PC Enterprises PCjr Drive controller

Hardware questions and modifications

PC Enterprises PCjr Drive controller

Postby KenG » Wed Oct 26, 2016 10:57 am

This popped up on eBay this morning and I bought it.

PC Enterprises PCJr Drive Controller allows more drives for IBM PC Jr (See attached picture)

I am thinking that this was supposed to go with an expansion chassis so the exsisting controlle would be housed in the chassis. I can't imagine using it with the top of the jr off and everything exposed. I have an extra PCjr case that I think I can modify for use as an expansion chssis, but I would probably have to build a power supply. Any information I can get on this controller and how to build an adequate power supply wuld help. I used to build replacement power supplies for Commodore 64s about 30 years ago, so I know the basics. I think it was an 18 volt transformer with a center tap. Rectify to get 9 and 18 volts DC, use two large capacitors to deripple, then 5 and 12 volt regulators and finally a couple of small deglitching capacitors. I have no idea what size the cpacitors need to be and how to get the transformer and regulators of the right side to power one or two floppy drives. Can anyone here supply a diagram and parts list?
Attachments
PCjr floppy controller.jpg
Picture of the controller
(246.6 KiB) Not downloaded yet
Enhanced PCjr with a jr-IDE (1GB DOM) and a parallel port side car with a compact flash reader and backpack 1.44mb floppy attached. Tandy video mod.
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Re: PC Enterprises PCjr Drive controller

Postby Brutman » Wed Oct 26, 2016 11:23 am

I have one but I have no instructions for it, and I have not tried to reverse engineer it to see how it works. (Yet.)

I think it behaves like an interposer - you plug it into the motherboard and then put the original drive controller in the slot on the top. So it has to be used with an expansion chassis, and it probably fits only in the PC Enterprises versions.

There is no BIOS on that card so you'll have to use jrconfig and tell the machine that it has two drives installed. I don't think you need to do to much to test the card; just another floppy drive with a separate PC style power supply should do for a quick test.
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Re: PC Enterprises PCjr Drive controller

Postby KenG » Wed Oct 26, 2016 11:37 am

Tyhanks for the quick responce Mike.

I have two spare PCjrs. One has broken keyboard and light pen ports, but works fine with the IR connection. The other works OK. I figured on using the drive and power supply from the broken one with the cards in the good one to test. If that works, I will be trying to use the case from the broken one as the expasion chassis. The problem is that I would have to remove the motherboard and cut a hole in the bottom of the case. With the mortherboard moved, the power supply won't work so I will need to build one or figure out how to fool the existing one into working without a motherboard. This still would require some adjustment to mount it and protect the unused connections from getting shorted. Probably won't have time to do more than test it until winter, but would like to have the plan all worked out. I know there are two pins on the motherboard that have to insert into the power supply for it to work. I know this becuase I missed them once when I re-installed a pwoeer supply. Would there be a way to duplicate whatever they do to get the power supply to work?
Enhanced PCjr with a jr-IDE (1GB DOM) and a parallel port side car with a compact flash reader and backpack 1.44mb floppy attached. Tandy video mod.
KenG
 
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Re: PC Enterprises PCjr Drive controller

Postby Brutman » Wed Oct 26, 2016 12:56 pm

I wouldn't bother making holes in cases. In another thread here there was a Racore/Rapport expansion unit available for adoption. As of this morning it was still available.
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Re: PC Enterprises PCjr Drive controller

Postby KenG » Wed Oct 26, 2016 1:22 pm

If it is the one I think, Chromdone##, I bought one of his jrs, a motherboard, and a keyboard. That was about all I could afford. Maybe I can figure a way to mount them side by side and fit in the case. I will see when I get it and test it. This is all moot if it doesn't work. I have/am spending way more on this hobby than I should. LOL. I shouldn't have bought the controller, but I figured it was a rare oportunity and was probably better than trying to modify one of mine. I was also thinking that if I had a case and adequate power supply it might let me use a regular hard drive with the jr-IDE if I wanted to. Which brings up a question. Does the jr-IDE support two devices in a master/slave arrangement?
Enhanced PCjr with a jr-IDE (1GB DOM) and a parallel port side car with a compact flash reader and backpack 1.44mb floppy attached. Tandy video mod.
KenG
 
Posts: 148
Joined: Sat Jul 16, 2016 5:36 pm

Re: PC Enterprises PCjr Drive controller

Postby Brutman » Wed Oct 26, 2016 1:38 pm

It might, but I haven't tested it. And given the state of the BIOS that I started with, I wouldn't put bets on it.

That might be a good winter project to work on ...
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