Thank you, Geoff Quickfall

[Geir Isene]

This worked wonders:

Help with HP-41 keyboard issue.

[Matt Agajanian]

Wait a minute! I'm a little confused here. According to the Archive thread you referenced, an HP-41CV was transformed into a CL. When I sent a message to Randy at FixThatCalc a month ago, he told me that because of the motherboard, only a CX can be upgraded to a CL. So, could someone clarify which 41s are suitable for CL upgrade?

[M. Joury]

Nope. 41CV's work fine as donor bodies. You can probably find all the info you want here.

Cheers,

-Marwan

[Ángel Martin]

Quote:

---

could someone clarify which 41s are suitable for CL upgrade?

---

Fullnuts.

[M. Joury]

There are a couple of other possible limitations. Beyond "Having a square cornered display" here is the relevant section from the V3 manual:

Hewlett-Packard changed the display driver circuitry in the 41 series during production,
and this change affected one component value on the CPU circuit board. The 41CL circuit
board implements the component value used in later production units. Units with the correct
display driver can be identified as follows:
• If your 41C (not CV or CX) has a serial number starting with “1954” or larger it uses
the correct display driver.
• If your 41CV/CX has a serial number starting with “2003” or larger it uses the correct
display driver.
It is theoretically possible to use the 41CL circuit board with the older display driver, but
this requires soldering an extra capacitor to either the 41CL circuit board or to the calculator
main board. If you really want to upgrade a calculator that uses the older display
driver, please contact us directly for details.
In addition to the display driver change, Hewlett-Packard also experimented with a different
method of connecting the CPU board to the main board. Unfortunately it is not possible
to identify units that used this different connection method via the serial number.

I hope it is ok to post this here.

Cheers,

-Marwan

[Matt Agajanian]

Okay, here's what I have:

I've got a 41CV with a rounded display corners and serial number starting with 26 and another 41CV with a straight corner display with a serial number starting 24. Which 41CV qualified for a CL upgrade?

Edited: 3 May 2012, 4:43 p.m.

[M. Joury]

Not the one with rounded display. The other should work just fine. BUT, please note the following (also pasted in my earlier email):

Quote:

---

In addition to the display driver change, Hewlett-Packard also experimented with a different
method of connecting the CPU board to the main board. Unfortunately it is not possible
to identify units that used this different connection method via the serial number.

Identifying such a calculator is a step in the installation process covered in the next section.

---

Edited: 3 May 2012, 5:12 p.m.

[Geoff Quickfall]

Matt check this link:

HP 41 donors suitable for CL CONVERSION.

Cheers, Geoff

Both my CL's are 1979 tall key HP 41Cs

Edited: 6 May 2012, 8:02 p.m.

[Matt Agajanian]

Hi Geoff. Thank you for the clarification. As I have one of each (a rounded- and square-corner display 41CV), I'm certain, at least the straight-edged one can get the CL treatment.

Thanks for explaining why.

Matt

Edited: 6 May 2012, 11:33 p.m.