[Collins] 32V2 relay issues MORE

[Dr. Gerald N. Johnson]

On Tue, 2009-06-09 at 11:39 -0500, wf2u at ws19ops.com wrote:
> Folks,
> 
> I have a weird problem with my "newly reactivated" 32V2 transmitter.
> I acquired the 32V2 about 10 years ago, and only last week I took it  
> down from the "projects" shelf, to clean it and bring it back to  
> operational status.
> After cleaning the layers of dust off the chassis, tubes, etc., and  
> applying contact cleaner on the bandswitch and other switches, I did  
> the almost obligatory conversion to solid-state rectifiers while  
> disconnecting the HV paths from the transformer filament windings. All  
> voltages are normal, the transmitter works perfectly - except... The  
> relay is not pulling in all the way, no matter how I adjust it. A  
> little motion is evident, but it doesn't pull in all the way. The  
> voltage on it is within the ballpark (around 50 V, the coil is a 48  
> VDC coil according to the specs, and measures 2 Kohm)the coil is not  
> hot. If I bring the armature too close to the coil core, the NC  
> contacts open, so this is not an option. If I hold the armature  
> closed, the transmitter works fine as the HV kicks in. Sometimes, but  
> rarely, the relay stays closed after the manual help. There is no  
> mechanical binding (although the contacts springiness feels stiff, but  
> I can't compare it with a working unit), I even put a dab of lubricant  
> on the hinge/shaft of the armature.
> The problem somewhat stumps me, because nothing seems to be wrong...
> I used the transmitter on the air last weekend, with great reports,  
> but it's a two-hand operation, having to use the push-to-talk switch  
> and with the other hand push the relay with a long insulated  
> screwdriver.
> Anyone had similar experience? Possible cure short of trying to find a  
> new relay?
> 
> Thanks in advance for any ideas.
> 
> 73, Meir WF2U
> Landrum, SC
 
Check the resistance of R309 and R310. you will have to unhook one wire
from R310 to measure these correctly. Then check the relay coil
resistance which won't require any wire disconnected. I figure the relay
coil resistance should be about 3000 ohms to get 48 volts with R309 and
R310 of 5000 and 7500 ohms with 240 volts from the low voltage supply.
The voltage from the relay to ground with the PTT circuit open will be
96 volts.

Be sure your PTT switching from the microphone has a good ground. This
transmitter depends on the grounding of the connector shell for the PTT
(and audio) ground.
-- 
73, Jerry, K0CQ, Technical Advisor to the CRA
All content copyright Dr. Gerald N. Johnson, electrical engineer