 - - 4 - - 20794.
put the hyphens in to make it easier to read

 

[modem7]

I need to set the cylinders etc for the hard drive... but the hard drive is very ambiguous...
There's a very plain label on the back, and this is all it says...
- - CYL- - HD - - BCAI
1) - - 21 - - 4 - - 18575
2) - - 89 - - 4 - - 18545
3) - - 141 - - 0 - - 11623
4) - - 151 - - 4 - - 20793
5) - - 152 - - 4 - - 20794.
put the hyphens in to make it easier to read

That label is there to inform the user of the known bad areas of the drive, information typically entered during a low-level format. "BCAI" is possibly an acronym for Bit Count After Index.

You should be able to establish the drive's cylinder/head/SPT count by searching the Internet with the drive's make and model number.

 

[int 21h]

That's the problem; The only thing it says on it is CORE International, their address and phone etc.. and that label which gave those values.
It has BATCH-7FN436 and PROG D S stamped on it, which isn't much good...
I removed the caddy for the drive and it shows a barcode with "4426 CI AK 7 27" with the C and A underlined.. and the 27 at the end hand written in... could be a 1 2 1 though :/