HP41CX Copper Interconnectors

[JW]

How many copper interconnectors are there on the HP41CX - 2 or 3? (near the bottom of the calculator between the screw posts). On the HP41CV there are only 2 - their size is about an inch long by 1/8" wide by 1/16" thick held parallel by flexible clear plastc.

I was led to believe that on the HP41CX there were these 2 plus a third middle short copper interconnector about 3/8" long - is this correct?, and if so, why was a third copper interconnector added? - was it because of the added timer/clock module on the HP41CX?

Any photos of all the HP41CX copper interconnectors anywhere?

[Raymond Del Tondo]

The connection between the main pcb and the CPU board

is the same on the fullnut C, CV, and CX .

I have a C case with a CX CPU board inside,

and it works as it should.

The halfnut units have a redesigned hardware layout,

with the components near the top.

But I think that the board layout of halfnut

machines is the same for all configs (C, CV, CX).

Photos should be available here in the museum in the HP-41 section,

or in the repair/articles section.

[Randy]

All fullnut 41's are the same interconnect scheme regardless of model type (C,CV,CX). There are the two connection strips you describe opposite the two lower screw posts and the battery/port connector on the top posts. The only difference on the CX was the addition of the clock chip along with rom changes. This all fit on the same size circuit board. On later CV's, look for an empty 20 pin dip area - it's were the CX clock chip fit along the right side of the module.

The lower interconnects had three different forms over the life of the product (pink elastomerics, single thin gold wire strip, double thick wire strips).

The battery/port connector evolved as well with a foam pressure pad giving way to a harder rubber strip in later models.

Later halfnuts have only the battery/port connector. Everything else is on one single board for the C and CV, the CX clock module is an additional piggy back card that rests over the main cpu.

Edited: 26 Oct 2004, 7:05 p.m.

[Raymond Del Tondo]

I'm not quite sure,

but I think my first 41C had those metal needle pins

like in the card reader or the older HPs

to connect the CPU board to the kbd pcb.

At least some of my HP-41 CPU boards

still have the row of holes for the pins.

Raymond

[Randy]

I've seen the holes but never the pins. Where is David Smith when we need him?

Edited: 26 Oct 2004, 8:23 p.m.

[Tony Duell]

I've never seen one with pin contacts (and it's not mentioned in the service manual either). My early (1940Axxxx serial number, still with all the bugs mentioned in Wlodek's book) 41C has the pressure connector.

[JW]

I checked on the Museum web site as Raymond suggested and found this by Stefan Vorkoetter (under the Museum Home Page under Repairs and Batteries - Repairing the HP41CX):

http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/articles.cgi?read=2

and I quote from this artcle by Stefan:

"Notice the two rows of contact fingers between the top screw posts, and the two long rows and one short row between the bottom screw posts. (I think the 41C and 41CV don't have the short interconnect.)"

and

"On my HP-41CX, one of the three flexible CPU board to keyboard interconnects was missing. It was most likely lost during a previous repair attempt (the rubber feet were also missing). I decided to do away with the interconnects entirely, and hardwire the CPU board to the keyboard. This has the advantage that the connection will no longer rely on the integrity of the bottom screw posts."

and

"Next, cut 4 pieces of wire of the appropriate length to reach from the middle row of contacts on the keyboard to the corresponding contacts on the CPU board. Strip 1/8" insulation from each end, and solder them in place as shown."

This indicates on the HP41CX model that Stefan had, that there were 3 copper interconnectors between the screw posts - 2 long and 1 short(middle) - which he replaced with 16 + 16 + 4 soldered wire connections.

On the second of the pictures in this article by Stefan you can just make out the row of 4 extra contacts (LHS)in between the 2 rows of 16 contacts near the bottom screw posts.

[Diego Diaz]

Hi all,

Those pins are not intended for connecting the CPU board as they are "already" connected to it thru the "main" two rows.

Namely, (facing keyboard PCB with display on top) numbering left to rigth bottom and right to left top (just like the pins on an IC), we find that these four pads are connected to:

1 - 2 GND

2 - 32 Vcc

3 - 31 Vbat

4 - 23 Vin

It looks like just testing/power purposes so far.

Hope this helps.

Diego.