[GreenKeys] 120VDC power supply noise?

[Don Robert House]

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
>
>