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Discussion of precise time and frequency measurement

HP Z3816A – no 10 MHz output / need info on feed point

David Radecker

Sat, Nov 29, 2025 5:01 PM

Hi everyone,

I’m currently working on an HP Z3816A that originally had a faulty OCXO.
I'm trying to repair the oscillator itself now, but I’m running into a problem: on my board the RF-OUT pin of the OCXO is completely unconnected - no trace, no jumper, nothing.

The unit should double 5 MHz to 10 MHz somewhere on the board, but I’m unsure where exactly the feed point is located and how the OCXO is normally wired into the chain.

I found the modification blog on xertech.net, but I did not perform that mod - I only used the photos for reference. Unfortunately, I can’t see the OCXO area from the bottom side.

Does anyone here have bottom-side photos of the OCXO area, or information on where the RF-OUT pin is normally routed?
Any hints or images would be extremely helpful.

Thanks in advance!
David

Hi everyone, I’m currently working on an HP Z3816A that originally had a faulty OCXO. I'm trying to repair the oscillator itself now, but I’m running into a problem: on my board the RF-OUT pin of the OCXO is completely unconnected - no trace, no jumper, nothing. The unit should double 5 MHz to 10 MHz somewhere on the board, but I’m unsure where exactly the feed point is located and how the OCXO is normally wired into the chain. I found the modification blog on xertech.net, but I did not perform that mod - I only used the photos for reference. Unfortunately, I can’t see the OCXO area from the bottom side. Does anyone here have bottom-side photos of the OCXO area, or information on where the RF-OUT pin is normally routed? Any hints or images would be extremely helpful. Thanks in advance! David

timeok@timeok.it

Sat, Dec 13, 2025 12:39 PM

Dear colleagues,

I need help repairing a Caesum Datum FTS4065B. The problem seems to be the -15V power supply. Unfortunately, I couldn't find any wiring diagrams, and the low-voltage regulator board has a single 50-pin connector. Its test points are for +5 and +24V only, so it's not even clear whether the regulator is on this board. Does anyone have the wiring diagram for this wonderful standard?

Thanks, Luciano

Luciano P. S. Paramithiotti
timeok@timeok.it
www.timeok.it

Da "David Radecker via time-nuts" time-nuts@lists.febo.com

A time-nuts@lists.febo.com

Cc "David Radecker" david.radecker@gmail.com

Data Sat, 29 Nov 2025 18:01:22 +0100

Oggetto [time-nuts] HP Z3816A – no 10 MHz output / need info on feed point

Hi everyone,

I’m currently working on an HP Z3816A that originally had a faulty OCXO.
I'm trying to repair the oscillator itself now, but I’m running into a problem: on my board the RF-OUT pin of the OCXO is completely unconnected - no trace, no jumper, nothing.

The unit should double 5 MHz to 10 MHz somewhere on the board, but I’m unsure where exactly the feed point is located and how the OCXO is normally wired into the chain.

I found the modification blog on xertech.net, but I did not perform that mod - I only used the photos for reference. Unfortunately, I can’t see the OCXO area from the bottom side.

Does anyone here have bottom-side photos of the OCXO area, or information on where the RF-OUT pin is normally routed?
Any hints or images would be extremely helpful.

Thanks in advance!
David

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Dear colleagues, I need help repairing a Caesum Datum FTS4065B. The problem seems to be the -15V power supply. Unfortunately, I couldn't find any wiring diagrams, and the low-voltage regulator board has a single 50-pin connector. Its test points are for +5 and +24V only, so it's not even clear whether the regulator is on this board. Does anyone have the wiring diagram for this wonderful standard? Thanks, Luciano Luciano P. S. Paramithiotti timeok@timeok.it www.timeok.it Da "David Radecker via time-nuts" time-nuts@lists.febo.com A time-nuts@lists.febo.com Cc "David Radecker" david.radecker@gmail.com Data Sat, 29 Nov 2025 18:01:22 +0100 Oggetto [time-nuts] HP Z3816A – no 10 MHz output / need info on feed point Hi everyone, I’m currently working on an HP Z3816A that originally had a faulty OCXO. I'm trying to repair the oscillator itself now, but I’m running into a problem: on my board the RF-OUT pin of the OCXO is completely unconnected - no trace, no jumper, nothing. The unit should double 5 MHz to 10 MHz somewhere on the board, but I’m unsure where exactly the feed point is located and how the OCXO is normally wired into the chain. I found the modification blog on xertech.net, but I did not perform that mod - I only used the photos for reference. Unfortunately, I can’t see the OCXO area from the bottom side. Does anyone here have bottom-side photos of the OCXO area, or information on where the RF-OUT pin is normally routed? Any hints or images would be extremely helpful. Thanks in advance! David _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-leave@lists.febo.com