Mike's PCjr Page

Hi guys, wanted to share some info here that might be useful. A nice viewer sent me an "unknown working condition" Tecmar jrWave expansion sidecar for my PCjr. No manual or power supply.

Pics:
https://imgur.com/a/m5uee6M

Since I knew it needed 8v of AC sent into the sidecar, I opened it to investigate. The AC just gets rectified, filtered through a big cap and then regulated down to 5v using a simple 7805 voltage regulator. I just clipped on a 5v feed from my PicoATX supply inside the PCjr to test. The board was populated with two banks of 8x256k chips and two banks of 8x64k chips. Total of 640k. The DIP switch settings are unknown to me as there was no included documentation and I can't find any information online for this card. I hoped the existing switch settings were correct (you can see them in the photograph.)

Upon the first boot, I either got 160k and ERROR A -- or just no memory count at all. I fiddled with the board by pushing down chips and now it's working to 640k! I'll probably remove every socketed chip and spray some deoxit in the socket before reseating the chip. (If it continues to by flaky.)

Other info: It's drawing about 400ma at 5v with this RAM configuration. I would be very shocked if the PCjr itself can't supply that much current through the side connector (now I have a 160w microATX power supply in it) .. but I guess I'll just run a cable out the modem jack over to the card.

Anyway, if anyone has info on the switch configuration, max memory configuration and compatibility information with the jrCadet, let me know. (It seems to have the jrCadet connector on it.)

-Adrian

The only info I have found is here https://www.brutman.com/PCjr/docs/Tecma ... n_v1.3.pdf.

The jrWave looks fairly close to a jrCaptain without the Real time clock and parallel port. The wave does seem to have those extra 4 dip switches that the captain does not. I have seen the Techmar treasure chest software floating around but cant recall where off hand right now. Even though you got it working the jrCaptain thread a few threads down has a link to the newsletter with the 5 volt mod you already figured out.

Heres another interesting link http://etc.pixesthesia.com/jrstuff/Techmar05.pdf



*side note* I have the Techmar Wave for the IBM PC/XT and can find absolutely nothing on it.

Thanks for those links, through a lot of trial and error I figured out (For the most part) how the JrWave works. It's not quite like the JrCaptain when it comes to configuration of the RAM.

Some pics:
https://imgur.com/a/ezMBoEI

First, the JrWave seems to support 640k of RAM on board max, although all sockets are wired for 256k chips (meaning a total of 1meg) it only seems to use 256k chips in the right most banks. See my picture above. They were initially configured backwards in this board so when I ran the MEMTEST utility, all RAM looked OK but the segment test failed as I was getting reflections of RAM. It was basically trying to access the 64k chips as if they were 256k resulting in memory getting overwritten. Took me ages to figure out it was backwards. I also figured out the DIP switches (I am 99% sure) -- although 7 switches don't appear to be used. I an thinking they are maybe to control the 6 banks on the JrCadet which this board also supports. They seem to have no effect at all in any configuration. (There is a chart of switch settings in the Imgur link above.)

I have modified my board to take 5v power directly on the DC input jack by removing the bridge rectifier, 7805 and bulk cap. I then added two jumpers on the back and a 470uf cap on the board. My 5V comes right from the PicoATX support inside my PC.

Sadly, this all doesn't for me -- as soon as I configure the RAM, the computer becomes unstable. It sometimes allows me to run a program or two, but usually ends up freezing or giving a memory allocation error. Any RAM size I'm adding creates problems.... even though allowing the built in diagnostics or Tecmar's MEMTEST to run endlessly has zero issues.

Here's what I've tried:

• Every Possible RAM size configuration -- the system is slightly more stable using less memory, but only a little
• A full size ATX power supply (in case my PicoATX was causing an issue) -- no change at all
• CONPCJR (Tecmar) and JRCONFIG.SYS -- both yield exactly the same issues
• I'm using IBM PC DOS 2.11 (Patched) here but also tried IBM PC DOS 3.3 -- not difference either
• All chips on the JrWave have been reseated (With Deoxit) along with the DIP switches -- I was actually having some issues with those at first with odd behavior

So I'm at a loss at this point. It might be my PCjr that is the issue OR the memory board.... without another board to test, no real way to rule out either. This computer has been nothing but frustrating. (The floppy controller chip had an intermittent fault which is now fixed now I replaced it.)

Maybe someone else in the future who ends up with this board may find this information useful.

You should consider getting a jr-IDE. It adds an RTC and IDE interface as well as filling memory to the max of 768K. That would tell you if the problem is with the jr or the jrWave. I am not suggesting that you give up on the jrWave as I believe it is a great collector's item and should be repaired. Another suggestion might be the IBM 128k sidecars, if you have any. I have two but no idea what they are worth. With options like the jr-IDE, they aren't very useful, but they don't seem to be very common either.