Instrument Displays MDPM-3 nixie DPM (was Re: Service Manual/Schematics for an IBM 7861-015 modem?)
14 Feb
2007
14 Feb
'07
1:02 p.m.
On 2/12/07, Ethan Dicks <ethan.dicks at gmail.com> wrote:
On 2/11/07, Brent Hilpert <hilpert at cs.ubc.ca>
wrote:
OK... I've taken it apart to have a look... the IC dates are late 1968
- there are a few DIPs and a number of 8-pin epoxy-covered
button-shaped ICs all over the innards. The DPM came with a 36-pin
AMP connector with 4 wires loaded, two for power and two for input
voltage. The power wires go right into a transformer at the back of
the unit, leading me to suspect that it takes 110VAC, but perhaps it
takes 24VAC. I have not yet powered it up - does anyone have any idea
what it would take to fire it up?
The nixie tubes, for those who track such things, are 3 Burroughs
B-5750 7/8"(?) nixies, with a block next to them for "1", "+",
and "-"
(3 individual neons). The legend on the front proclaims it to be a
"mini-diget dpm".
I've never fiddled with a pre-LED DPM, so if anyone knows what voltage
it's expecting, I can fire it up to see if it works or is merely a
source of nixies.
Thanks,
-ethan
Ethan Dicks wrote:
Had a good day at the Mansfield Hamfest today. I
now have [a]...
nixie-tube panel DVM...
^^^^^^^^^^^^^^^^^^^^ If that is a Weston 1294-series DVM (4.5 digits,
TTL, fits standard 4"*1.75"
industrial instr. panel), I can supply the schematic.
It _is_ 4.5 digits... and does fit a standard panel opening, but
it's an MDPM-3 by Instrument Displays, Inc., of Haverhill, Massachusetts. 
14 Feb
14 Feb
4:20 p.m.
New subject: Instrument Displays MDPM-3 nixie DPM (was Re: ServiceManual/Schematics for an IBM 7861-015 modem?)
Ethan Dicks wrote:
The epoxy-button (with ceramic base) ICs sound like Fairchild's TO-5
alternative to the metal can TO-5/TO-99 package. They produced (at least) some
SSI RTL and Counting MicroLogic ICs in that package.
Considering the date and application, (many of) the ICs are likely Fairchild
Counter MicroLogic. This was a small family specifically directed at decade
counter/display strings. The technology can be described as MSI RTL, although
the 960 was sometimes used with TTL.
9958 or 958: decade counter TO-5 or 14-pin DIP
9959 or 959: 4-bit latch 16-pin DIP
9960 or 960: nixie decoder/driver 16-pin DIP
9989 or 989: mod-16 counter TO-5 or 14-pin DIP
Supply voltage is 3.3V to 5.5V.
Are there only date codes and no part numbers on the ICs?
It _is_ 4.5
digits... and does fit a standard panel opening, but
it's an MDPM-3 by Instrument Displays, Inc., of Haverhill, Massachusetts.
OK... I've taken it apart to have a look... the IC dates are late 1968
- there are a few DIPs and a number of 8-pin epoxy-covered
button-shaped ICs all over the innards. The DPM came with a 36-pin AMP connector with 4 wires loaded, two for power and
two for input
voltage. The power wires go right into a transformer at the back of
the unit, leading me to suspect that it takes 110VAC, but perhaps it
takes 24VAC. I have not yet powered it up - does anyone have any idea
what it would take to fire it up?
..could fire it up at 24VAC and see if the logic supply level makes
any sense, then go for 110 if not, although my guess would be 110.
FWIW, the Weston Nixie DPM I have is 110VAC.
The nixie tubes, for those who track such things, are
3 Burroughs
B-5750 7/8"(?) nixies, with a block next to them for "1", "+",
and "-"
(3 individual neons). The legend on the front proclaims it to be a
"mini-diget dpm".
I've never fiddled with a pre-LED DPM, so if anyone knows what voltage
it's expecting, I can fire it up to see if it works or is merely a
source of nixies.
4:51 p.m.
New subject: Instrument Displays MDPM-3 nixie DPM (was Re: ServiceManual/Schematics for an IBM 7861-015 modem?)
On 2/14/07, Brent Hilpert <hilpert at cs.ubc.ca> wrote:
Ethan Dicks wrote:
The epoxy-button (with ceramic base) ICs sound like Fairchild's TO-5
alternative to the metal can TO-5/TO-99 package. They produced (at least) some
SSI RTL and Counting MicroLogic ICs in that package.
Sure... counters make sense for a DVM/DPM made of discrete ICs (I've
been reading Don Lancaster's "TTL Cookbook" recently).
It _is_
4.5 digits... and does fit a standard panel opening, but
it's an MDPM-3 by Instrument Displays, Inc., of Haverhill, Massachusetts.
OK... I've taken it apart to have a look... the IC dates are late 1968
- there are a few DIPs and a number of 8-pin epoxy-covered
button-shaped ICs all over the innards. The DPM came with a 36-pin Considering the date and application, (many of) the
ICs are likely Fairchild
Counter MicroLogic. This was a small family specifically directed at decade
counter/display strings. The technology can be described as MSI RTL, although
the 960 was sometimes used with TTL.
Sounds reasonable.
9958 or 958: decade counter TO-5 or 14-pin
DIP
9959 or 959: 4-bit latch 16-pin DIP
9960 or 960: nixie decoder/driver 16-pin DIP
9989 or 989: mod-16 counter TO-5 or 14-pin DIP
Thanks for the numbers.
Are there only date codes and no part numbers on the
ICs?
There are part numbers on the ICs, but I can only read the DIPs; the
TO-5s are too hard to read as the numbers wrap around the packages and
I don't think I can really dismantle this further without desoldering.
> AMP connector with 4 wires loaded, two for power
and two for input
> voltage....
..could fire it up at 24VAC and see if the logic
supply level makes
any sense, then go for 110 if not, although my guess would be 110.
Hmm... as long as damage at 24VAC isn't likely.
FWIW, the Weston Nixie DPM I have is 110VAC.
Unsurprising, since nixies want 170V to 300V (according to the B-5750
datasheets). I just didn't want to fry mine out of ignorance.
-ethan
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ethan.dicks＠gmail.com -
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