[Collins] 32V2 relay issues MORE

[wf2u at ws19ops.com]

Jerry,

I went through all these steps already... (I used to make my living as  
an EE before I switched to the IT field...).

The coil resistance is specified in the parts list as 3000 ohm.  
Everything  is normal. The voltage at the junction of R309 and R310  
measures 110VDC and with the PTT or HV switch on (grounding the other  
side of the coil, it goes to 54V.
A friend with a 32V3 measured these on his, and it's the same within 2 V.
Except for the LV being a tad higher than 240V, all of these  
measurements make sense, and the math gives 48V with 240 VDC into the  
voltage divider, when grounding one end of the coil puts it in  
parallel with the 5000 ohm resistor
Also thinking of bad ground at the switch/PTT, I grounded the low side  
of the coil via a clip lead to the chassis. Same result. - A little  
movement of the armature but it doesn't pull all the way. BTW just to  
eliminate the unlikely possibility of the iron core being permanently  
magnetized in the opposite direction, I switched the wires to the  
coil. Same result.
It's getting weird here: I disconnected the relay from the R309/R310  
junction, and fed it from an adjustable bench supply.
It pulls very positively at 50 V and draws 25 mA, the current is what  
it should be with the 3000 ohm coil.
Back to the workbench tonight and I'll do further measurements on that  
voltage divider. The initial measurements on the resistors agreed with  
the parts list in the manual...

73, Meir WF2U
Landrum, SC




Quoting "Dr. Gerald N. Johnson" <geraldj at storm.weather.net>:

> 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
>
>