[Collins] 32V2 relay issues MORE

[Dr. Gerald N. Johnson]

On Wed, 2009-06-10 at 08:49 -0500, wf2u at ws19ops.com wrote:
> Jerry,
> 
> I went through all these steps already... (I used to make my living as  
> an EE before I switched to the IT field...).

Aha.
> 
> The coil resistance is specified in the parts list as 3000 ohm.  

The manual I downloaded didn't specify resistance.

> 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

That's how I came up with 3000 ohms for the coil.

> 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...

And wire wound resistors usually don't change value much. A circuit mod
that could drive that relay harder would be to connect a capacitor,
probably a microfarad or a few from the junction of R309 and R310 to
ground. It would slap the relay closed, then hold it with 50 volts,
though you've found it didn't hold when pushed in manually all the time.
Which tends to say that voltage can't be holding at 50 volts, though
that doesn't match your measurements. Is there a bad solder connection
in the circuit? Collins adherence to the solid mechanical connection,
solder later can lead to solder not always penetrating the wad of wires
to make a connection as permanent as Collins expected. Maybe just heat
applied to all the connections will have an effect.
> 
> 73, Meir WF2U
> Landrum, SC
> 
If it works well with the 50 volt regulated supply, it can't be a
mechanical problem though a gummy shaft is suspect at this age.
-- 
73, Jerry, K0CQ, Technical Advisor to the CRA
All content copyright Dr. Gerald N. Johnson, electrical engineer