Input stage of HP 5326 frequency counter
Sverre Holm (LA3ZA)
I have an HP 5326B counter from the seventies that suffers from low
sensitivity, about 50 mV rms rather than 5 mV rms as the specs say. The
frequency range from 0 -50 MHz is fine, actually it is OK up to about 70
MHz. I have tried to understand the input stage in order to figure out where
the loss occurs. There I came across an integrated circuit with 6 pins in a
TO39 size can (same as a 2N1711, except 6 pins). Its designation is 5-334
7038 and it has a symbol that I think is that of National Seminconductor
(looks like an N on top of an S).
Does anyone know anything about this IC, or better yet are familiar with the
input board of this counter (type no of board
is 05326-60003).
Thanks a lot
Sverre
Oslo, Norway
____________________________________
http://www.qsl.net/la3za
Tom Bruhns
you can find an old HP crossreference list, look up an 1855-0334.
Cheers,
Tom -- K7ITM
"Sverre Holm \(LA3ZA\)" <svh...@online.no> wrote in message news:<Pqco7.16326$1T5.1...@news1.oke.nextra.no>...
Tom Dunn
\(LA3ZA\)" <svh...@online.no> wrote:
>
>I have an HP 5326B counter from the seventies that suffers from low
>sensitivity, about 50 mV rms rather than 5 mV rms as the specs say. The
>frequency range from 0 -50 MHz is fine, actually it is OK up to about 70
>MHz. I have tried to understand the input stage in order to figure out where
>the loss occurs. There I came across an integrated circuit with 6 pins in a
>TO39 size can (same as a 2N1711, except 6 pins). Its designation is 5-334
>7038 and it has a symbol that I think is that of National Seminconductor
>(looks like an N on top of an S).
>
>Does anyone know anything about this IC, or better yet are familiar with the
>input board of this counter (type no of board
>is 05326-60003).
>
>Sverre
>Oslo, Norway
>____________________________________
>http://www.qsl.net/la3za
As mentioned in Tom Burns post Part is a dual N channel FET. The part was
made by Siliconix. Siliconix part number was DN377. This information is
from 5326 manual. The HP cross reference does not show a cross for this
part. In worse case you could put two seperate N channel FETs in place of
the dual. Tom WB6IQD
Sverre Holm (LA3ZA)
traced the circuit and I have started to doubt that there is anything wrong
with the input stage after all.
The amplifier consists of a differential JFET input stage followed by two
more NPN transistor differential stages that goes into a differential
common-base stage. This is where the voltage gain occurs. After that follows
a differential Schmitt trigger. Now in my counter, everything seems to be
working fine, all DC voltages are balanced correctly in the differential
stages and the signal can be traced from stage to stage.
What confuses me is that I can read from the HP product description on
http://www.qsl.net/la3za/HP5326a.pdf that the input sensitivity is 5 mV,
while my counter has a sensitivity of 50 mV uniformly from audio to 50 MHz.
If you have the manual, maybe the value for sensitivity can be verified?
Sverre
____________________________________
73 de LA3ZA
http://www.qsl.net/la3za
"Tom Dunn" <du...@its.caltech.edu> skrev i melding
news:dunnt-17090...@dhcp-40-143.caltech.edu...
Jim Adney
>What confuses me is that I can read from the HP product description on
>http://www.qsl.net/la3za/HP5326a.pdf that the input sensitivity is 5 mV,
>while my counter has a sensitivity of 50 mV uniformly from audio to 50 MHz.
>If you have the manual, maybe the value for sensitivity can be verified?
Is there any chance that the 50mV you think you're inputting is really
more like 5mV? Got a good calibrated instrument for measuring?
Properly terminated line?
-
-----------------------------------------------
Jim Adney jad...@vwtype3.org
Madison,Wisconsin USA
-----------------------------------------------
Dan Rae
Sverre,
Don't know where you got the 5 mV from; my 1973 hp catalog lists the sensitivity
as 0.1 volt rms sine wave.........
Sverre Holm (LA3ZA)
http://www.electronique-diffusion.fr/Accueil/Presentation/Gentilly/Mesure/Fr
equencemetre/5326a.pdf
http://www.electronique-diffusion.fr/Accueil/Presentation/Gentilly/Mesure/Fr
equencemetre/5326c.pdf
and http://www.helmut-singer.de/stock/1305662250.html, where the last
sentence says "Beide Eingangskanäle besitzen eine Empfindlichkeit bis
hinunter zu 5 mV." = Both input channels have a sensitivity better than 5
mV.
However, your number is right, my audio and RF-generators indicate 50 mV rms
sensitivity for inputs A & B and 30 - 40 mV rms sensitivity on channel C. So
I guess that is how it should be. It confuses me still to see the
information in the brochures quoted above.
So that's what got me on the search for the extra 20 dB of sensitivity,
which would be nice to have, but that I never found ....
Thanks for all help from various people in looking up their manuals.
Sverre
____________________________________
73 de LA3ZA
http://www.qsl.net/la3za
"Dan Rae" <ra...@ix.netcom.com> skrev i melding
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