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 Voltages: -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 enough. 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... -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.