Mike's PCjr Page

I know most of my recent posts have been related to these, but

I just parted with twenty-six bucks to purchase a new card out of desperation to get my system running again.
I currently have two non functional cards that I'm not getting power from.

It seems to be a problem other than the usual fuse that tends to blow and I'm not sure what is wrong with them, but I'm assuming it's a few I don't know about. I'll have to look into it more than I have. Maybe in the technical reference manual.

They are the short cards. WHEN I do get them working (Someyear) I think it would be best to trade them for other accessories rather than sell them or keep them around.

I hate reading posts like that. Good on you for saving the cards to fix them later. But the cost of the replacement card was too much.

Contact me first next time. I need to pare down some of my systems and spare parts. (People who have been here a while get first consideration and the "friends and family" pricing.)


Mike

Man, I really need to get on with that replacement power PCB design that I was talking about doing a while back. I've been working on other projects and just haven't had the cash free to order the parts I want to experiment with.

Brutman wrote:I hate reading posts like that. Good on you for saving the cards to fix them later. But the cost of the replacement card was too much.

Contact me first next time. I need to pare down some of my systems and spare parts. (People who have been here a while get first consideration and the "friends and family" pricing.)


Mike

Yeah, I'm usually not a "part swapper", but I was a bit desperate to get this thing running again. Hopefully I get the cards working again and get them back out there soon.
Also, I'll remember to contact you next time. There's a chance I'll need a sidecar shell in the future... that and an IR Module.

jmetal88 wrote:Man, I really need to get on with that replacement power PCB design that I was talking about doing a while back. I've been working on other projects and just haven't had the cash free to order the parts I want to experiment with.

The thought of a low weight, high wattage PSU in a PCjr is quite an exciting thought and such a thing would go great with a JRIDE and a bunch of expansions, wouldn't it?

I wish I could say I have enough time to contribute to it, but I gotta admit that currently lack enough knowledge to really do anything properly, but I'm sure I can learn more than a bit from it if I follow along and all that.

I am capable of populating PCB with SMD and do have a basic understanding of electronics, but not enough to design a board that will safely power the PCjr.


I'm really just an end-user that modifies and repairs existing devices.

I just got the new card and it doesn't seem to be working. >_<

The person I purchased it from said that it was tested, so this make me wonder if it's actually the brick being a piece of crap this time.


The multireader reads between 3v-6.7v.
This is supposed to be 16.7, isn't it?


Help?

Yeah, I think the brick is supposed to be putting out 17 or 18 volts AC.

I'm getting 3. I guess I'll crack this open and see what's what. Didn't Mike say that this things are glued together?

I was finally able to break into that brick, (Which wasn't the prettiest way to do it, I'm sure there's more effective ways, but...) and it turns out that the five amp fuse actually was blown.
http://img33.imageshack.us/img33/5499/uddp.jpg
http://img15.imageshack.us/img15/346/3y0b.jpg
At least this thing is just a simple transformer setup, I was expecting some PCB to be in there. If that was the case, I would have depopulated the board and produced some high res scans. ...Too bad it wasn't. ;P

I thought of an interesting case replacement idea for this, but first I'll replace that fuse.


Oh! And happy Independence Day!


EDIT: Remind me to start using thumbnails as hyperlinks to the full resolution images or something...

I can't thank you enough, Mike.
I got the Power brick and stuff from you and everything is working great!


I checked all of the solder joints from my modifications and made sure everything was in place before testing it all out.
Everything seemed to work fine for a second, but then the LM358 on the mobo burned to a crisp.

I removed the power card and after inspecting it, it seemed to be a newer revision of the cards I've seen.
It's the small card with a few oddities: First off, the coil is slightly different, The second thing I noticed is one cap is a completely different rating than usual, another thing is that another capacitor has the cathode pointing down rather than to the left (Which shows the PCB is also different) and aside from a few different different components, the weirdest thing I noticed is that the stuff that was done to UA723CN.

The first three pins have been jumped and pin ten of this has has been jumped to a nearby 200 Ohm resistor with another 200 Ohm resistor.


This is all seems to be clean enough to have been done at assembly, but I haven't heard of such a revision... not that I would know much about it.
I'll take some readings and see if the voltages are different or something. I'll also snap some pics and upload those, too.
This will all have to be later.
--
Anyway, I replaced that burned up OP Amp and went back to using the other board I have and after some tests, she seems to be running well... and no smoke either!



There's one new problem, though. The sound is really whiny. I'm not sure what cause this new problem, but when I try to play sounds, they are very faint. No matter what display I'm using.
If I'm using the colr Display, it's very faint and if I'm using a TV, I can't hear anything. There's some yellow wire wrap that jumps a pin on the display cable to the RCA jack for audio and it's still in place.

I'll try to figure out what is causing that, but any help is welcome and appreciated.

Edit: I fixed this problem.



One thing is for sure though and that is that my PCjr is ready for Jr-IDE and I'm really excited to assemble one and get it installed!

I have heard that the fuse in the brick is a common point of failure but I have never had one fail. I also know that breaking into a brick is not fun, as shown by your photo. Which kind of explains this abomination:

http://www.brutman.com/pics/2009_0329_161949.jpg

Yes - that is the innards of two bricks using a single cord to the wall. I presume it was used on a Racore/Rapport setup or something similar that needs two power supplies. It is really ugly and I've been scared to plug it in. Somebody had to work hard to get into two bricks, so I presume it happened when a fuse needed to be changed.

I know there are two major revisions of the power card - the short card putting out 33 watts and the long card putting out 45 watts. I don't know how many engineering changes there were that were not major like what you discovered.

I don't think the motherboard or anything else except they keyboard had more than one revision. The keyboard revision was not significant either - just mechanical. The innards are pretty much the same. But the power sidecar was definitely a cause of concern for IBM.