• Please review our updated Terms and Rules here

Need help with my old IBM XT 5160

Druid6900 said:
Buy a P.O.S.T. card from China on feEbay for 12 bucks US, including shipping (the kind with the PCI AND ISA edge connectors).

In about 95% of the case when I use one of mine, it pinpoints the fault accurately.

It's just so much easier than buying/dragging out a scope, logic analyzer, what-have-you.

I agree that a logic probe is a handy device, especially if you have the SAM'S Computer Facts book for your computer which shows you what the logic states should be on every chip on the board in a known point in the startup sequence (usually just turned on).

However, if you're not lucky enough to have the SAM'S book, a logic probe alone may not be of much help, since, just because a pin is high or low, doesn't mean it's SUPPOSED to be high or low. This is where a signal injector comes in handy along with the logic probe. You can inject the input of a gate and see if the output is doing the righ t thing.
Click to expand...

If this is a stone-dead 5160 (doesn't even start to execute anything), a POST card isn't going to tell you a thing--except what you already know--that it's dead.

A logic probe isn't useful so much for high-or-low indication, but for indicating that something is going on on a line (pulse indicator). If you put the thing on any of the address/data lines and get a steady high or low, you know to begin checking the other lines (reset in, clock, etc.).

I've never used the Sam's stuff since I quit working on TV sets. The techref will give you the schematic--and you can figure out the rest from that.

Wonder why no one makes a clone of the old HP Logic Dart? I'd think that one could be made fairly cheaply today--far less than the king's ransom a used one commands.
 
Port 60H versus port 80H

Port 60H versus port 80H

patscc said:
That's a great idea, but I thought XT's only wrote 5 codes to port 60h ?

00 or FF CPU register test failed
01 BIOS ROM checksum failed
02 System timer 1 failed
03 8237 DMA register Read/Write failed
04 Base 32K RAM failed

I must be getting something confused.
Click to expand...
Yes, the IBM BIOS in a 5160 outputs POST codes to port 60H (a keyboard port). For others, why patscc might be confused is because POST cards generally monitor port 80H, the diagnostic port used in the 5170, not port 60H. Some POST cards can be switched to use other ports, e.g. port 84H for Compaqs, but I've yet to see a POST card that can monitor port 60H. Does anyone have a card that can monitor port 60H ?
 
elton121,

Something worth trying is to remove all of the socketed RAM ICs (using static safe procedures), just in case one of those RAM chips has failed in a way that stops the motherboard.

It sounds like you don't have access to another 8088 CPU. You could buy a replacement, but from personal experience and from what I've read, the 8088 is quite reliable.

On two 'unresponsive' 5150 motherboards (very similar to the 5160) that I've fixed so far, one had a bad ROM and the other had a bad RAM chip in the soldered-in row. Of course, there are many other reasons for failure.

ROM failure is fairly common across all kinds of old computer equipment, and it is certainly within your ability to replace the ROM BIOS ICs (U18 and U19 in a 5160) if you can get a replacement set.
If you know someone who can burn EPROMs, we can direct you to web sites where that someone can get the data to be burned into the EPROMs. If not, someone here (including myself) can send you a set of EPROMs, but there will be the cost of the EPROMs themselves plus international postage, and you will be taking a chance.
Perhaps it is better to purchase a known working motherboard.
 
Can't read

Can't read

modem7 said...Already done (post #18 )
Click to expand...
Darn. And I'd gone back and re-read all the posts. Must have missed that bit, right at the end of the post. It even says orange.
Hope it didn't cause any confusion.
It would still be interesting to know what when the last time it was turned on was.
patscc
 
I don't normally do this but he already has a multimeter right? Could he check chips by checking for voltage on pin 1 of any ICs he's seeing? He might find a bad IC that way, even if you can't identify pin-1 (usually a marker in that corner or bottom of chip telling you pin 1 would be in that corner). http://www.nteinc.com/faqs/IC_Pin1_Chart.pdf, not 100% and it's just for them but atleast that helps a little on how to guess where the voltage pin would be.

I'm just trying to think of things he could test that might determine replaceable parts vs buying another 5160.
 
barythrin said:
I don't normally do this but he already has a multimeter right? Could he check chips by checking for voltage on pin 1 of any ICs he's seeing? He might find a bad IC that way, even if you can't identify pin-1 (usually a marker in that corner or bottom of chip telling you pin 1 would be in that corner).
Click to expand...
No. It's not that simple.

patscc said:
Darn. And I'd gone back and re-read all the posts.
Click to expand...
Yeah. I've done that myself a few times, always when I'm in a hurry.
 
Voltage check

Voltage check

I could have sworn I posted this a few hours ago, but I don't know what happened to it, so I'll post a condensed version of it.

With power off.
Hook the black lead of the multimeter to ground.
Locate pin 16 of the co-processor socket (socket next to 8088, pin 1 upper left, pin 40 upper right), and put the red lead tip on the hole.
Set your DVM to AC.
It should read 0.
Power on the XT, and watch the meter. After a brief spike, it should settle to about 2.26 VAC while the system bus is operating normally. If it suddenly drops, the bus might have locked. In this case, if you measure DC at pin 16, you might see something near 0 or something near 5 volts.
I tried it with the 8088 running, got 2.26 Vrms, with the 8088 out, I get 0.

Pin 16 connects AD0, which is a very busy pin, as it's AD0 of the multiplexed address/data bus. The pulstrain is rapid, fairly constat, and even though the pulses vary from 0 to 5 volts, but the AC meter averges this out, and you should get a twitchy 2.26 VAC.

I'll post back if I think of something useful, but first I gotta fix my keyboard.

patsc
 
Hi

Thanks for your help so far! I'm a little bit busy at the time so I cannnot really try anything for now but I will do so at the weekend ;)

For the time being I've took some pictures for you to see what I have. I don't know if they are helpful but perhaps you can also describe on them what I can do. :)

So here are the pictures:






 
elton121 said:
dsc02231ac8.th.jpg

dsc02232po0.th.jpg

dsc02238uo6.th.jpg
Click to expand...

I have never seen the Spare socket in use... Was there something in the socket closest to the Powersuply?
 
You must log in or register to reply here.
Back
Top