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Inductor on HP 25C board
09-22-2015, 07:31 AM
Post: #6
RE: Inductor on HP 25C board
(09-21-2015 08:50 PM)Harald Wrote:  All the registers are working and retain their contents even when the calculator is turned off.
LastX in deed always returns zero. So I guess it is that RAM chip that is bad. Which one is it? Unfortunately the IC markings aren't legible any more.

I don't have knowledge about which RAM represents registers and program. You have to remove one of it to find out.

Each of the two CMOS RAMs in HP-25C contains 8 registers, which is 56 byte. The PMOS RAM in HP-25 contains 16 registers in a single chip. I had a defective HP-25 RAM which consequently lost both memories, program and registers.

Bernhard

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Messages In This Thread
Inductor on HP 25C board - Harald - 09-21-2015, 09:36 AM
RE: Inductor on HP 25C board - Harald - 09-21-2015, 03:48 PM
RE: Inductor on HP 25C board - PANAMATIK - 09-21-2015, 07:18 PM
RE: Inductor on HP 25C board - Brad Barton - 09-30-2015, 04:49 PM
RE: Inductor on HP 25C board - Harald - 09-21-2015, 08:50 PM
RE: Inductor on HP 25C board - PANAMATIK - 09-22-2015 07:31 AM
RE: Inductor on HP 25C board - jebem - 09-22-2015, 08:49 AM
RE: Inductor on HP 25C board - Harald - 09-22-2015, 01:47 PM



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