[Collins] 516f-2 relay mod

[Bob Kemp]

I used to put in that relay mod in power supplies, then I just went back to 
stock and plugged the p/s into a power strip and I use that to switch the 
rig on (leave switch on the KWM-2  on of course) and whatever else I want to 
come on with my vintage station. I have a wall wart connected to a small 
computer fan to cool the rig that comes on at the same time. Power strips 
are a dime a dozen. vs messing with a rewire of the 516F-2.
Bob
wa0vrc
----- Original Message ----- 
From: "Robert Jefferis" <jefferis at antelecom.net>
To: <geraldj at weather.net>
Cc: <collins at mailman.qth.net>
Sent: Monday, August 24, 2009 6:53 PM
Subject: Re: [Collins] 516f-2 relay mod


> IMO, Jerry hit the nail on the head when he wrote "the slightly
> delicate switch in the radio". The switch contacts are not the main
> problem. They will withstand the power transformer primary switching
> transients fairly well. The real problem with the switch is
> mechanical. The switch cam is fastened to the switch body with a
> swaged mechanical connection to a piece of circuit board material
> through a long, thin cylindrical shaft. With use, this tends to get
> wobbly and causes switch failure symptoms that seem to be erroneously
> attributed to arcing problems. You can actually fix the mechanical
> defect if you have good hands and some good epoxy or good swaging tools.
>
> The relay mod is useful and trivial. Just trace the wiring and use a
> 515F-2 schematic to sort out the change that was made, whichever
> variant it might be.
>
> Bob, KF6BC
>
> On Aug 24, 2009, at 11:16 AM, Dr. Gerald N. Johnson wrote:
>
>> On Mon, 2009-08-24 at 14:37 +0000, cpa599 at gmail.com wrote:
>>> Where can I find documentation for this mod?
>>> I have a 516F-2 which has recently given me a problem ( no power
>>> out).
>>> It has the the relay but no schematic or other documentation.
>>>
>>> Any help would be appreciated.
>>>
>>> Terry
>>> W8EJO
>>> ______________________________________________________________
>> As far as I can find, the relay mod came from Bud Whitney. It
>> shouldn't
>> be a complex change to the 516F-2 schematic. In the original schematic
>> there is a pair of wires that go to the radio that are switched. To
>> add
>> a relay that transformer primary would go to the relay contacts and
>> that
>> switched pair of wires would supply power to the relay coil. It
>> reduces
>> the current to the slightly delicate switch in the radio. When I built
>> my own supply I chose to not use the switch in the radio for primary
>> power, but put the power switch on the power supply.
>>
>> The power supply problem could still the the switch contacts in the
>> radio, or the transformer, or the primary fuse, or the added relay.
>> -- 
>> 73, Jerry, K0CQ, Technical Advisor to the CRA
>> All content copyright Dr. Gerald N. Johnson, electrical engineer
>>
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