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

[Wilko Bulte]

Wild guess here, this sounds to me like a coil "whistling". Maybe there is an inductor or transformer  that lost its potting compound, or has somehow come loose from its fittings?

best,
Wilko

> On 10 Sep 2023, at 21:24, David Kirkby via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> 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
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe send an email to time-nuts-leave at lists.febo.com