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National, comparator with strobe?

Hello Folks,

Does anyone know a comparator with strobe function from National? It has this writing on the DIL body:

1st line: /025P (plus National Semiconductor logo) 2nd line: 1826-0210

It is in a HP4191A and at least 20 years old in terms of production. The design of this instrument dates back to around 1980 so this comparator must have been around since then. Worst case it's one of those custom deals. Even my 1982 databook doesn't carry it :-(

Anyway, the service data is rather skimpy here but from the timing diagrams in there it is not supposed to signal any zero crossing while "STROBE" is high. However, it does. Basically it issues a zero crossing whenever strobe occurs so possibly it's busted.

Probably the way HP would find out is swap the respective board. Unfortunately I don't have that luxury here.

Regards, Joerg

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Reply to
Joerg
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If you have the manual, post the appropriate section of the schematic to abse and I'll look through my databooks for anything that matches. What are the supply voltages/logic levels?

John

Reply to
John Larkin

The 1826-0210 is an LM361N

Reply to
DaveM

The 1826-0210 is a National LM361N

--
Dave M
MasonDG44 at comcast dot net  (Just substitute the appropriate characters in the 
address)

Some days you're the dog, some days the hydrant.
Reply to
DaveM

Hello John,

Thank you. I just posted it. It's the usual +/-12V and also is fed +5V logic supply via pin 14 (which is kind of unusual).

Regards, Joerg

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Reply to
Joerg

Sounds like Dave has nailed it.

John

Reply to
John Larkin

Hello Dave,

Thank you! Great. Now I just have to figure out the strobe pin mystery. A NS data sheet from 1999 says the output is low when the strobe pin is pulled which is what the inner circuit looks like, the one in the 1982 databook conveniently says nothing, and the HP4191A manual seems to say the opposite. But that doesn't surprise me anymore.

Regards, Joerg

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Reply to
Joerg

Hello John,

Indeed he did. Besides the strobe pin scenario in the analyzer's timing diagrams not corroborating with the 361's data sheet I found that they were quite brazen with decoupling. 100ohms to each supply pin and only one 33uF electrolytic per pin. All neatly in one row and, gasp, with traces going from the caps to the pins.

Regards, Joerg

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Reply to
Joerg

It's a 20 ns comparator. What's the rush?

Somehow the old HP schematics (and the gear, too!) looked clumsy compared to the much more graceful, color-coded Tek stuff. And once in a while you got a bonus tekdoodle. Nobody ever accused HP of whimsey.

John

Reply to
John Larkin

Hello John,

True, it's slow. But electrolytics tend to dry up over the years and some stuff might develop a tendency to become instable if the supply veers towards mushiness. 0.1uF caps would have been nice. Oh well, if I can fix the machine maybe I add some.

Didn't find a doodle yet but this manual seems to have authors from Yokogawa. "A short precharge, made by..." and the occasional missing "the" or "a".

The tough challenge here is what to make of timing diagrams when a state changes while an enabling signal is low and the data sheet of the part indicates that this cannot be so. Then you end up reverse engineering the thing just to be able to see how it really operates, or used to operate.

Regards, Joerg

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Reply to
Joerg

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