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View Full Version : Compaq Portable Restoration Advice



ASM
August 17th, 2012, 05:44 PM
Hello everyone,

I recently got my hands on a ‘Compaq Portable I’, I have been looking for a few weeks and I finally found one on E-Bay.
I was hoping someone could provide some tips and advice for troubleshooting and trying to fix this machine.

When I initially brought it the owner claimed that there was no power cable and therefor had not been tested. As expected the PC itself does not boot up, I had a few power cables lying around and from the label on the side I assumed no transformer was needed (220-240V, 2 Amp). When the power switch is pressed the fan starts up immediately, other than that nothing much happens. Some videos I watched showed that the lights on the HDD & Floppy drive light up after 20 seconds or so, this does not happen with me so I am hoping that there is a fault in the PSU and not the screen. After a tough battle with the plastic cover I managed to get it open and have a brief gander over the internals, other than a loose floppy driver nothing obvious seems to be wrong, I may have missed a few spots but I will look at that tomorrow.

I am quite new to vintage computers and servicing in general; I was hoping that someone could provide some assistance on where to start and what tools I should get to do it. I have been using a dental mirror and a screwdriver set but I am sure I need more than that to identify the problem, logic tells me I need a multimeter.

Thank you for any advice on how to get this PC up and running!

Chuckster_in_Jax
August 17th, 2012, 07:24 PM
Many of our members have had to repair their Compaq Portables. The most common problem are tantalum capacitors that are shorted and keep the power supply from starting up. Do a search and you will find several threads related to repairing Compaq Portables.

ASM
August 18th, 2012, 03:45 AM
Many of our members have had to repair their Compaq Portables. The most common problem are tantalum capacitors that are shorted and keep the power supply from starting up. Do a search and you will find several threads related to repairing Compaq Portables.

Ok, thank you very much.
I will use the search feature next time.
I was not sure because the fan does start up; I guess I could look where the contacts happen on the PSU.

Chromedome45
August 18th, 2012, 04:40 AM
Yep thats what happened to mine bad Tantulum Caps. Specifically on the +12v Rail. If you have soldering skills easy to replace. If not then may have to find someone who can. Also need to remove the motherboard to do this. Not an easy task. Service Manual available here: http://www.old-computers.com/museum/docs.asp?c=547&st=1

ASM
August 18th, 2012, 04:53 AM
Yep thats what happened to mine bad Tantulum Caps. Specifically on the +12v Rail. If you have soldering skills easy to replace. If not then may have to find someone who can. Also need to remove the motherboard to do this. Not an easy task. Service Manual available here: http://www.old-computers.com/museum/docs.asp?c=547&st=1

How did you figure out which caps were not working?
I do have a few capacitors around the house; maybe I can use them if they are higher rating than the current ones.
Thanks!

Chuckster_in_Jax
August 18th, 2012, 07:13 PM
I used a multimeter to check the resistance where the power cable connects to the motherboard. Disconnect the power connector first and test at the traces on the motherboard. If it shows 0 ohms, I would suspect the tantalums that are very close to that connector. You can clip one of the leads on a tantalum and recheck the resistance to see if that eliminated the short.
Also, there is a red LED on the motherboard that will light if the board is getting power.

ASM
August 20th, 2012, 12:12 PM
I used a multimeter to check the resistance where the power cable connects to the motherboard. Disconnect the power connector first and test at the traces on the motherboard. If it shows 0 ohms, I would suspect the tantalums that are very close to that connector. You can clip one of the leads on a tantalum and recheck the resistance to see if that eliminated the short.
Also, there is a red LED on the motherboard that will light if the board is getting power.

Ah, thank you!
I was wondering what that LED was for,
I will have to check again but I so not think it was lit,
I am currently away but I will buy a multimeter while I am here,
Someone mentioned a boolean instrument but I cannot remember what it was called...
Anyway, thanks again!

Chuckster_in_Jax
August 20th, 2012, 04:40 PM
[QUOTE=ASM;238401
Someone mentioned a boolean instrument but I cannot remember what it was called...[/QUOTE]

Logic Probe.