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

Wed Sep 13 19:13:33 UTC 2023

hello Helmuth,

I just dismantled my MPS power supply for you.

Pins 6-7 are 1.7 Î©
Pins 8-9 are 0.5 Î©

Unloaded 8-9 carry 24.8 VAC
Unloaded 6-7 carry 36.1 VAC 

In both cases I measured direct on the transformer, without desoldering the wires. Resistance values are close enough to your measurements I would think. 

AC voltages seem reasonable for the 20.5 VDC the system uses. The 36 VAC is for the heater if I remember correctly. 

The mains coil with the 240V range selected on the IEC inlet is 9.7 Î© measured at the actual inlet. 

Currents I cannot measure, I would need an extender for the special DIN41612 connector variant (which I do not own). And my MFS has 2x MBF and an MPC in addition to the MRK (FRK-HLN in this case) so the current measured would be different anyway. Current drawn by the MRK is in the manual I think. 

I unfortunately I do not have a schematic for the MPS. 

Picture of the xformer is attached 

Hope this helps,

Wilko

> On 13 Sep 2023, at 19:59, jung.schorndorf--- via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> ï»¿I am also a lover of hp measurement technology, but I do not have the described frequency and time standard 58503A/B of hp or Symmetricom.
> My frequency standards (also rubidium) come from DATUM-Symmetricom, Meinberg and other manufacturers.
> 
> To the problem described here in the forum I can give from my experience the tip on the power transformer.
> 
> I think the time-nuts fans also have many devices and may be able to give me information on my DATUM-Symmetricom device.
> 
> Hello Willo,
> yes, my transformer has 230V winding interruption on primary side. Secondary side pin 6-7 has 1.6 ohms, pin 8-9 has 0.3 ohms.
> To find the right transformer, I need the low-voltage AC voltages and currents. If your power supply is open again, I ask for measurements or schematic information.
> Thanks
> 
> MfG
> Helmut
> 
> 
> -----UrsprÃ¼ngliche Nachricht-----
> Von: Wilko Bulte via time-nuts <mailto:time-nuts at lists.febo.com> 
> Gesendet: Dienstag, 12. September 2023 22:23
> An: Discussion of precise time and frequency measurement <mailto:time-nuts at lists.febo.com>
> Cc: Wilko Bulte <mailto:wkb at xs4all.nl>
> Betreff: [time-nuts] Re: Power supply buzzing in HP 58503A GPS receiver.
> 
> hello Helmut,
> 
> Are you 100% sure the transformer is indeed dead? And, in other words, it is not a problem in the DC part 'behind' the transformer like a dead bridge rectifier, bulk cap or pass transistor? Are you certain you have open or short windings on the transformer?
> 
> The MPS transformer in my MFS system does not look better than yours, also some corrosion etc. That is not a reason perse for worry, mine works just fine. 
> 
> Just my â‚¬0,02..
> 
> MfG,
> Willo
> 
>> On 12 Sep 2023, at 21:29, jung.schorndorf--- via time-nuts <mailto:time-nuts at lists.febo.com> wrote:
>> 
>> ï»¿Hello time and frequency standard owners,
>> 
>> a similar problem, tap Power Transformer ...
>> 
>> my power supply MPS in the device MFS (Modular Frequency Systems) from EFRATOM-DATUM_SYMMETRICOM has plagued me with a hum noise
>> for many months. When it stopped working and I opened it, the power transformer turned out with a turn damage (photo) and totally corroded - in laboratory conditions!
>> I can also operate the device externally with 24V DC. However, I would like to replace the unavailable original transformer,
>> but have not seen any transformer data (U, I) because missing documents. Because winding interruption I can not measure it either.
>> In the data sheets I only find different DC data (20.5V DC, 23-33V DC, 40 W, 55 W ??).
>> The transformer had 2 AC outputs on the secondary side.
>> I have only a few inserts and do not need the theoretical 200 VA max. power.
>> Does anyone in the US still have circuits? The German branch has nothing more.
>> 
>> Thanks for info
>> Helmut
>> 
>> 
>> 
>> 
>> -----UrsprÃ¼ngliche Nachricht-----
>> Von: Adrian Godwin via time-nuts <mailto:time-nuts at lists.febo.com> 
>> Gesendet: Montag, 11. September 2023 10:10
>> An: Discussion of precise time and frequency measurement <mailto:time-nuts at lists.febo.com>
>> Cc: Adrian Godwin <mailto:artgodwin at gmail.com>
>> Betreff: [time-nuts] Re: Power supply buzzing in HP 58503A GPS receiver.
>> 
>> I don't have a 58503A but I do have some RFTG-u which I understand to be
>> quite similar. I'm not sure if that extends to the power supply
>> architecture. Do they just have an integral mains power supply before a
>> Lucent DC-DC converter ?
>> 
>> I had one fail due to a tantalum capacitor downstream of the DC-DC
>> converter. It didn't shut down the DC-DC but it did cause it to take a
>> heavy incoming current resulting in the literal melting (and subsequent
>> mains breaker cutout) of a cheap power brick that was being used to provide
>> 24V.
>> 
>> So, the mains part of the supply might be running at an overcurrent without
>> shutting down.
>> 
>> Replacing the tant (and the power brick) fixed it without any other damage.
>> 
>> 
>>> On Mon, Sep 11, 2023 at 5:31â€¯AM Ed Marciniak via time-nuts <
>>> mailto:time-nuts at lists.febo.com> wrote:
>>> 
>>> I donâ€™t have one of those units, but switching power supplies under
>>> certain load conditions can have subharmonic oscillations that happen to
>>> fall in the audible frequency range. Absent an overload from a shorter
>>> capacitor or similar, Iâ€™d take a hard look at whether there are capacitors
>>> that no longer meet their ESR specifications and/or have cold solder joints
>>> effectively removing them from the circuit.
>>> ________________________________
>>> From: Wilko Bulte via time-nuts <mailto:time-nuts at lists.febo.com>
>>> Sent: Sunday, September 10, 2023 3:57:06 PM
>>> To: Discussion of precise time and frequency measurement <
>>> mailto:time-nuts at lists.febo.com>
>>> Cc: Wilko Bulte <mailto:wkb at xs4all.nl>
>>> Subject: [time-nuts] Re: Power supply buzzing in HP 58503A GPS receiver.
>>> 
>>> 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 <
>>> mailto:time-nuts at lists.febo.com> wrote:
>>>> 
>>>> ï»¿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: mailto: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
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>> <MPS_8.jpg>
>> <MPS_1.jpg>
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