Re: HP 3456A multimeter ROMS gone bad

On 20 Apr 2005 03:56:27 -0700, Winfield Hill
<hill_a@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> asked:

What kind of PROM did they use? What kind
of modern EPROM / EEPROM would be used in replacement?

Answer:

Meters with serial numbers HIGHER-THAN 2015A03070
contain a NEW revision of the ROMS with part number:
U5=1818-1629 U7=1818-1630 U8=1818-1631

The meter contains three 8Kx8 ROMS. These ROMS can
be read on an EPROM programmer as an MC68766, as
long as the programer strobes CS or OE when reading
each consecutive address.

They can be directly replaced with pin-compatible EPROM
MC68766 or MCM68766C35 but these too are obsolete.

EPROM 27HC641 can be used and is pin compatible, as
long as you cook the data before burning, because A10
and A12 (if I remember correctly) is swapped.

EPROM 2732 can be used if you split the data and solder
in the extra sockets and make some jumper changes etc.

EPROM 2764 can be used but a socket adapter needs to
be made.

EPROM 27256 can be used but the data needs to be cooked
and an intersocket socket adapter made.

....Stepan
.

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