PDA

View Full Version : IBM 5150 Won't Boot



RadRacer203
May 18th, 2017, 10:36 AM
Just got a really good deal on a "working" IBM 5150 with a bunch of software. I just got it today, and it won't boot or display anything on the screen. I know the power supply, mda card, monitor, and the dip switches on the motherboard are all good, but it refuses to work.

Stone
May 18th, 2017, 10:49 AM
You gotta' be more specific. :-)

kgober
May 18th, 2017, 10:55 AM
If I remember correctly, an IBM 5150 should display numbers in the upper left corner of the screen as it tests the memory in the computer. After the memory test there should be a beep, then the system should try to read from the A: floppy drive.

If you are not seeing the memory test count up, confirm that the monitor is correctly connected to the MDA card, confirm that it has power (and is turned on, if your monitor has its own power switch), and confirm that the brightness is not set too low to see anything.

If after a while of seeing nothing, the computer beeps and tries to access the A: drive, the system is working but you just have some kind of display problem. If the computer never makes any noise and never tries to access the floppy, it has a more basic problem. If the machine was shipped to you, you may need to remove the cover and make sure nothing inside has come lose (chips working their way out of sockets, adapter cards working their way out of slots, cables loose, etc.).

And I know this sounds obvious, but make sure the power cords you are using are actually good, and the outlet you're plugging into is actually live (not turned off via a wall switch or not working due to a blown circuit breaker).

-ken

Malc
May 18th, 2017, 11:23 AM
Just got a really good deal on a "working" IBM 5150 with a bunch of software. I just got it today, and it won't boot or display anything on the screen. I know the power supply, mda card, monitor, and the dip switches on the motherboard are all good, but it refuses to work.

How do you know the PSU is good, Have you measured the output voltages, A good place to start is on Modem7's site [ Here (http://www.minuszerodegrees.net/5150_5160/MDC/minimum_diag_config.htm) ] if you haven't already.

Malc
May 18th, 2017, 11:27 AM
If I remember correctly, an IBM 5150 should display numbers in the upper left corner of the screen as it tests the memory in the computer.

Not on the 5150, Does on the 5160 though.

vwestlife
May 18th, 2017, 12:00 PM
On a 5150 PC all you get during POST (Power-On Self Test) is a blinking cursor. And "after a while" can be up to about 45 seconds on a 640K system.

RadRacer203
May 18th, 2017, 12:08 PM
I'm getting nothing on the screen with either cga or mda, no beeps, and I'm using a known good power supply in place of the original. All I get is the psu fan spinning up then nothing

RadRacer203
May 18th, 2017, 12:17 PM
When I'm using the cga monitor and card, the screen flashes black for a second like it wants to boot but can't.

RadRacer203
May 18th, 2017, 12:28 PM
It does that with all the 3 power supplies I've tried, but with this last one I hear a soft click when the screen flashes.

Stone
May 18th, 2017, 12:29 PM
All I get is the psu fan spinning up then nothingDoes that mean that after the fan spins it stops spinning shortly thereafter or that's the last sign of life?

RadRacer203
May 18th, 2017, 12:32 PM
The fan on the original power supply keeps spinning, but on the other 2 it moves about a quarter turn and stops

Stone
May 18th, 2017, 12:41 PM
If the original PSU has an AC fan and the other two have DC fans then it sounds like a short on the motherboard.

Try pulling P8 out of the motherboard and see what happens when you start it up.

Malc
May 18th, 2017, 12:43 PM
Sounds like there is a short somewhere, Follow the minimum diagnostics procedure on the link i posted, What Motherboard is it 16 - 64Kb or 64 -256Kb

RadRacer203
May 18th, 2017, 12:47 PM
I tried unplugging P8 and the screen didn't even flash. I believe it's the 16-64k board

Malc
May 18th, 2017, 12:57 PM
If it is the 16 - 64Kb board the -5V is required otherwise the board will appear dead, I assume these power supplies do have the required -5V, It will also appear dead if there is a bad ram in bank 0 IIRC, I'd check for shorts first though.

RadRacer203
May 18th, 2017, 01:30 PM
Is there somewhere I can send it out to for diagnostics? I can't do testing for shorts myself. I just don't have the tools or knowledge. I'll definitely try swapping some ram around though

RadRacer203
May 18th, 2017, 03:19 PM
Do you think that oven trick might work to help flow the solder?

Trixter
May 18th, 2017, 06:01 PM
No, don't do that. Start here: http://www.minuszerodegrees.net/5150_5160/MDC/minimum_diag_config.htm
Follow that and see how far you get.

RadRacer203
May 18th, 2017, 06:03 PM
The lady that shipped it to me sent me a picture of it working before it left, so I'm leaning towards it being jostled around in shipping and maybe not having the best solder connections

RadRacer203
May 18th, 2017, 06:22 PM
According to that website, I have some bad caps. This is the page I ended up at:
http://www.minuszerodegrees.net/5150_5160/MDC/tantalum_short_minus_5volts.htm
Is there anyone that can replace them and maybe the other cap for me? I've got the soldering skills of a gorilla...

RadRacer203
May 18th, 2017, 06:26 PM
And testing with my 5160 power supply suggests bad caps on the 12v circuit as well

modem7
May 19th, 2017, 02:25 AM
The lady that shipped it to me sent me a picture of it working before it left, so I'm leaning towards it being jostled around in shipping and maybe not having the best solder connections
A short-circuited tantalum capacitor can certainly explain why the seller showed you a photo of the 5150 working. They tend to fail at power-on time, or shortly after. One may have failed "on your watch".


I believe it's the 16-64k board
This is important (for you and us) to definitely know, for a few reasons. See [here (http://minuszerodegrees.net/5150/motherboard/5150_motherboard_revisions.htm)] then report back.


According to that website, I have some bad caps. This is the page I ended up at:
http://www.minuszerodegrees.net/5150_5160/MDC/tantalum_short_minus_5volts.htm
If you look at the web page at [here (http://minuszerodegrees.net/vcf_motherboard_failure_history.htm)], there is only one reported case of a failed tantalum capacitor on a 5V line in 5150.
It does happen, but is very rare.
Were you confident in your use of a multimeter for the resistance measurements ?


And testing with my 5160 power supply suggests bad caps on the 12v circuit as well
Per the web page that I pointed to earlier, your "suggests bad caps on the 12v circuit" is much much more likely, although it is probably only one capacitor.

Because we do not know whether you have a 16KB-64KB or 64KB-256KB motherboard, the count of capacitors on the +12V line is not known yet.

But both the 16KB-64KB and 64KB-256KB motherboards have only one capacitor on the -12V line, and that capacitor is not required for motherboard operation. How about you get a pair of cutters and cut the capacitor off the motherboard and then see if the motherboard powers up. The subject capacitor is pictured at [here (http://minuszerodegrees.net/5150/misc/5150_12volt_caps_minus.jpg)].

RadRacer203
May 19th, 2017, 04:17 AM
I just double checked and my motherboard is the 16-64k version. I'll try cutting off that one, but I think my friend is going to replace them all for me.

RadRacer203
May 19th, 2017, 04:26 PM
Well, I found at least one bad cap! I cut the one off, and it showed a little more life, but then I tried turning it on again and the c6 on bank one of the ram exploded... Is there any difference between the types of capacitors aside from that shape as long as they're the same value?

modem7
May 19th, 2017, 09:09 PM
Well, I found at least one bad cap! I cut the one off, and it showed a little more life,
With the short circuited cap removed, the power supply was then able to start up.


... but then I tried turning it on again and the c6 on bank one of the ram exploded.
Hopefully the last one to fail.

That C6 sits on the +12V line, and supports the RAM. It should be replaced, otherwise 'flaky' RAM operation may result. But for now, cut it off and see what happens.
If you are not wearing eye protection, then maybe you should.


Is there any difference between the types of capacitors aside from that shape as long as they're the same value?
On the 16KB-64KB motherboard, all of the many C6 and many C7 are two-legged tantalums and are of the same value, 10uF 16V
Photo at here (http://minuszerodegrees.net/failure/5150_16K_64K_tantalum_example.jpg).
Substituting something somewhat larger, in either (or both) capacitance or voltage, should not be a problem.
And you could use an aluminium electrolytic instead of tantalum, but I expect that most people on these forums would choose a tantalum to maintain the look.

RadRacer203
May 20th, 2017, 03:51 AM
Even with the cap on the 12v line cut off like you said, it still didn't start up, the screen just flashed black for about a second instead of a half second. Is there any difference in reliability between the tantalum or aluminum electrolytic caps? I think that might be the deciding factor

modem7
May 20th, 2017, 06:06 PM
Is there any difference in reliability between the tantalum or aluminum electrolytic caps? I think that might be the deciding factor
Tantalum capacitors normally do not fail at the rate that you are presently experiencing. If they did, no one would use them. What you are experiencing is typical of a 5150 that has not been powered on in many years. These tantalum capacitors are very old, and it appears that some old tantalums age poorly. Some people just have one cap fail, some have two, some have more. Once all of the the tantalums that are going to fail have failed, that is it. Although there is a 'school of thought' that you will need to power up your 5150 at least yearly in order to keep the tantalums 'happy'.

BTW. The other component that ages poorly, and makes frequent appearances on these forums, is the RIFA made line suppression capacitor/s in the power supply, shown at [here (http://minuszerodegrees.net/failure.htm)].


Even with the cap on the 12v line cut off like you said, it still didn't start up, the screen just flashed black for about a second instead of a half second.
So, progress. Time to go through the Minimum Diagnostic Configuration process again.

If you get to the part where you need to make resistance measurements, and you only have an analogue meter, then make sure that you select a low resistance range.