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

[Garey Barrell]

Jerry -

According to the manual I have, the original looks to be a 5% part. so they 'really' wanted 
24k!  :-)   Especially since R4 and R5 were 25k and from the part number look to be simple 
standard part numbers.  It takes some 'juice' to get the bean counters to add a 'new' part.  
"Why cantcha' just use the same part as the other two".   Heard it before...  :-)

I'm sure that would have been a custom part at that time.  24k would be more likely to be a 
standard now, but when this design was done 25k would have been more likely....

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>

Dr. Gerald N. Johnson wrote:
> 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