[GreenKeys] 120VDC power supply noise?

[wa2hwj at att.net]

Greenkeyers...

I passed this important information to Eugene:

"The only reason transformers hum is because they don't know the words!"

Jack WA2HWJ

NNNN



-------------- Original message from Don Robert House <packard42 at gmail.com>: -------------- 


> Eugene, 
> 
> With the Teletypes running you probably will not hear the hum. I 
> have one of those supplies mounted at our shop machine in the 
> museum. Like all of these vintage 120 - 130 vdc supplies (and the 
> one aboard ship) they all made/make some noise. Methinks new 
> technology has spoiled you ;-) 
> 
> Don 
> 
> 
> 
> On Oct 10, 2005, at 7:34 AM, Eugene Hertz wrote: 
> 
> 
> > Hello, Harvey! Thanks a bunch for some excellent troubleshooting/ 
> > analysis ideas. I will try some of them as soon as possible. The 
> > only other few things I can tell you are a) output is rated at 80ma 
> > b) I disconnected both secondaries (one to the rectifier and one to 
> > the capacitor) and STILL got that infernal hum! 
> > 
> > Considering I will be using this with teletype gear (28's) and from 
> > what I understand voltage regulation is not that critical, couldnt 
> > I merely substitute the transformer for any garden variety one? 
> > (hopefully one that doesnt hum!) Like, perhaps, the kind in an ST6 
> > or similar? Or course, locating such a beast might not be trivial. 
> > 
> > Thanks again, I will do more studying tonight 
> > Eugene 
> > 
> > 
> > -----Original Message----- 
> > From: KC0NNC at aol.com [mailto:KC0NNC at aol.com] 
> > Sent: Sunday, October 9, 2005 09:37 PM 
> > To: ehertz at tcaf.org, WA5CAB at cs.com, greenkeys at mailman.qth.net 
> > Subject: Re: [GreenKeys] 120VDC power supply noise? 
> > 
> > If you have a variac, try placing the supply on the variac, and see 
> > how stable the output voltage is as you run the ac input voltage up 
> > and down, If this is a sola unit, then you should see a very small 
> > change in the DC output as you run the ac mains from 100 to 140 vac 
> > input. 
> > 
> > also, you could place a 1 ohm resistor in the two transformer 
> > output leads before the ac capacitor and the bridge rectifier, and 
> > all the components that follows, and then place the ac dvm, across 
> > each resistor, and see what the voltage drop is across each 
> > resistor, this will tell you if the following circuitry is pulling 
> > excessive current, and what type of current. I would also try and 
> > estimate the supply output voltage and current capability. 
> > 
> > 
> > Lets say it is rated at 110 vdc out at 1 amp. Then you could use a 
> > 100 watt incandescent light bulb for a load, and see how the supply 
> > behaves, while running the variac up and down. also try smaller 
> > bulbs to see how it regulates under less loading. etc, etc. I would 
> > consider leaving some kind of resistance into the bridge for surge 
> > protection. 1 to 10 ohms carbon 2 watt generally works well, 
> > depends on the required output current of the supply 
> > 
> > sort of fun qualifying power supplies in this fashion. I once had a 
> > 4 kV @ 1 amp. DC supply for an Eimac tube I needed to check out, 
> > and series the appropriate number of 1 amp. 120 vac bulbs (about 40 
> > of them)[cheap enough at $0.25 ea.} set them on a plywood board, 
> > and ran it for an hour or so... confirming the supply was ok, then 
> > went on to find the bad tube socket under the 4cx3000 Eimac tube. 
> > 
> > At 60 years of age, I can attest that I was, and continue to be, 
> > quite careful while working with these voltages and currents. 
> > 
> > 73's 
> > Harvey E. Smith, KC0NNC 
> > 2020 Baculite Mesa Road 
> > Pueblo, CO., 81001-2456 
> > 
> > 719 406 9735, 719 671 2671, 719 546 1418 
> > 
> > zzzz/ryry 
> > 
> > 
> > 
> > _______________________________________________ 
> > GreenKeys mailing list 
> > GreenKeys at mailman.qth.net 
> > http://mailman.qth.net/mailman/listinfo/greenkeys 
> > 
> > 
> 
> 
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