[time-nuts] Power supply buzzing in HP 58503A GPS receiver.

[David Kirkby]

After about 6 months of being powered off, I switched on my GPS receiver
yesterday. The PSU is buzzing quite loudly. Sound file at

https://www.kirkbymicrowave.co.uk/noisy-PSU-in-HP-58503A-GPS-time-and-frequency-standard-recorded-10th-Sempember-2023.m4a

I thought that one of the 100 uF 400 V capacitors after the rectifier might
be bulging, although I was unsure. The capacitance measures okay, and the
ESR is below that of anything I can buy that will physically fit. Same for
the 47 uF 400 V capacitor. These were both measured out of circuit, using
an HP 4284A LCR meter at 120 Hz. I chose that, despite the fact that we
have 50 Hz mains here in the UK, as data normally seems to be provided on
capacitors at 120 Hz.

Has anyone experienced this before? I believe that someone wrote here, or
might have been elsewhere, that the GPS receiver was pushing one of the
supplies to the limit, and another one was not loaded enough. I know there
was some mention of converting it to run from a linear supply, although I
think that would be physically larger, so not fit in the case.


-- 
Dr David Kirkby Ph.D
Kirkby Microwave Ltd
Email: drkirkby at kirkbymicrowave.co.uk
Web: https://www.kirkbymicrowave.co.uk/
Telephone 07910 441670 (UK) or +44 7910 441670 (international)
Registered in England and Wales, company number 08914892.
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT