misterblack
Experienced Member
Hey guys -- a viewer sent me a very nice memory sidecar for my PCjr. He sent a Tecmar jrWave expansion sidecar.
Pics and some info:
https://imgur.com/a/m5uee6M
He wasn't sure if it worked at all as he had had it a long time and no longer has a PCjr. He also didn't have the manuals or power supply for the board.
Taking it apart, I found the AC input is rectified and converted to 5v by a simple 7805 voltage regulator. I fed the board with 5v from the PicoATX that runs my PCjr to power up the board. This board is populated with two banks of 8 by 256k RAM chips (total of 512k) and then two banks of 8 x 64k chips (for a total of 128k in these banks) bringing it to a total of 640k on the sidecar.
Upon power-up, it wasn't working correctly with the PCjr either counting to 160k then giving an "ERROR A" or it just wouldn't count RAM at all. I fiddled with the board a little and pushed the chips down and suddenly it's counting to 640k and seemingly working normally.
I was wondering if anyone knew anything about this board? Is 640k the max capacity of it? I can't find any scans of the manual for it. It seems to have the expansion connector on it for the jrCadet (expansion board) but reading the manual for the jrCaptain, that was only populated with banks of 64k RAM.
The switch settings for the 640k configuration are like this:
1234
COOO
(C = closed, O = open as marked on my switch block. These are rocker switches so switch 1 is down, others are up)
12345678
11111111
(1 = ON, 0 = off -- so essentially this block is entirely ON. All switches down)
Pics and some info:
https://imgur.com/a/m5uee6M
He wasn't sure if it worked at all as he had had it a long time and no longer has a PCjr. He also didn't have the manuals or power supply for the board.
Taking it apart, I found the AC input is rectified and converted to 5v by a simple 7805 voltage regulator. I fed the board with 5v from the PicoATX that runs my PCjr to power up the board. This board is populated with two banks of 8 by 256k RAM chips (total of 512k) and then two banks of 8 x 64k chips (for a total of 128k in these banks) bringing it to a total of 640k on the sidecar.
Upon power-up, it wasn't working correctly with the PCjr either counting to 160k then giving an "ERROR A" or it just wouldn't count RAM at all. I fiddled with the board a little and pushed the chips down and suddenly it's counting to 640k and seemingly working normally.
I was wondering if anyone knew anything about this board? Is 640k the max capacity of it? I can't find any scans of the manual for it. It seems to have the expansion connector on it for the jrCadet (expansion board) but reading the manual for the jrCaptain, that was only populated with banks of 64k RAM.
The switch settings for the 640k configuration are like this:
1234
COOO
(C = closed, O = open as marked on my switch block. These are rocker switches so switch 1 is down, others are up)
12345678
11111111
(1 = ON, 0 = off -- so essentially this block is entirely ON. All switches down)