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HP-41C LCD display and driver
01-20-2020, 08:47 AM
Post: #1
HP-41C LCD display and driver
Hi All,
I've just got back into the world of HP calculators after a ~40 year absence! I've bought not one but three HP-41 calculators from TAS. The first CV needed a repair with Diego's excellent I/O module foil, and I cannibalized the other machines so that this one has original module covers and side covers. The #2 machine was an HP-41C, but now has the display and 41CV module from the third machine. With me so far?

The third machine is in a bit of a sorry state. It was a Zengrange Gunzen, so has the rubberized front panel and no access to the User, Prgm and Alpha keys - hence this one being cannibalized for parts for #2. However, it does work after a fashion. I've cleaned and dried the front panel / keyboard and this seems to be working OK. The big problem is that the upper segments of the display are ghostly. Slight pressure on the LCD restores the upper segment display, so I think some crud or corrosion has got into the display assembly.

Having transplanted displays, I'm confident in removing the display assembly again for examination, but I think I need to separate the LCD from the driver board to find out what's going on there. I've looked at page 3-4 of the service manual, but the pictures are not very distinct. I've also looked at photos at https://s839.photobucket.com/user/hewpac...ort=6&o=14, which show that it can be done.

Does anyone here have experience in separating the LCD from the driver board to examine and clean it? I don't want to break the display assembly, but it's only half working at the moment.

HP-41C, HP-41CV, HP 50g, HP 35s, HP Jornada 420, DM41X β
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01-20-2020, 03:37 PM
Post: #2
RE: HP-41C LCD display and driver
The metal clips shown in the photo hold the sandwich of the board and the glass, with a permissive and compressible connection material between them, together. The display shown appears to have the wire coils type of interconnect, however any that I have taken apart has the elastomer type interconnects. I have taken them apart and cleaned the connection points, and successfully put them back together. It is important to use lint free cloths to clean as any tiny bit of lint you leave behind may result in a failed connection.

Paul.
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01-21-2020, 03:38 PM
Post: #3
RE: HP-41C LCD display and driver
(01-20-2020 03:37 PM)Paul Berger (Canada) Wrote:  The metal clips shown in the photo hold the sandwich of the board and the glass, with a permissive and compressible connection material between them, together. The display shown appears to have the wire coils type of interconnect, however any that I have taken apart has the elastomer type interconnects. I have taken them apart and cleaned the connection points, and successfully put them back together. It is important to use lint free cloths to clean as any tiny bit of lint you leave behind may result in a failed connection.

Paul.

Thanks Paul. Mine are the elastomeric type. I've cleaned them but no improvement, so I assume that the display itself is damaged.

HP-41C, HP-41CV, HP 50g, HP 35s, HP Jornada 420, DM41X β
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