Would anyone know of a source for a CPU for the HP 35. My 35 has some sentimental value and I would like to get it repaired. Also is there a source for the battey/ foil strip for the 41C/Cv/CX?


Since these chips haven't been made in almost 30 years, the only source is another 35, 45, 46, 55, 65, 70, 80, 81, 9805, or 1722 oscilliscope.

The CPU consists of two chips, the CTC and the ARC. Which one are you trying to replace, and how do you know that it has failed? There is also a clock driver, three ROMs, an anode driver, and a cathode driver.


I'd love to see you extract the individual A&R and C&T chips from an HP65!.

For those who don't realise the problem, the other classic-series machines have the A&R chip in a 16 pin DIL package, the C&T chip in a 28 pin one. They are easy to desolder from the PCB. The HP65 contains a multi-chip module (44 pins IIRC), containing 6 silicon dice, believed to be the A&R, C&T, clock buffer, card reader controller and 2 RAMs. The ROMs are certainly external, apparently so the firmware could be updated without replacing the multi-chip module.

I believe my notes on these machines (giving pinouts and testpoints) are in the articles forum here. There are schematics on the HPCC CD-ROM, but there's no data on the _internals_ of the multi-chip module.


If you send me a hybrid, I'd be happy to extract the A&R and C&T chips from it for you. I'll do that for free (just pay the postage both ways), but if you want them bonded out in ceramic DIP packages, that will cost a few hundred dollars.


Eric, I've got an intermittant one if you want it. I haven't decapped it but I suspect it is nothing more than a failed wire bond. I also have some Pioneer's (10B/20S) and a 10Bii for the project if you're still looking.


Hi Tom. Eric is right, the CPU is a somewhat primitve two chip

I would suggest that you consider sending me your calc for repair.
Unless the calc has been subjected to "abuse", disassembly and
fiddling with the electronics, the actual devices are fine and it's an interconnect or cracked board problem.

I am pretty seasoned at digital (and analogue) electronics repairs.
I built my first "computer" from chips according to my own design
in 1984, so I know what I am doing ;-)

I worked for Canon Auistralia in my first full-time job in 1985,
repairing calculators (all kinds!) and desk-top computers.

If you want me to repair your machine, please write to me at:


stating in as much detail as possible what is wrong (won't turn on, strange display, crashes when running a program, bad keys, etc...)
and how it got that way (got wet, dropped, on charger without
battery pack inserted or battery leaked, etc...)

Only trying to help.

Best wishes,

Don Wallace


There are no sources for the interconnects for the 41C series.
The products are long dead.

Some people like myself can repair the flexible pcb's.
I have an aging 41C fullnut silverbird (one of the first non buggy
ones out of the U.S.A.) and have done extensive repairs on it a number times, including repairs to the flexible interconnect you are talking about. My 41CV is 100% functional, although 24 years old.

If interested, write to me.

Don W


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