0-500V 200mA tube based powersupply 1965 - Page 1
Forum section: electronics / projects

author: oz2cpu
author_rank: Frequent Contributor
timestamp: March 07, 2025, 08:55:53 am
content: i spend the last few days playing with this one, a fantastic tube based DC powersupply 0-500 200mAit was made by Philips in Sweden, i was able to get super performance out of it, using tested and matched tubes with like new spot on specifications.if you are into tubes ?you might find this one interesting :https://youtu.be/tKLCnDrNYmo

author: BILLPOD
author_rank: Frequent Contributor
timestamp: March 07, 2025, 02:25:18 pm
content: Great Job, Tom.......as usual. I was graduating from high school when that PSU was built.Thanks for showing it

author: Kleinstein
author_rank: Super Contributor
timestamp: March 07, 2025, 04:39:18 pm
content: This is quite some power from what looks like straight linear regulation.

author: TimFox
author_rank: Super Contributor
timestamp: March 07, 2025, 05:03:13 pm
content: I have a couple of Kepco power supplies with similar specs, using discrete transistor feedback amplifiers controlling paralleled pass tubes (6550s or 6L6s). I also have a late Heathkit with a 6AU6 fb amp, gas reference tube, and parallel 6L6GCs. Since 6550s are expensive, I replaced them with 6BG6s (rewiring sockets and adding plate caps), using some late Phillips ECG tubes that had “GC” guts (plate rating of 6L6GC).For a project, I built a power supply regulator with a 6Y6 pass tube controlled by a 6SH7 pentode with a gas tube in its cathode. After fixing a high-frequency parasitic oscillation (adding a stopper resistor in the 6SH7 plate lead), I looked carefully at the output and saw a strange low-level periodic signal, line-synchronizous, at a subharmonic of 60 Hz, that resisted my tweaks to the circuit and drove me to distraction. Seeing my distress, my wife suggested that I was picking up something, to which I replied that the only two units turned on were my CRO and the soldering iron. The problem disappeared when I shut the soldering station off. Apparently, the zero-crossing control had gone into a limit cycle at 10 Hz, synchronized to the line, and the current draw was affecting the heater voltage of the 6SH7, inducing a periodic offset variation.

author: oz2cpu
author_rank: Frequent Contributor
timestamp: March 08, 2025, 04:57:55 pm
content: exactly Kleinstein, it is lenear, all EL34 are cathode followers,there is a switch to select between 0-250V or 0-500V output range.The schematic is drawn a little bit hard to read,but the 4 large diodes, are not in a bridge, but are parallel 2 and 2,the two caps C1 C2 are in series, this is a voltage doubler,this switch S2 selects anode voltage from 300 or 600Vthe worst thing you can do is select the high range,then dial low output voltage, and load it fully,there is nothing that prevents this, and the outcome will be overloaded tubes,so i would assume correct usage is carefully explained in the manual,i dont have the manual, only the schematic was found scanned and shared with me, so i put it online also.

author: trobbins
author_rank: Frequent Contributor
timestamp: March 09, 2025, 01:29:37 pm
content: I asked my 'Philips' colleague in Netherlands about the GM445B and he couldn't locate any info from his local Philips, and yes he said it was made in Sweden. He did send me the manual for the PE1531 (500V 300mA), which may have similarities. There are a few regulated pentode mode supplies that may be similar - in Australia we even had one (BWD 210B). PM me for the PE1531 manual.

author: jonpaul
author_rank: Super Contributor
timestamp: March 09, 2025, 01:54:42 pm
content: Well these lab suppplies were common in the 1950s..1970, in USA;Based on the classic 1935 (!) RCA vacuum tube manualBy 1950s Heathkit made several variations. See PS-1https://people.ohio.edu/postr/bapix/TSM_12-2019_article.htmFor A walk down memory lane.....My 1960s (high school) 0-400V 250 mA tube lab supply. Based on the Heathkit design.Metered, thyratron/mercury wetted relay over voltage/over current meter-relay protection, massive CRT TV transformer,Used 3 x 6BQ6 beam power tubes for series pass, 12AX7 amplifier, 2 X OD3 150V argon voltage regulators.large Rotron fan cooling of the pass tubes, with a thermostat switch to turn on fans as needed.weight ~ 20 kG, STILL WORKING!Your thoughts appreciated.Have an absolutely fantastic day !Jon

author: TimFox
author_rank: Super Contributor
timestamp: March 09, 2025, 02:56:41 pm
content: Dymo labels before DRM!