[time-nuts] HP5370 power supply measurements
bob at evoria.net
Fri Jul 15 01:00:27 EDT 2016
I am very interested in your 5370 power conversion. Can you give us any more information as to the model number of the buck regulators you used and where you got them. Did you run into any problems? Did you make any notes or drawings?
GFS GPSDO list:
From: Rami Vainio <rami.vainio at gmail.com>
To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
Sent: Wednesday, July 13, 2016 10:19 AM
Subject: Re: [time-nuts] HP5370 power supply measurements
Hello, I did SMPS mod to my 5370. If I remember correctly, consumption
of +5V was ~5A and -5,2V ~7A. I removed original +5/-5,2V linear
regulators and replaced them with step-down converters. -5,2V side I did
float original diode bridge and capasitor and put smps module to
positive rail. I also removed original prom card and put eprom directly
to cpu card. Power consumption dropped to close 110W. There was no
visible performance change after mod.
Rami Vainio OH2LIY
Email : rami.vainio at gmail.com
Phone : +358 40 505 8085
On 11.7.2016 21:46, Poul-Henning Kamp wrote:
> Inspired by the recent thread about power trouble, I spent an hour
> to actually measure why the HP5370 gets so warm as it does.
> I'm running on 230VAC here, with the 230/240VAC power setting.
> With A6 and A7 removed and turned off: PAC= 4.2 W
> That is the loss in the transformer and rectifiers, since the "power"
> switch on the HP5370 really isn't that.
> Turning it on, PAC= 19.9W
> So the fan uses 15.7W. (it's also noisy, I should find a replacement)
> I also measured the four unregulated DC voltages:
> -20V -> 28.9V
> -10V -> 13.4V
> +10V -> 13.4V
> +20V -> 28.9V
> Inserting A6 does not change the OFF state PAC measurably.
> Turning on however: PAC = 140 W
> -20V -> 27.5V
> -10V -> 10.9V
> +10V -> 11.9V
> +20V -> 27.1V
> +15V -> 14.99V
> -15V -> 15.04V
> +5V -> 5.05V
> -5.2V-> 5.4V
> +10V -> 10.0009V
> -20V -> 123mV ripple
> -10V -> 2.02V ripple
> +10V -> 960mV ripple
> +20V -> 312mV ripple
> The unregulated busses are still waay over what the schematics
> would have you belive (10/20V). The ripple on the -10V seems
> pretty high, but the four electrolytic capacitors seem healthy
> Next I tried measuring the current on the four regulated voltages,
> which all have short-circuit measuring resistors:
> A6 pin 5- 6 188mV, 0.07R 3% -> 2.68A +5V
> A6 pin 7- 8 498mV, 0.07R 3% -> 7.11A -5.2V
> A6 pin 9-10 109mV, 0.4R 1% -> .2725A +15V
> A6 pin 11-12 55mV, 0.4R 1% -> .1375A -15V
> Since I measured this on the bottom of the motherboard, the contact
> and PCB trace resistance to/on A6 is also included so these currents
> are high estimates.
> Measuring with a clamp milliamp-meter instead I find:
> +5V -> 2.2A
> -5.2V -> 5.5A
> Doing the math:
> Brutto Netto
> Trafo: 4.2 W 4.2 W
> Fan: 15.7 W 15.7 W
> OCXO: 14.0 W 14.0 W Netto Brutto
> -20: 3.8 W 2.1 W 2.1 W 3.8 W
> -10: 60.0 W 29.0 W 29.0 W 60.0 W
> +10: 31.9 W 13.4 W 13.4 W 31.9 W
> +20: 7.4 W 4.1 W 4.1 W 7.4 W
> 137.5 W 82.5 W 48.6 W 103.1 W
> Modern efficient DC/DC converters should therefore be able to
> reduce the PAC by about 50W or one third.
> I tried load-testing the unregulated busses, and it looks like all
> four of them can be loaded up to about 5A individually before the
> voltage falls out of spec (10/20 V)
> So I've been playing around with KICAD and come up with a design
> with three Traco TEN40WIR DC/DC converters (2x2411 + 2423) running
> off the +/- 10V rails, and I'm seriously tempted to try order a
> PCB just to try it out...
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