Google Groups no longer supports new Usenet posts or subscriptions. Historical content remains viewable.
Dismiss
PC Convertible (Type 5140) LCD display notes
118 views
Skip to first unread message
RickE
Sep 30, 2023, 11:24:48 AM9/30/23
to
Greg kindly sent me his 5140, which has a working battery pack (very low capacity, but working) and the 3rd generation backlit display. Unfortunately, the LCD isn't displaying any characters -- the backlight works and the level is adjustable, the contrast control also works, but it just changes how well you can see the few vertical bars that appear. The display is recognized by the system, so I'm not getting the one long and two short beeps that you would get from the 5140 when no LCD is installed.
When I took the display out of the front/back covers, I found that the foam material between the back and the circuit board had degraded significantly -- not quite to the the "black goo" level, but very sticky. The good news is that the degraded foam had not become conductive, so 5140 owners don't have to worry that bad foam will cause their displays to fail. The bad news for me is that the display problems are internal. The board is made by Epson and is labelled TCM-A0270. It has sixteen Toshiba T7778 modules and three Toshiba T7900s. The board is mostly (not completely) free of corrosion, so I still have a chance that the problem is a short or bad connection on the outside of the board -- it needs a long and careful cleaning. If I do have to "dive in", there are 25 metal tabs that need to be straightened to remove the board, and I don't see any alignment pins or slots to help me put it back together. But I think the entire metal frame just sits around the display assembly, so perhaps the alignment is not critical.
Rick
When I took the display out of the front/back covers, I found that the foam material between the back and the circuit board had degraded significantly -- not quite to the the "black goo" level, but very sticky. The good news is that the degraded foam had not become conductive, so 5140 owners don't have to worry that bad foam will cause their displays to fail. The bad news for me is that the display problems are internal. The board is made by Epson and is labelled TCM-A0270. It has sixteen Toshiba T7778 modules and three Toshiba T7900s. The board is mostly (not completely) free of corrosion, so I still have a chance that the problem is a short or bad connection on the outside of the board -- it needs a long and careful cleaning. If I do have to "dive in", there are 25 metal tabs that need to be straightened to remove the board, and I don't see any alignment pins or slots to help me put it back together. But I think the entire metal frame just sits around the display assembly, so perhaps the alignment is not critical.
Rick
IBMMuseum
Oct 2, 2023, 2:36:01 AM10/2/23
to
I picked up absolutely NIB 5140 LCDs at Computer Reset two years ago, and almost all look bad (Texas heat in the warehouse area) - If I find one that works, I can send it your way. Otherwise, I was using a CRT 'slice', Berg-to-DE9 dongle, then RGB2HDMI converter to get a modern display (and video output I can capture, rather than using my camcorder on that horrible screen). The LCD pinout is in the Tech Ref at the 'Ardent-Tool'.
RickE
Oct 3, 2023, 1:29:02 PM10/3/23
to
On Monday, October 2, 2023 at 2:36:01 AM UTC-4, IBMMuseum wrote:
> I picked up absolutely NIB 5140 LCDs at Computer Reset two years ago, and almost all look bad (Texas heat in the warehouse area) - If I find one that works, I can send it your way. Otherwise, I was using a CRT 'slice', Berg-to-DE9 dongle, then RGB2HDMI converter to get a modern display (and video output I can capture, rather than using my camcorder on that horrible screen). The LCD pinout is in the Tech Ref at the 'Ardent-Tool'.
I did bend the metal tabs and took the frame off the display assembly, then I found what I expected -- two long strips of "rubber" with conductive sections that run along the top and bottom sides of the LCD which connect the PCB pads with the LCD pads. This was "the way it was done" in the early LCDs, but the industry moved away from this connection design because the long-term reliability was poor. My odds of getting those to line up properly again are slim and none, and it could well be that the true fault is in one or more of the large Toshiba modules. Greg included the CRT slice (and printer and serial/parallel) in the box, and I have a PCjr CRT display adapter dongle around here somewhere, plus I have a spare first generation 5140 LCD with one "dead line", so I've got options for the Convertible display. Mostly I'm trying to figure out if I want to move parts from Greg's 5140 into my second 5140 to make it "almost perfect", or do it the other way around. My first 5140 has pretty much everything except for the speech adapter, it's very nice.
> I picked up absolutely NIB 5140 LCDs at Computer Reset two years ago, and almost all look bad (Texas heat in the warehouse area) - If I find one that works, I can send it your way. Otherwise, I was using a CRT 'slice', Berg-to-DE9 dongle, then RGB2HDMI converter to get a modern display (and video output I can capture, rather than using my camcorder on that horrible screen). The LCD pinout is in the Tech Ref at the 'Ardent-Tool'.
IBMMuseum
Oct 3, 2023, 1:54:33 PM10/3/23
to
> ...My first 5140 has pretty much everything except for the speech adapter, it's very nice.
Some Speech Adapters for the PCjr (on a Facebook group specifically for it) have come up recently - but not for the 5140.
Some Speech Adapters for the PCjr (on a Facebook group specifically for it) have come up recently - but not for the 5140.
gfre...@aol.com
Oct 5, 2023, 8:38:42 AM10/5/23
to
On Sat, 30 Sep 2023 08:24:47 -0700 (PDT), RickE <ekb...@vnet.ibm.com>
wrote:
I didn't get to play with it because the power wasn't working right
but can't you just plug the composite out from the monitor slice into
a TV? That should give you as good a picture as you are getting from
composite video.
wrote:
but can't you just plug the composite out from the monitor slice into
a TV? That should give you as good a picture as you are getting from
composite video.
RickE
Oct 8, 2023, 9:40:02 PM10/8/23
to
On Thursday, October 5, 2023 at 8:38:42 AM UTC-4, gfre...@aol.com wrote:
> I didn't get to play with it because the power wasn't working right
> but can't you just plug the composite out from the monitor slice into
> a TV? That should give you as good a picture as you are getting from
> composite video.
Yes, that should be completely doable. I haven't tried it yet because I've been working hard on my outdoor projects while we have nice weather, but I used to run my 5140 with both the LCD screen and the display slice (and sometimes with the display slice alone), and used both the 5144 and 5145 monitors I had to connect "both ways". The display looked crisper on the 5145 than the 5144, so if I was going the "slice only" route I'd want to find or re-create the PCjr display cable and use a RGB2HDMI device to attach it to a modern TV. I no longer have the 5144 or 5145, I scrapped both of them a few years back when I was doing some major "clean out the attic" activity (along with at least 800 pounds of various and sundry computer and electronics equipment).
> I didn't get to play with it because the power wasn't working right
> but can't you just plug the composite out from the monitor slice into
> a TV? That should give you as good a picture as you are getting from
> composite video.
0 new messages