hello Helmuth, I just dismantled my MPS power supply for you. Pins 6-7 are 1.7 Ω Pins 8-9 are 0.5 Ω 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 Ω 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@lists.febo.com> wrote: > > 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 > > > -----Ursprüngliche Nachricht----- > Von: Wilko Bulte via time-nuts <mailto:time-nuts@lists.febo.com> > Gesendet: Dienstag, 12. September 2023 22:23 > An: Discussion of precise time and frequency measurement <mailto:time-nuts@lists.febo.com> > Cc: Wilko Bulte <mailto:wkb@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 €0,02.. > > MfG, > Willo > >> On 12 Sep 2023, at 21:29, jung.schorndorf--- via time-nuts <mailto:time-nuts@lists.febo.com> wrote: >> >> 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 >> >> >> >> >> -----Ursprüngliche Nachricht----- >> Von: Adrian Godwin via time-nuts <mailto:time-nuts@lists.febo.com> >> Gesendet: Montag, 11. September 2023 10:10 >> An: Discussion of precise time and frequency measurement <mailto:time-nuts@lists.febo.com> >> Cc: Adrian Godwin <mailto:artgodwin@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 5:31 AM Ed Marciniak via time-nuts < >>> mailto:time-nuts@lists.febo.com> wrote: >>> >>> I don’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, I’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@lists.febo.com> >>> Sent: Sunday, September 10, 2023 3:57:06 PM >>> To: Discussion of precise time and frequency measurement < >>> mailto:time-nuts@lists.febo.com> >>> Cc: Wilko Bulte <mailto:wkb@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@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: mailto:drkirkby@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 -- mailto:time-nuts@lists.febo.com >>>> To unsubscribe send an email to mailto:time-nuts-leave@lists.febo.com >>> _______________________________________________ >>> time-nuts mailing list -- mailto:time-nuts@lists.febo.com >>> To unsubscribe send an email to mailto:time-nuts-leave@lists.febo.com >>> _______________________________________________ >>> time-nuts mailing list -- mailto:time-nuts@lists.febo.com >>> To unsubscribe send an email to mailto:time-nuts-leave@lists.febo.com >> _______________________________________________ >> time-nuts mailing list -- mailto:time-nuts@lists.febo.com >> To unsubscribe send an email to mailto:time-nuts-leave@lists.febo.com >> <MPS_8.jpg> >> <MPS_1.jpg> >> _______________________________________________ >> time-nuts mailing list -- mailto:time-nuts@lists.febo.com >> To unsubscribe send an email to mailto:time-nuts-leave@lists.febo.com > _______________________________________________ > time-nuts mailing list -- mailto:time-nuts@lists.febo.com > To unsubscribe send an email to mailto:time-nuts-leave@lists.febo.com > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-leave@lists.febo.com