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IBM 5170 not completing POST

M

Mr. Macintosh

Member
Joined
Oct 6, 2013
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28
Location
San Diego
Hi there!

I’m trying to diagnose an IBM 5170 revision 2 motherboard that doesn’t seem to want to boot. I get no POST beep of course, so I went and bought a POST diagnostics card. Unfortunately, the card is telling me that the computer stops at “00” or “- -“ most of the time, which I take as it not even able to begin to POST.

There was some corrosion on the RTC chip, but I traced out all the connections and removed most of the funk and everything seems to be OK there. I also went through the routine of checking all the relevant voltages from the PSU and on the RTC pins, but nothing bad seems to be coming up. Anyone know what else I can do to figure this out? I’d really like to get this machine running again. Thanks!
 
Yeah I heard about the “load resistor” thing. I still have the original hard drive in there, I just removed the controller card along with all the others to remove variables.
 
I see. Any way I can purchase a set of ROMS? Or do I have to make them myself. Also, is there perhaps a hardware debugging method to identify the damaged component? My money’s currently on the MC146818P (U117) chip simply because it had the most corrosion and has been known to stop the boot procedure, but is there any way to be sure? Thanks!
 
Mr. Macintosh said:
I see. Any way I can purchase a set of ROMS? Or do I have to make them myself.
Click to expand...
See [here] for a list of some people and companies who can produce the two ROM's for you.

Mr. Macintosh said:
My money’s currently on the MC146818P (U117) chip simply because it had the most corrosion and has been known to stop the boot procedure, but is there any way to be sure? Thanks!
Click to expand...
For the IBM-supplied BIOS in the 5170, the POST codes produced by it are at [here]. If only the MC146818P (and/or its supporting circuitry) had failed, you would have seen:
- For the 01/10/84 dated BIOS, the POST codes progress up to then stop at 02.
- For the 06/10/85 and 11/15/85 dated BIOS', the POST codes progress up to then stop at 03.
 
Mr. Macintosh said:
I’m trying to diagnose an IBM 5170 revision 2 motherboard that doesn’t seem to want to boot.
Click to expand...
The fact that you have specifically used "motherboard" rather than computer, suggests that you have proven that the motherboard is the cause of the symptoms. Is that the case ?

The distinction is important. For example, a working 5170 motherboard is not going to start if the POWER GOOD signal from the power supply is not going active.

Mr. Macintosh said:
I also went through the routine of checking all the relevant voltages from the PSU ...
Click to expand...
Did that include the POWER GOOD signal ?

(Even though the +5V/-5V/+12V/-12V are in spec, it is possible that a fault in the power supply results in no POWER GOOD signal being generated. Good to rule that out early.)

(To start, the 5170 motherboard needs only +5V and POWER GOOD.)
 
Also, have you re-seated the two BIOS ROM chips ? (And verified that they are in the correct slots, orientated correctly, and don't have bent pins.)

In your case, you do not need to re-seat the RAM chips at this time. Had they been the only problem cause (poor connection or faulty), you would have seen the codes on the POST card advance up to the point where the first 64K of RAM is tested.
 
Thank you for your input. I have checked the POWER GOOD pin, and it’s reading about 5v. I have wiggled the BIOS chips a little, but haven’t taken them fully out. I believe they are in the correct slot/orientation. I have also fully reseated the CPU. Since it’s stopping so early, I’m inclined to believe it’s something fundamental that’s wrong (sometimes the diagnostic card just stays at “ -“. If the CPU was the problem, how would you know short of swapping with a replacement? I am also going to try running the motherboard off another AT-class PSU just to rule that out, even though my measurements looked good.
 
The IBM 5170 motherboard startup sequence is:

1. Motherboard receives +5V and POWER GOOD.
2. POWER GOOD takes the motherboard out of reset. As a result, the CPU jumps to address FFFF0, an address in the BIOS ROM.
3. BIOS ROM starts its POST component.
4. A POST card will be seeing POST codes as the POST progresses through execution.

Mr. Macintosh said:
I have wiggled the BIOS chips a little, but haven’t taken them fully out. I believe they are in the correct slot/orientation.
Click to expand...
If you received the motherboard in a faulty state, then for all you know, the previous owner put in wrong BIOS ROMs, or got the sockets wrong, orientation wrong, etc.
So I think you should go beyond "believe".
Using the BIOS ROM photos at minuszerodegrees.net, you should be able to get from "believe" to "know".

Past that, the contents of the BIOS ROM's may be bad. Substitution with known good would be the way to ascertain that, however, if you get a set of Landmark/Supersoft diagnostic ROM's, and they produce output (even just beeping to the speaker), then bad BIOS ROM's become likely.

Mr. Macintosh said:
If the CPU was the problem, how would you know short of swapping with a replacement?
Click to expand...
With knowledge of the CPU ins and outs, including timings, making various parallel measurements using appropriate equipment. It's a pain. That is why I make sure I have spares of things.
 
F6CCD2DB-1C36-40AA-A3DC-170BCE53C43B.jpg

I’m fairly confident they’re in the right place/orientation. Now as to whether or not they’re corrupted, that’s a different story. I’ll try to acquire a set of Landmark ROMs, and maybe a 286 if I can.
 
What would be a good video card to use with the supersoft/landmark test roms? From the Minuszero page about them for the 5170, he states that most cards do not work with the test roms. But some must. I'd like to get a working one for future troubleshooting.
 
I also got one of those PC Analyzer cards. see picture. the manual is very minimal for IBM bios. It only mentions about beeps for IBM bios. I get no beeps, just code 02 01 on my 5170 board.
I did test the PSU with a PSU tester and it is good.
Thought suggestions
 

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KLund1 said:
What would be a good video card to use with the supersoft/landmark test roms? From the Minuszero page about them for the 5170, he states that most cards do not work with the test roms. But some must.
Click to expand...
You are paraphrasing me. Of course there are cards that work. See what is written at [here].

KLund1 said:
I also got one of those PC Analyzer cards. see picture. the manual is very minimal for IBM bios. It only mentions about beeps for IBM bios. I get no beeps, just code 02 01 on my 5170 board.
I did test the PSU with a PSU tester and it is good.
Thought suggestions
Click to expand...
Why are you hijacking this thread ? It causes confusion to old folk like me, getting confused about what post refers to what computer. If you open a new thread about your 5170 problem, I can tell you more about your particular POST card (your "PC Analyzer card"), and about the 02 01. When you do, include the revision of IBM BIOS you have.
 
After contacting one of businesses on the list by email and getting nothing back, I decided it would be an educational and possibly fun endeavor to learn to make my own ROMs. I've done a little research, and come across a "Willem" EPROM burner that I believe says it can do the 27256 chips the 5170 takes. It sells for about $30 on eBay, so it's certainly doable. Do I just buy that, a couple of EPROMs (intel D27256-1 I believe) and use the ROM images on the minuszerodegrees website? Thanks!
 
Mr. Macintosh said:
After contacting one of businesses on the list by email and getting nothing back, I decided it would be an educational and possibly fun endeavor to learn to make my own ROMs. I've done a little research, and come across a "Willem" EPROM burner that I believe says it can do the 27256 chips the 5170 takes. It sells for about $30 on eBay, so it's certainly doable. Do I just buy that, ...
Click to expand...
Be aware of what I have written about the Willem units at [here].
And I learned recently that some are not supplied with software/documentation - you are expected to source that yourself.
And you may receive a different model (a later one) to what you ordered.
I only use my Willem for old chips such as the 8742 ([here]).

Per the second last point at [here], do a Google search of these forums. The subject of buying an EPROM programmer has been discussed many times.

Mr. Macintosh said:
... a couple of EPROMs (intel D27256-1 I believe) and use the ROM images on the minuszerodegrees website? Thanks!
Click to expand...
For the IBM 5170, you can use 27256 or 27C256, as long as they are rated at rated at 250 ns (or less [faster]). Note that what you acquire may need to be erased.

I have started to use W27E257-12 as a replacement. Cheaper, and I can get my modern EPROM programmer to erase them.
 
If your shopping for a eprom/eeprom programmer a good entry level to midrange unit is the Minipro TL866. Many people on here (myself included) use them. It can't program everything; but it certainly can do the majority of things.
 
Yeah I was doing some research, and it looks like the Minipro tl866ii is the best device for what I’m doing. It also has the benefit of being able to program those W27E257 chips modem7 was talking about, which do look like a better solution than the UV EPROMS.
 
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