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Hi all,
I've got a dead 1820-0090 IC from an 5216A counter and am looking for
a common replacement if it exists.
Its function is "buffer storage" and it sits between a decade counter
& a decoder driver chip.

In my search I came across
which has heaps of HP semicond/IC cross reference data but
unfortunately doesn't include the 1820-0090.

Cheers
Ian Du Rieu

Hello,

Fedlog says it is a TTL 4 bit storage register. No
JEDEC P/N cross reference given, but it is probably
74xx series. It is also the same as an 1820-0091 and
1820-0116.

Regards,

Jim

--- iandurieu <idurieu@...> wrote:

Hi all,
I've got a dead 1820-0090 IC from an 5216A counter
and am looking for
a common replacement if it exists.
Its function is "buffer storage" and it sits between
a decade counter
& a decoder driver chip.

In my search I came across

which has heaps of HP semicond/IC cross reference
data but
unfortunately doesn't include the 1820-0090.

Cheers
Ian Du Rieu

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--- In hp_agilent_equipment@..., Jim Reese <nfeinc@y...>
wrote:

Hello,

Fedlog says it is a TTL 4 bit storage register. No
JEDEC P/N cross reference given, but it is probably
74xx series. It is also the same as an 1820-0091 and
1820-0116.

Regards,

Jim

Hi Jim,

Thanks. Functionally it looks a lot like a 7475 except that the
pinouts don't match.

Cheers
Ian Du Rieu

--- In hp_agilent_equipment@..., "iandurieu"
<idurieu@h...> wrote:

--- In hp_agilent_equipment@..., Jim Reese <nfeinc@y...>
wrote:

Hello,

Fedlog says it is a TTL 4 bit storage register. No
JEDEC P/N cross reference given, but it is probably
74xx series. It is also the same as an 1820-0091 and
1820-0116.

Regards,

Jim

Hi Jim,

Thanks. Functionally it looks a lot like a 7475 except that the
pinouts don't match.

Cheers
Ian Du Rieu

Hi all,
I made an adaptor for a 7475 to 1820-0090 to fix the pinouts.
The enable pin's logic is inverted so a 1 transistor inverter fixed
that.
It looks like the 1820-0090 is RTL. HP's drive circuit was a 360pF
buffered by an emitter follower without a pulldown. 1 x TTL load
stuffed it up. It was already driving 7 other 1820-0090 chips.
Adding the transistor inverter solved the loading gremlin.

If anyone is interested in the fine details I have a .GIF file
detailing the mods.

Cheers
Ian Du Rieu