[time-nuts] HP-58503A

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 1 January 2015 at 17:03, Andy Bardagjy <andybardagjy at gmail.com> wrote:
> Sounds like the GPS receiver is hosed. I think there are two different receivers used in the 58503a, unfortunately I'm away from my lab, otherwise I could check mine. It is a standard part, and may be available on the surplus market.
>
> Before replacing, I'd check the usual suspects, power supply health (look for failed electrolytics) and re-seat the gps board to board connector.
>
> Happy to measure things on my 58503a.

The fact it originally failed with errors indicting the GPS receiver
was not ok (nt Power- OK, OCXO- OK, EFC-OK GPS RCV-err. I, but later
he can't communicate with the 58503A over RS-232, to me indicates the
problem is not likely to be the just (if at all) the GPS receiver.

As you say, power supply is a possible problem.

I have a 58503A here that has a problem. Sometimes when power is first
applied, the "Alarm" light stays on, and the log show power supply
voltage errors. Yesterday I must have switched the thing on/off about
30 times before I managed to get the "Alarm" light to stay on. At the
time I had a handheld DVM connected to the +15 V rail with the "peak
hold" mode enabled. At least according to the handheld DVM, the +15 V
rail was normal, so either the transient is too short for my handheld
DVM to see, or the 85050A is reporting data voltage data incorrectly.
Both are fairly like I suspect.

I noticed a *very* slight bulge at the top of on a 100 uF, 400 V
capacitor on the switch mode power supply.  For various reasons, I am
not going to change that cap now, but obviously a failed cap could
cause this sort of problem.

Dave