[time-nuts] HP 3325B Function Generator and GPSbased frequencycontrol

[Greg Burnett]

Across the life-span of the HP 3325A, the following changes were
incorporated:

1. They removed the sockets for power supply regulator transistors (instead
soldering the leads right to the board) for better reliability.

2. They re-designed the power supply board layout in order to put more space
between a "hot" AC mains trace and a grounded mounting screw (safety issue).

3. They changed the ribbon cables' connectors from "tinned" to gold-plated
for better reliability. (They changed the associated ribbon cables for same
reason.)

4. They replaced the old high-profile yellow attenuator relays with the
low-profile black Omron relays -- this was a big improvement in attenuator
reliability.

5. They redesigned the controller/HPIB board. (Both old and new boards
worked equally well, but the new board was more simple, with less number of
IC's, as I remember.)

Back in the eighties and nineties, whenever a 3325A came to HP for any
repair, items 1 through 3 (above) were routinely updated (e.g., new power
supply board, new ribbon cables & connectors, etc. were installed). Also,
many times the old attenuator board was replaced with the new one. All
together, many older 3325A's therefore have the newer features inside.

By the time the 3325B was introduced, all the above features were included
in production, and the controller/HPIB board (and its firmware) were further
refined and stream-lined. A few additional programming commands were added.

Bottom line: If you have a fully updated "A", your unit is just about every
bit as good as the "B" version. Otherwise your "A" version might be less
reliable, with some intermittent digital resets to the turn-on state, and
have intermittent output levels (if you still have the old attenuator board
with the big yellow relays).

Greg


----- Original Message ----- 
From: "John Ackermann N8UR" <jra at febo.com>
To: "Discussion of precise time and frequency measurement"
<time-nuts at febo.com>
Sent: Tuesday, July 11, 2006 8:39 AM
Subject: Re: [time-nuts] HP 3325B Function Generator and GPSbased
frequencycontrol


I've always been curious about the 3325A vs. B -- there is more price
spread between those two than just about any other HP A vs. B model.
What's the difference between them, and is it worth anything like that
much (obviously, Mike doesn't think so :-) ).

I've been happy with my A model, though it often fails amplitude
calibration on powerup.  Waiting a few seconds and then running the cal
always works, though.

John
----

Mike Feher wrote:
> Seems like a lot of money to pay for one. I have been using an HP 3325A
for
> about 25 years and like it very much. I bought it brand new from HP for
the
> company I worked, where I was director of engineering. After I resigned,
to
> pursue greener pastures, they eventually closed down their hardware
> capability and operations and offered me the entire laboratory and
inventory
> which then I purchased personally. I would recommend you getting the "A"
> version for about one fifth of the price of that "B" model, unless, you
have
> an overwhelming desire to get the "B" for some special reason. Option 001
> provides the high accuracy ovenized reference and it does not look like
the
> one on ebay has that option. Normally they would use a TCXO. Regardless,
> since you will be using an external reference it really does not matter.
The
> "A" also accepts an external reference and I run my off of a local
Rubidium.
> 73 - Mike


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