[Collins] problem with 516-f2

Fri May 27 22:30:21 EDT 2011

The no load voltage with tubes would a bit lower because of the greater 
forward drop with tubes, but if the bleeder resistors aren't connected, 
the voltages will be high. There's about 800 volts RMS on the high 
voltage rectifier plates, with no load that's going to rise depending on 
the bleeder resistors to nearly 1.414 times 800 or 1130 volts and the 
275 low voltage could rise to 389 volts. Though you may have one of the 
transformers with more AC on the low voltage tap. Some came high and 
were not the best to use on the rig because the higher screen voltage 
makes the PA touchy. Besides circuit tracing, you can check all three 
power resistors for heating. They should warm up considerably with no 
other load on the supply.

The voltage chart in the 32 at -1 manual shows 290 volts on the PA screens 
which are directly connected to the LV power supply when transmitting. 
And 275 volts on a couple low level tube places fed through small RF chokes.

5.5 volts is low for the heater circuit, though many meters have poor 
accuracy on AC. What is your meter?

The power supply was designed for 115 volts line and yours is likely 125 
volts which tends to make the transformer hum from driving the core 
harder into saturation and makes the voltages high. A 10 or 12 volt 
bucking transformer on the line is handy for reducing the line voltage. 
A variac works but visitors tend to turn knobs.

73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association

On 5/27/2011 2:50 PM, yash at aol.com wrote:
>
>        Bought a used supply and did a dumb thing,never powered it up and tested it. Instead I just went ahead and replaced all the caps, the 3-25k wire wounds,put a new line cord  and a new diode for the bias supply.The tubes were smashed and haden't got the two tubes I ordered ,so I put the 2 solid state  tubes I had ,in place. fired up the supply,...no smoke,  but have way too high voltages
>      1.  the bias seems ok,within range when you adjust the pot.
>      2.  the Hi voltage is around 1080 vdc no load.
>      3. the low voltage is around 410  vdc  no load
>      4. the fil reads about 5.5 vac.... seem low?
> there is a low level buzzing noise ,hard to tell, where from, when powered up.
>       I have traced the wiring as best as I can follow it,lots of fadeing on wire colors. Re checked all the new parts for proper direction + -, Iam beginning to get fuzzy eyes. Since there is no voltage  or data chart in the manual ,Iam lost.
>
> Any chance the SS tube replacements causing a problem,that might go away when the tubes are put back, they couldn't cause such a high voltages at no load? Plan to keep the supply on tubes when its finished.
> would be grateful for any help on this.
> thanks
> dale wt4t
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