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" <[EMAIL PROTECTED]> To: "Discussion of precise time and frequency measurement" <time-nuts@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 _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts