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View Full Version : Help with an ibm 5150 that won't post



Teddy06550
April 6th, 2017, 08:56 AM
Hey all not sure if anyone has any knowledge on how to get these pcs working again but I can't seam to get it to post at all. I've checked power supply and all the voltages are ok and both floppy drives are fine. Nothing on the display at all but the pic speaker make a very odd noise kind off crackally sounding

thanks
Ed

SomeGuy
April 6th, 2017, 12:31 PM
not sure if anyone has any knowledge on how to get these pcs working again
There are people here who could repair those in their sleep. :D

Start with a couple of quick questions, is the power supply staying on? Have you visually inspected the motherboard and checked for shorts or damage? Have you tried removing any unneeded cards (just to get a beep). Also is this a 16k-64k board or a 64k-256k board? What is the over all physical condition of the system?

Stone
April 6th, 2017, 01:07 PM
Try removing P8 from the motherboard power connector and see if that makes any difference.


... and both floppy drives are fine.How did you determine this?

modem7
April 6th, 2017, 04:09 PM
Welcome to these forums.

Lots of IBM 5150 information at minuszerodegrees.net


... and both floppy drives are fine.
Those are not required to get a display (flashing cursor) at 5150 power-on time.


... but the pic speaker make a very odd noise kind off crackally sounding
A single click at power-on is often heard.


I've checked power supply and all the voltages are ok ...
Refer to the web page at [here (http://minuszerodegrees.net/5150_5160/MDC/no_beeps_2.htm)]. Was the 'POWER GOOD' line one of the things things that you checked? Without it, the motherboard will not start.

So, if the POWER GOOD line and the voltages are within spec, the we can deduce that:
1. Nothing is overloading the power supply.
2. Problem cause is on the motherboard.

There are lots of components on the 5150 motherboard, which if they fail, will cause the motherboard not to start. For example, a faulty RAM chip (or chips) in the first bank of RAM (soldered in) is relatively common.

But perhaps your motherboard is starting, and the problem is a display related one. If so, expect to hear a single beep from the speaker at the end of the power-on self test (POST). That could take a minute or more. And before POST end, you would see and hear activity on floppy drive A:

Have you tried the 'Minimum Diagnostic Configuration' test at [here (http://minuszerodegrees.net/5150_5160/MDC/minimum_diag_config.htm)] ?