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The
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Path: /hp/3456a/

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00readme:

Manuals for the hp 3456A Digital Voltmeter.
Compliments of Stepan Novotill.

rom_info:

HP no longer supports the 3456A and parts are no longer available.

The MK36XXX ROMS in this meter have been known to die of old age.
This used to be a common pinout. Equivalents are Signetics 2664,
AMI S68364, Harris HM6388, NS DM87S228, NS DM77S228. These ROMS
can be read on an EPROM programmer as a motorola MCM68766C35 aka
MC68766, which is a pin compatible EPROM used for prototyping.

To replace these ROMS with ordinary 2764 EPROMS you will need to
make a socket adapter with the following pin connection changes:
   EPROM-Vpp-pin-1 connects to +5V
   EPROM-PGM-pin-27 connects to +5V
   EPROM-/CE-pin-20 connects to GND
   EPROM-/OE-pin-22 connects to ROM-/CE-pin-20

         2764
    +----._.----+                  MK36xxx
 1 -|Vpp     Vcc|- 28               2364
 2 -|A12    /pgm|- 27          +----._.----+
 3 -|A7       nc|- 26       A7 | 1       24| Vcc
 4 -|A6       A8|- 25       A6 | 2       23| A8 
 5 -|A5       A9|- 24       A5 | 3       22| A9 
 6 -|A4      A11|- 23       A4 | 4       21| A12
 7 -|A3      /OE|- 22       A3 | 5       20| /CS
 8 -|A2      A10|- 21       A2 | 6       19| A10
 9 -|A1      /CE|- 20       A1 | 7       18| A11
10 -|A0       D7|- 19       A0 | 8       17| D7 
11 -|D0       D6|- 18       D0 | 9       16| D6 
12 -|D1       D5|- 17       D1 |10       15| D5 
13 -|D2       D4|- 16       D2 |11       14| D4 
14 -|Vss      D3|- 15      Vss |12       13| D3 
    +-----------+              +-----------+

        2564
     +----o----+
 Vpp | 1     28| Vcc   Pin 26 and 28 are connected
/CS1 | 2     27| /CS2
  A7 | 3     26| Vcc   internally only one is needed
  A6 | 4     25| A8
  A5 | 5     24| A9
  A4 | 6     23| A12
  A3 | 7     22| PD/PGM
  A2 | 8     21| A10
  A1 | 9     20| A11
  A0 |10     19| Q8
  Q1 |11     18| Q7
  Q2 |12     17| Q6
  Q3 |13     16| Q5
 Vss |14     15| Q4
     +---------+

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 part,
as long as the programer strobes CS or OE when reading
each consecutive address. Most will do that.

They can be directly replaced with pin-compatible EPROM
MC68766 or MCM68766C35 but these are obsolete though
easily available as surplus parts for about 10 dollars
each. The SCM90448C might also be a direct replacement.

Modern EPROM 27HC641 aka M27HC641 can be used and is pin
compatible, as long as you cook the data before burning,
because A10 and A12 (if I remember correctly) are swapped.

Three of EPROM 2764 can be used but a socket adapter
needs to be made to compensate for a few differences
in pinout. This is very very easy using wire-wrap sockets.

The data from the three ROMS can also be packed into a
single EPROM 27256 but a socket adapter must be made,
and a couple of address lines must be tied to the EPROM.

The data can also be split among 6 of EPROM 2732A if
you solder in the missing sockets and change around the
jumpering feeding the chip select decoding logic.

...Stepan

rom_info_rev:

These 314 png sheets were scanned in at 600dpi from the original HP
3456A manual, and special care was taken to preserve the halftones.

----------------------------------------------------------------
THE INFORMATION BELOW PERTAINS TO THE FIRMWARE ROMS IN THE 3456A
----------------------------------------------------------------

The three MK36XXX ROMS in this meter are 24 pin 8Kx8 mask ROMs.
They have been known to die or become corrupted due to old age.
This used to be a common pinout. Equivalents are Signetics 2664,
AMI S68364, Harris HM6388, NS DM87S228, NS DM77S228. These ROMS
can be read on an EPROM programmer as the pin compatible Motorola
MCM68766C35 aka MC68766 prototyping EPROM, as long as the reader
is smart enough to strobes CS or OE when reading each address.
Meters with serial numbers HIGHER-THAN 2015A03070 contain a NEWER
ROM revision having the following part numbers and checksums:
U5=1818-1629(C9CF5)   U7=1818-1630(CD212)   U8=1818-1631(D4CE2)
Notice that the newer ROMS are certified to work in older meters.

                      ---------------

The ROMS can be directly replaced with pin-compatible EPROM
MC68766 or MCM68766 but these are obsolete though easily
available as surplus parts for about 10 dollars each. The
SCM90448C might also be a direct replacement. Your EPROMS should
have the following checksums: U5=(C9CF5) U7=(CD212) U8=(D4CE2)
The procedure above is verified to work without any problems.
Modern EPROMs type 27HC641 aka M27HC641 should also work and are
pin compatible, as long as you cook the data a before burning,
because A10 and A12 pins (if I remember correctly) are swapped.

                      ---------------

The data from each mask ROM can be split into two ordinary 2532
type EPROMs which are easily available. You just need to solder
in the 3 missing ROM sockets and change the jumpers at the chip
select logic on PCB A4 as follows. Remove jumpers: 2-3, 4-5, 7-8
and install the following new jumpers instead: 1-2, 5-6,8-9, 4-7.
Split the original ROM from socket U5 across sockets U1 and U2.
Split the original ROM from socket U7 across sockets U4 and U5.
Split the original ROM from socket U8 across sockets U7 and U8.
The checksums for the six split ROMS will turn out as follows:
U1=(65C3C) U2=(640B9) U4=(6581A) U5=(679F8) U7=(6DBED) U8=(670F5)
The procedure above is verified to work without any problems.

                      ---------------

To replace these ROMS with ordinary 2764 EPROMs you will need to
make a socket adapter with the following pin connection changes.
This is very easy if you use a wire-wrap socket having long pins.
   EPROM-Vpp-pin1 connects to +5V
   EPROM-PGM-pin27 connects to +5V
   EPROM-VCC-pin28 connects to +5V
   EPROM-/CE-pin20 connects to GND
   EPROM-/OE-pin22 connects to ROM-/CE-pin20
   EPROM-A11-pin23 connects to ROM-A11-pin18
   EPROM-A12-pin2 connects to ROM-A12-pin21
To replace these ROMS with ordinary 2564 EPROMs you will need to
make a socket adapter with the following pin connection changes.
This is very easy if you use a wire-wrap socket having long pins.
   EPROM-Vpp-pin1 connects to +5V
   EPROM-/CS1-pin2 connects to GND
   EPROM-/CS2-pin27 connects to GND
   EPROM-VCC-pin28 connects to +5V

      2764                                       2564
   +----o----+             MK36xxx            +----o----+
1 |Vpp   Vcc| 28          2364           Vpp | 1     28| Vcc
2 |A12  /pgm| 27       +----o----+      /CS1 | 2     27| /CS2
3 |A7     nc| 26    A7 | 1     24| Vcc    A7 | 3     26| Vcc
4 |A6     A8| 25    A6 | 2     23| A8     A6 | 4     25| A8
5 |A5     A9| 24    A5 | 3     22| A9     A5 | 5     24| A9
6 |A4    A11| 23    A4 | 4     21| A12    A4 | 6     23| A12
7 |A3    /OE| 22    A3 | 5     20| /CS    A3 | 7     22| PD/PGM
8 |A2    A10| 21    A2 | 6     19| A10    A2 | 8     21| A10
9 |A1    /CE| 20    A1 | 7     18| A11    A1 | 9     20| A11
10 |A0     D7| 19    A0 | 8     17| D7     A0 |10     19| D8
11 |D0     D6| 18    D0 | 9     16| D6     D1 |11     18| D7
12 |D1     D5| 17    D1 |10     15| D5     D2 |12     17| D6
13 |D2     D4| 16    D2 |11     14| D4     D3 |13     16| D5
14 |Vss    D3| 15   Vss |12     13| D3    Vss |14     15| D4
   +---------+          +---------+           +---------+

Your EPROMS should have the following checksums: U5=(C9CF5)
U7=(CD212) U8=(D4CE2). The procedure above is verified to work
without any problems but is a bit messy and time consuming.

                      ---------------

The data from the three original ROMS can probably also be packed
into a single 27256 EPROM but a socket adapter must be made, and
a couple of address lines from the chip select logic must be tied
to the EPROM.

                      ---------------

If replacing the ROMS does not work then try a new CPU:
   MC68A00P or HD468A00P which runs at 1.5MHz

                      ---------------

The 8048 MCU on PCB A30 in the meter is a mask ROM part which
can be read on many EPROM programmers as an Intel 8748 MPU.
You can then burn the image into an Intel C8748 EPROM MCU part.
The checksum for a good 8048 binary ROM image is 1C936.
The procedure above is verified to work without any problems.

...Stepan

Files:

3456A Operators Manual Part 1 of 2.PDF
(8.7 MB)
3456A Operators Manual Part 2 of 2.PDF
(7.5 MB)
3456A-mil_calibration_manual.pdf
(64 KB)
3456a_op_and_service_high_res.pdf
(42 MB)
Catalog pages for Hp3456A.pdf
(240 KB)