HP 3456A multimeter ROMS gone bad

I'm looking for ROM images for an HP 3456A multimeter. Mine has a bad ROM. snipped-for-privacy@hotmail.com

By the way, if you have this meter I advise that you back up your roms. The old Mostek ROMS have been known to go sour after 20 or so years. Same goes for the Genrad Digibridges etc.

If I can't get lucky here, then I have to blow $100 on another meter on eBay so I can dupe the roms.

Sorry about the crosspost, but you folks are most likely to own a 3456A and to have this info.

EPROM chips typically guarantee 10 years operation, and chip makers usually halve measured maxima to get a value for data sheets. E.g. if they run at 8 MHz, guarantee them to 4 MHz, if they lose charge in 20 years, guarantee to 10 years.

I'd say top up your EPROMs every

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Or even "Read, then re-write," without the erase. The uncharged bits will stay uncharged, and charged bits will be restored, yes?

If the failure is recent, one might still recover the original data from EPROMs and ROMs by reading them at lower-than-spec Vcc, thus reducing their sense-amps' thresholds. (The opposite technique -- increasing Vcc -- was used in programming many of these parts, to ensure the bits had adequate programming margin.)

Cheers, James Arthur

On 20 Apr 2005 03:56:27 -0700, Winfield Hill 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

Thanks for the usefull insight! Very good to know.

Stepan

The NEW revision of the ROM can be backfitted? What's it do?

--
 Thanks,
    - Win

By the way, the newer ROMS I listed below CAN be backfitted onto older instruments.

Stepan

I suspect it's just bug fixes. Would you like a copy of the service manual? over 300 pages and about 81 Megabytes. Painstakingly scanned in, and with full page 11x17 schematics at 600DPI.

Stepan

Would I, he asks, falling all over himself, picking himself up from the ground, mouth drooling and steam rising from his nose! Shall I send you a blank CDR in an sase? Or provide an ftp link?

--
 Thanks,
    - Win

In return, I'll offer a color scan of the elegant color version of the operator's manual, plus images of the ROM from my newest 3456A.

--
 Thanks,
    - Win

Crikey, just what kind of multimeter is it?!

Is that 81 Megs because you scanned it 600 dpi 24-bit colour and lossless image files?

K.

ftp link is fine, or send me an email address of yours, that I can use with

Yes the ROMS would be greatly appreciated but if that's too much to ask then I'll understand. It would be a pitty if I didn't share the manual.

email me at snipped-for-privacy@hotmail.com and not snipped-for-privacy@hotmail.com

Stepan

No, no. none of that nonsense. Just plain old 600DPI single bit bitmap, compressed to PNG. That preserves the halftones in full glory. The original manual is not in color.

Stepan

So it is grey scale 8-bit lossless compression, I see.

I do a fair bit of work turning scans of old documents into shiny new HTML.

800 pages is a _bit_ too much, but I tend to store the text in black and white, which is about 8 times smaller than greyscale and the OCR software handles. I snip out figures and circuits and store those in the form appropriate.

I found a company that makes scanners for books: it turns pages so you just set it going. Very expensive, but cheaper than hiring people to scan them and is generally only used for rare or outstanding books.

I wonder if there are companies that will scan books for you with such machines, and how much they'd charge if I sent them my bookshelves?

It's actually 1-bit grayscale. At 600DPI the halftones look great because the dot pitch of the halftones is less,so it is nicely sampled without too much aliasing. I'm guessing that compressing a 1-bit image into an 8-bit format works because it likely affects the dictionary and not the data aka pointers.

As far as scanning books, I suppose one could forgo the cost of an expensive scanner by just cutting the binding off a book and then useing a flatbed with a document feeder.

Stepan