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Need help identifying PC

I

int 21h

Experienced Member
Joined
Feb 9, 2012
Messages
148
Location
Limerick, Ireland
Hi all
Picked up an odd one today.. It's a "Zenith datasystems" machine with (aparently) no identifying model number. Originally I thought it was an XT clone or something but there was really weird expansion ports inside and an odd layout for a motherboard. Also the CPU has the markings "MC1468AP" which is of course a Motorola, what type I have no idea...
Plugged it in and it did the usual-old-computer-plugging in thing and popped; letting out the magic black smoke! And as we all know, old computers need their magic black smoke! I'll need to locate that cap soon, I think it was inside the PSU... or very near it. It has a plethora of cards, most of which I have no idea what they do, I'll pull apart the system soon to find the cap and take photos of them then. In the mean time; does anyone know what this could be....
IMG_6360_zps10b3bef9.jpg


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IMG_6366_zps13955f98.jpg
 
That looks to be a generic Zenith clone. It's most likely a part of Zenith's Z-248 line. Mine looks very similar to this, and is a ZW-248-82. These systems are backplane computers, thus the expansion slots are bigger than the normal 16-bit slot.

Nice find! Zeniths are built to last.
 
DOS lives on!! said:
That looks to be a generic Zenith clone. It's most likely a part of Zenith's Z-248 line. Mine looks very similar to this, and is a ZW-248-82. These systems are backplane computers, thus the expansion slots are bigger than the normal 16-bit slot.

Nice find! Zeniths are built to last.
Click to expand...

Ah cool thanks!
Yeah it's ridiculously heavy! I'll keep looking to get the model but that has put me on the right track!
 
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If you can get output to a display, fire it up and press Control-Alt-Ins, which will bring up the System Monitor, which is a nice utility that I wish other machines at the time had. Not just a BIOS, but a complete debugging tool combined with diagnostics, and the system setup. The system setup will tell you exactly what model you have along with the ROM versions on the CPU card.
 
Unfortunately it won't power on, it turns on and off in about the space of half a second (one of the cards has LEDs that flash).But thanks! Once I find and replace that cap I will do that!
 
Do you have any other similar power supplies you could substitute in for the current one? If you weren't so far away, I'd send you the one out of mine.
 
I don't :-(
Parts (and computers..) are really hard to come by where I am. I'll open it up in the morning and see if I can find it
 
int 21h said:
Couldn't find the bad cap in the power supply, at a loss what to do now :confused:
Click to expand...

Leave the hard/floppy connected, but unplug the motherboard/backplane. See if the hard drive spins up.

If no soap, then reconnect the backplane/motherboard and unplug the hard drive. See if the thing stays alive then.

That Motorola chip that you mentioned isn't quite right--the MC1468 is a small (14-pin DIP) voltage regulator. Might you perhaps mean a MC146818? That would be your CMOS clock/configuration chip.
 
Ok I'll give that a shot tomorrow then! Left it in my office (where my soldering station is etc) so I won't be there until the morning; do you think it will still be safe (for the circuit of course) to power it on despite the smoke coming out of the PSU? I'll have a look at that motorola chip again and double check the number on it; if that's not the CPU then perhaps its on one of the expansion cards..
 
I'll have a look at that motorola chip again and double check the number on it; if that's not the CPU then perhaps its on one of the expansion cards..
Click to expand...

Er, yeah, it is on one of the cards. That's how 'backplane' systems work. In your pictures it looks like the CPU board is probably the fourth card from the right, and judging by the extended slots, which were usually used for early (and proprietary) implementations of a 32-bit bus, it's most likely a 386DX-based system.
 
I know you are in Ireland, but I have two of these things that will have to go very soon, so if you or anyone else needs parts, please let me know.

Thanks,
Daniel
 
Got back to this today: The hard disk gets its power from a card so I'll reassemble the PSU now and see if it powers up the floppy disks without shorting (hopefully it won't damage the psu - some more? since something in there did blow), not sure how long, or if at all the leds on the floppies will light for
 
Made a pretty amateur mistake (which I still am of course!); there's 2 plugs with exactly the same head.. but 2 ports on the same board (That takes the AC), one is for the power, the other is the switch... not sure which goes in where (J4 and SWX1)
 
Here's a hint--when I'm starting work disassembling anything, I keep an inexpensive digican with me. It helps to answer the quesiton "how do I put this thing back together?". Things that may seem obvious when you're tearing something apart may not seem so a couple of weeks down the road when you're putting things back together. I also bag hardware as I remove it to help me remember which screws/nuts/whatever went where.
 
I have a fishing tackle box where I keep all the screwed segregated; worked it out anyway.. it was obvious.. only one of the cables was long enough to reach one of the ports. I'll put it back together now.
 
OK... the power supply is powering an old hard disk I have lying about, I guess that means there must be at least another short somewhere on the board (as well as whatever gave that smoke from inside the PSU). I'll have a check on the expansion boards for caps, I left my toolkit at the office so I can't put the bolts back in place properly on the PSU until at least the 26th... can't test the board without expansion cards yet as I'll need to move the floppy disk holders etc; the motherboard power cable is very short.
 
The simple way to go about this is to test the +5, +12 and -12 edge connector lines on each card with reference to the ground line using an ohmmeter. Usually, the bad card will stand right out--and you'll know which supply line to check for shorts on the card.

At least your PSU seems to be okay.
 
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