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jltursan
August 7th, 2012, 05:04 AM
Lately I've purchased a second PCjr hoping that it would be a good source of spares to help diagnose my first "absolutely dead" first PCjr (two beeps at boot).

That's what I've found until now:

1) The new PCJr arrived in a loose packaging and the case cracked badly. The disk drive was out of their anchors....yay!
2) Firsts tests lead me to find that the internal power card was blowed; so I swapped it with the one from the "dead" first PCjr and bingo!. The new PCjr displayed the blue logo!. Seems that the shipment hasn't damaged the board, only the case. The drive is still untested tho...
3) Back to the old "beep beep" dead PCjr and with the new testing platform I found the following:
- Tons of dust and some spiders.
- Bent and shorted pins in the sidecar bus.
- Power card grounding pins too large; so they made contact with a capacitor of the power card once connected. AC shorted!. Weird, they must have been replaced by the old owner.
- Board RAM shorted; so after some tests replaced one IC and yep!, no more "beep beep" and IBM logo displayed.

Now I need to test both drives, one of them making a rough spinning sound. I'll try with ImageDisk...

So since now, the only part that remains broken is a power card. I've read in this same forum that a PC power supply can be plugged directly in the molex connector of the power card bypassing the card conversor. This way the PCjr gets +5DC & +12DC; but what happens with the -6VDC voltage?, has anyone found how the PCjr works without it?. Is there any way to replace the power card?.

After all these repairing sessions, I've plans to upgrade a bit my working machine (plain 128K expanded machine); so, has anyone other hardware like joysticks, sidecar RAM o CPU boards?. Software is also welcome, I only have Cartridge BASIC and a pair of cartridge games.

mikey99
August 7th, 2012, 05:11 AM
You definitely want to clean and lubricate the rails on those diskette drives. I had a PCjr
at one time and it was necessary to clean and lubricate the rails about once a month to
keep things running smoothly. Use alcohol for cleaning the rails followed by a very light
application of silicone applied with a Q-tip.

mbbrutman
August 7th, 2012, 05:21 AM
Congratulations! I suspect a PCjr is an unusual computer in Spain.

I assume that you have seen these pages and the related PCjr web forum:


http://www.brutman.com/PCjr

As with any new machine, carefully inspect the boards and pins for damage before powering them on. Mildly bent pins can be bent back into shape. Badly bent pins might need to be cut out and replaced, which is difficult on a PCjr because many of the pins are on "Berg" style connectors that have a right angle in them.

Clean and lubricate the drive rails - that will make a world of difference. You also need to clean the heads and eliminate any loose dust in the system so that the heads do not get contaminated again. I have a scan of documentation on the cleaning procedure that I can find and send you. It's also been discussed here and on that forum many times before. (Be careful with Q-tips on the drive heads - a cleaning diskette is much safer.)

The machine can run DOS 2.1 through DOS 6.3, and possibly even later versions of DOS. Anything above DOS 4 needs to be patched; the patching procedure is in the PCjr forum.

And take a look at the jrIDE project - it is a sidecar that includes 512K (actually more) of additional RAM, an IDE interface, a clock/calendar, and a POST display. That one sidecar takes care of lots of problems.


Mike

lucasdaytona
August 7th, 2012, 07:43 AM
I have a scan of documentation on the cleaning procedure that I can find and send you.

Hey Mike, could you put that on your site? Would be very useful.

Thanks.

Lucas

jltursan
August 7th, 2012, 11:51 AM
Well, first tests after the cleaning with a dumped PC-DOS 2.1 image haven't been sucessful. After formatting it to 180K and write the image with FDimage, the diskette (DDDS used) can be read with my tweener; but it spins and do nothing when booting the PCjr. As I'm writing it with a HD drive, it's an expected result :(
I've older machines like a Tandy 1000EX; so I'll try to format a disk with these older drives and the dump the image with the HD drive. Also I can try creating a DOS 3.3 boot disk with the Tandy from scratch.

Funny that I haven't been able to access the disk from Cartridge BASIC, neither FILES nor LOAD or SAVE commands seems to work with drive, only cassette. Drive only shows signs of life when booting. I'm missing something obvious for sure...:confused:


Congratulations! I suspect a PCjr is an unusual computer in Spain.

You can bet!. Its 5160 brother is extremely popular (duh!); but PCjr was specially ill-fated here in Spain.


I assume that you have seen these pages and the related PCjr web forum:

http://www.brutman.com/PCjr

Yep, I've been lately exploring the deeps of your excellent site. Thanks for keeping such information available!


Hey Mike, could you put that on your site? Would be very useful.

Agreed!. I'm also curious about the missing "Appendix B" from the reference, is it available somewhere?

mbbrutman
August 7th, 2012, 07:41 PM
Try this:

http://brutman.com/PCjr/Eugene_Club_Docs/Care_and_Cleaning.pdf

Also, no version of BASIC can access the diskette drive if you did not boot DOS first. If the machine did not boot from a DOS diskette, then BASIC can't touch the diskette drive. (Well, not without extraordinary measures ...)


Mike

modem7
August 7th, 2012, 11:53 PM
I'm also curious about the missing "Appendix B" from the reference, is it available somewhere?
See http://www.minuszerodegrees.net/manuals/ibm_4860_tr.htm

jltursan
August 8th, 2012, 04:30 AM
Great, thanks!. Now I see that the wrong labelled pin carries -12VDC not -6VDC. I suposse that I can fit a PC power supply inside the case, don't like the idea; but I don't know how to get the -12V easily.


And take a look at the jrIDE project - it is a sidecar that includes 512K (actually more) of additional RAM, an IDE interface, a clock/calendar, and a POST display. That one sidecar takes care of lots of problems.

As far as I've seen, seems a great add-on, it has all I'm in need now. I'll peek for more info about it...