[Collins] 516f-2 relay mod

[Robert Jefferis]

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
>
> ______________________________________________________________
> Collins mailing list
> Home: http://mailman.qth.net/mailman/listinfo/collins
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Collins at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html