View Full Version : IBM PC 5170 "dead" on power up for the first time - help needed!

August 19th, 2017, 09:32 AM
So I bought one of the NOS (new old stock) IBM PC 5170 on eBay a while ago the ones that Clint from LGR also bought and made a Youtube video about and I first had the time to unpack it today and power it on. I live in Denmark, so I kept it at the factory 230v setting, connected a monitor to it, and crossed both my fingers... and... nothing happened, so I quickly switched it off and then on again, and this time it made a quick blink on both the LEDs and then a popping noice, and went dead.

So I am a sad person right now.

I need some help to get this beautiful AT working, but I am not a technical minded person, so hopefully someone here can guide and help me fix it. Or maybe even a person from Denmark reads this, and know what to do, so I can get fixed in person. I opened the case and just by looking I can not see anything I would dare to touch before getting adwise from an AT expert. Does the PC have a fuse somewhere, or what could be causing that awful popping noise?

August 19th, 2017, 10:09 AM
The standard 5170 power supply has a fuse. The fuse is socketed so very easy to replace. Only take undoing 4 screws IIRC. Wait a day before trying to open the power supply to let any capacitors lose charge. While you wait, look over the motherboard for any exploded or disconnected component. You don't want the new fuse to blow.

I replaced the fuse in one about 25 years ago. It was a lot easier than it looked.

August 19th, 2017, 10:54 AM
first, lucky you that you can afford that. I'd give up my legs to be able to have a NOS 5170. Now on to your issue. Just because its "new" doesn't mean that a part cannot be bad, and I'd start with the power supply. Its very possible a capacitor exploded. I don't know if you have any electronic stores near by that can solder a new one on for you but id bet money that the issue is contained within the power suppy

August 19th, 2017, 11:49 AM
My first guess is that one (or more) of the tantalum capacitors went to short and then popped which is often seen in vintage gear especially if they are not turned on for long time. These caps are often found on the motherboard and expansion cards of that era.

First, check that power supply is working or not by removing power supply cables from motherboard, floppy and harddisk drives and then connecting a modern working harddrive (purpose is to load the power supply because it may not kick in without any load) and then powering it on. If harddrive works in this test, you can assume that power supply is working and there is a short somewhere on the motherboard or on an expansion card. If you have a multimeter, you can verify the voltage levels of the rails (+12, +5, -5 and -12 V rails) too. Depending the result of this test, we can direct help to the possible fault areas, let us know the result.

As a general rule, not powering the computers and their peripherals on for very long time is not a good thing actually, except cosmetics :). It would be nice to power them on for few minutes at least per month to extend mainly the life of the capacitors and to keep hard drives of your computers from stiction away.

August 19th, 2017, 11:53 AM
I second everything pcdata76 just mentioned. It's quite easy to verify whether the PSU is faulty or not. As an alternative you could plug it into another motherboard that is known to work.

August 19th, 2017, 01:31 PM
And I third it. The overwhelming likelihood is there's a shorted tantalum capacitor. Even if the 'pop' wasn't the affected part exploding, it's easy enough to track down and replace. In my case, the two bypass capacitors on the FD/HD controller, next to the bus connector.


August 19th, 2017, 02:04 PM
Plugging into 230 VAC is always a brutal way to wake up. It just needs some TLC ... there is unlikely to be any expensive damage done. FYI, my particular AT was not equipped with a fuse.

August 20th, 2017, 04:35 AM
First of all: thanks everyone for your input and comments!
I am going to try to find a person here in Denmark, who is good at fixing old computers, and when I do, I will have him take a look at your comments first and see if helps bring it back to life. It might take some time for me to get it fixed, but when I do, I will write here again about how it went. Again, thank you all! :)