• Please review our updated Terms and Rules here

My IBM 5150 nothing on screen and problems..

thegenerallee86

Experienced Member
Joined
Feb 1, 2021
Messages
143
Just turned on the computer for the first time and it does turn on but none of the lights come on and I do hear something running but think it is the power supply and no luck with the rgbi connector on my 1902 nothing except when I shut the computer off it does flicker so then I tried using composite and do get a sort of horizontal line that is only a 2 or 3 inches long just a little off center of the screen and it is not a solid line, but also repeats all the way up and down the screen with space in-between them?
 
You might need to measure for power. The fan is powered by AC, so it may run even if the rest of the power supply is shutting down because of an external short or internal failure.

 
Just an update I checked and opened the case and the fan is not spinning at all though it twitches once when I turn it on and all the voltages are within specs though? It is the HDD I hear spinning.
 
Just an update I checked and opened the case and the fan is not spinning at all though it twitches once when I turn it on ........
Most people here experienced with the IBM 5150, hearing only that symptom, will say to themselves, something like, "This is 'classic'. The fan in the power supply is DC powered, most likely connected to the +12V DC line. The power supply actually started, and the fan (getting DC voltage) started to turn, but within a very short period of time, the power supply then shut itself down due to a problem (internal or external). "

..... and all the voltages are within specs though? It is the HDD I hear spinning.
That is the odd bit. The hard drive spindle is powered from the +12V from the power supply. Backed up by the fact that you have measured +12V (reaching the motherboard). So why does the power supply fan start and then stop?

If the fan was AC powered, it would continue to run if the power supply shut itself down. It must be DC powered. Even if we assume a 5V powered fan, you have measured the presence of +5V (and -5V) being generated by the power supply.

A possibility is multiple problems, one being that within the power supply, the fan is powered by some circuitry that is dedicated to generating a DC voltage for the fan only, and at turn-on time, that circuitry is starting then stopping. Seems unlikely, but cannot be discounted yet.

The fan problem certainly needs to be looked into first, otherwise the power supply could overheat, damaging something.

I think the first thing to do is to confirm that you are not changing variables between the observations. The IBM 5150's stock power supply, if good, will start-then-stop if it is either inadequately loaded, or is overloaded. Confirm for us that you didn't change anything between observing the following three:
* "the fan is not spinning at all though it twitches once when I turn it on"
* The hard drive's spindle always turns, even when the power supply's fan no longer turns.
* All voltages (including POWER GOOD) are as expected, as shown at [here].
 
Most people here experienced with the IBM 5150, hearing only that symptom, will say to themselves, something like, "This is 'classic'. The fan in the power supply is DC powered, most likely connected to the +12V DC line. The power supply actually started, and the fan (getting DC voltage) started to turn, but within a very short period of time, the power supply then shut itself down due to a problem (internal or external). "


That is the odd bit. The hard drive spindle is powered from the +12V from the power supply. Backed up by the fact that you have measured +12V (reaching the motherboard). So why does the power supply fan start and then stop?

If the fan was AC powered, it would continue to run if the power supply shut itself down. It must be DC powered. Even if we assume a 5V powered fan, you have measured the presence of +5V (and -5V) being generated by the power supply.

A possibility is multiple problems, one being that within the power supply, the fan is powered by some circuitry that is dedicated to generating a DC voltage for the fan only, and at turn-on time, that circuitry is starting then stopping. Seems unlikely, but cannot be discounted yet.

The fan problem certainly needs to be looked into first, otherwise the power supply could overheat, damaging something.

I think the first thing to do is to confirm that you are not changing variables between the observations. The IBM 5150's stock power supply, if good, will start-then-stop if it is either inadequately loaded, or is overloaded. Confirm for us that you didn't change anything between observing the following three:
* "the fan is not spinning at all though it twitches once when I turn it on"
* The hard drive's spindle always turns, even when the power supply's fan no longer turns.
* All voltages (including POWER GOOD) are as expected, as shown at [here].
Definitely not changing any variables, did not remove or add anything, also do not have keyboard or Monitor connected when checking the voltages either I am not using an original IBM Monitor just a Commodore 1902 Monitor.
 
Strip it down to PSU, mainboard, and video card. Turn it on and wait a bit. Does it beep? If not, the system is not working. Try a different PSU, then a different video card. After that, you narrowed-down the broken part.

If it does work however, re-add the other parts one-by-one until it stops working - and again you narrowed-down the broken part.
 
I just stripped right down to motherboard and noticed that there might be a short on the 5V rail on the motherboard because I put my neg on ground and red on the 5v on the closest pin to the front of the case where the power plugs into the motherboard and it does beep once and goes away? Also does it on the psu too? My Motherboard is the 64KB-256KB one.
 
I just stripped right down to motherboard and noticed that there might be a short on the 5V rail on the motherboard because I put my neg on ground and red on the 5v on the closest pin to the front of the case where the power plugs into the motherboard and it does beep once and goes away? Also does it on the psu too? My Motherboard is the 64KB-256KB one.
The fact that your multimeter beeped (even if it was for a little while) suggests to me that you have your multimeter in 'continuity' mode. 'Continuity' mode is not a short-circuit finder. For example, I was to put my multimeter into continuity mode, then go measure a perfectly good 56 ohm resistor, my multimeter will beep. Why? In continuity mode, my multimeter beeps at anything less than 100 ohms. So, continuity mode needs to be thought of as a low-ohms indicator. Some things that you measure are expected to be of low ohms. If measuring resistance, you really should have your multimeter in resistance mode (and then in measuring, know roughly what to expect).

There cannot be a short-circuit on the +5V rail of your motherboard. If there was one, the typical power supply used in the IBM 5150 would shut down its outputs - you would measure no +5V at all. Earlier, you indicated that you measured +5V.
 
My Motherboard is the 64KB-256KB one.
And is the PSU the stock IBM 63W (or 63.5W) one?

Just an update I checked and opened the case and the fan is not spinning at all though it twitches once when I turn it on and all the voltages are within specs though? It is the HDD I hear spinning.
Again, that is really odd (PSU's fan not turning when all outputs are good).

Confirm for us that you did those voltage measurements whilst the motherboard was plugged into the PSU - per [here].

Does the PSU's fan spin as expected when only the HDD is plugged into it ?
 
I am pretty sure it is the PSU is dead because I tried it in my 5160XT and did the same thing, also tried all of the expansion cards in my 5160XT and they all worked, also figured out how to Low Level Format the 5150 HDD and that works as well, but tried the MB without anything except the HDD in the 5160 and still nothing on the screen, So I am pretty sure it is the PSU and MB, I think there is something wrong with the BIOS is bad or corrupted or something?
 
I am pretty sure it is the PSU is dead because I tried it in my 5160XT and did the same thing
'Dead' suggests that the PSU is not outputting voltage. Yours is, so perhaps 'faulty' is a better word to use. Measuring PSU output voltages as within tolerance, and the POWER GOOD line being a logic (TTL logic) high, is in reality a confidence check. What it doesn't do is check that the POWER GOOD line is fully behaving as expected. As shown at [here], straight after the power switch is turned on, POWER GOOD needs to be a logic low for a short period. Per note 1 at the bottom of [here], in the IBM 5150 and IBM 5160, the period needs to be at least 840 ns.

In the example at [here], it appears that the POWER GOOD signal was going high too soon after power-on, resulting in the CPU not executing the power-on self test (POST).

So I am pretty sure it is the PSU and MB, I think there is something wrong with the BIOS is bad or corrupted or something?
Regarding the IBM 5150 motherboard. The symptom of 'appears dead' can have many many possible causes. Using your known-good PSU, try the diagnostic procedure at [here].
 
Well the Motherboard is to corroded to repair I sent it to someone to fix and they said the couldn't get it to boot either, luckily I already bought another MB that works fine and have it installed now and the thing works awesome and also did a have one problem with it shutdown and wouldn't turn back on but I fixed it and had to remove the 2 capacitors as stated here: http://minuszerodegrees.net/5150_5160/MDC/no_beeps_1_1_2.htm and pic of capicitors I removed here: http://minuszerodegrees.net/5150/misc/5150_12volt_caps_plus_minus_64_256KB.jpg and the fully solved that problem with the refurbished MB and now it fully works though I still have to relube and grease the Floppy drive and check alignment when I get an alignment disk because it doesn't read all of the disks very well and have tried cleaning the heads already.
 
Back
Top