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faulty 41cv memory chip - Printable Version

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faulty 41cv memory chip - g. fernandez - 01-24-2005

Anyone does have a memory chip from a not functioning HP41CV labelled 1LE7-0005 or similar? is for repairing an HP41CV. When I do XEQ SIZE 000, it shows 255 steps only instead 319. Can I put a single memory module (HP82106A) on my HP41CV instead soldering a good memory chip?


Re: faulty 41cv memory chip - Tony Duell - 01-24-2005

IIRC the (user) RAM chips in the 41CV are 64 registers each. You could remove the faulty one and fit a single memory module in the appropriate port (Port 4, here, I think).

Alternatively (and I did this once), you can crack open the memory module and desolder the PCB from the connector. Then wire the PCB's pads to the holes for the original RAM chip, inside the 41. You need to connect the B3 and B4 pads correctly to put the module at the right address (Look at the I/O assembly schematic in the service manual to see what I mean). That way you still have 4 external ports for ROMs or peripherals.

Re: faulty 41cv memory chip - g. fernandez - 01-24-2005

B3 and B4 are two metallic connectors of the HP82106A memory module, right? The module has twelve connectors, 6 upper and 6 lower. What pins are B3 and B4? (They must be tied to VCC)
Also, what is the difference between a 1LE7-0005 and an 1LE7-0004 chip? Both are memory chips, have the same number of pins, but it seems to me that cannot be exchanged.

Re: faulty 41cv memory chip - Tony Duell - 01-24-2005

If you take the memory module apart, you can desolder the connector from the PCB, leaving 12 pads in a line. 2 of those (or equivalently 2 of the pins on the connector) are B3 and B4.

I assume you have an HP41 service manual. The pinout of the port is shown there. B3 and B4 are labelled. If you can't find it, I'll look it up for you.

The memory chips inside the 41 are designed to respond to particular addresses. That's the difference, I think, between the -0004 and -0005 chips. Corresponding pins on the different RAM chips are linked together on the PCB, there is no external chip select logic.

Re: faulty 41cv memory chip - g. fernandez - 01-24-2005

Thank you very much for your responses! Don´t worry, I have the HP41 service manual (PDF file).

Re: faulty 41cv memory chip - Tony Duell - 01-24-2005

If you need any more help, please feel free to ask....

Re: faulty 41cv memory chip - Diego Diaz - 01-25-2005


I'll gladly send you a clean memory module (without housing) to do the job.

Just mail me with your address, and I'll drop a pair of'em into an envelope to you.

Best regards.


Re: faulty 41cv memory chip - Gonzalo Fernandez - 01-25-2005


Mi dirección es: gonzalo_fernandez@apb.es, he intentado enviarte un email pero me da error.

saludos: gonzalo

Re: faulty 41cv memory chip - V-PN - 01-26-2005

PDF service to me, please?