[Collins] {Collins} Question on 516-F2 PS

[Dr. Gerald N. Johnson]

24K is a standard 10% value. Wire wound resistor makers often stuck with 
their pre standard values, like 25K.

The 25K has a tolerance too and could be high or low. 5% would be +/- 
1.25K. 10% would be +/- 2.5K. The true value for best voltage regulation 
(not jumping too high at no load) depends on the filter capacitor value 
and it has a much wider tolerance, sometimes +40 -10 or other wide 
variations.

There is a graph in vintage ARRL handbooks that they may have used. I 
know I showed it to my boss at Collins who had been in charge of the 
group designing the S-line and power supplies.
http://www.geraldj.networkiowa.com/papers/Capfilterps.jpg
It clearly shows the effects of transformer, rectifier and filter 
capacitor on capacitor input filters. The filter choke complicates 
things but eases the every half cycle peak current.

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


On 9/14/2015 3:59 PM, Garey Barrell wrote:
> I don't know that much about the 516F-2, but choke input supplies
> require a minimum load for best regulation.
>
> I suspect that Collins engineers slipped their slide rules and came up
> with 24k as that minimum load.
>
> That said, the original part was +/-5% so 25k is JUST within tolerance! :-)
>
> 73, Garey - K4OAH
> Rome, GA
>
> Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
> and TR-4/C Service Supplement CDs
> <www.k4oah.com>
>
> Stanley M Miln wrote:
>> Hi Guys,
>> Typically with Tube Equiment 20% tolerance is
>> acceptable. Probably with Frequency Components
>> that may not be so, like with the PTO.
>> All the Bleeder Resister does is discharge the Caps
>> after the Supply is shut off. It also may help
>> with Regulation. I can not see the Value being that
>> Critical.
>> Stan K6RMR
>>
>>>
>>> How important is R6 (24K) replaced with a 25K. A 25K resistor with 5%
>>> tolerance is 23.750K so would that be close enough to 24,000 to work?
>>> Comments please. Thanks.
>>>
>>> JAC
>>>
>
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