Mike's PCjr Page

DarkStar2032 wrote:Do you have specs on that AC adapter?

It’s a 9 VAC adapter but you can use any 9-12 VDC adapter since the input is immediately rectified and sent through a 5VDC regulator.

Fully loaded the jrCaptain manual says it wants 780ma.

JudgeMonroe wrote: The only thing that stands out is that the RASB signal (pin 4) is not continuous between banks though CASB (pin 15) is. I'm not sure if this is supposed to be so and I can't see evidence for either case from traces on the crowded board.

I've traced the RASB signal for both banks to the PLA at U23. Bank 0 connects to pin 19 and Bank 1 to Pin 18. This is basically the end of the line; that's not a piece I can swap out and I don't know what it does.

There are a couple of ways around the JrCaptains power supply.

1) I found this in a old PCJr newsletter from 1991 and I use a modified version of it and just run a 5 volt DC line off the same place the floppy is powered to the JrCaptain, I found this works if your powering your JR with something other than the standard short power board that most JRs had :

The fix is easy. I took a standalone 5 volt supply and attached the positive lead to the bottom leg of the Captain’s regulator chip the one bolted to the metal shield to which the parallel connector is attached and the negative lead to the shield itself. The problem is gone and the computer can be left on all day without any problems.

2) Adrian Black from Adrian's Digital Basement Just rewired the power supply input to 5 volts DC https://youtu.be/_CNruhSYC2E?t=104. His unit was a Tecmar Wave but that pretty much the same as the JrCaptain without the extra features but only a memory expansion.