PYE C12 system meter problem

[Michaelr]

Hi ,

I need Help/advice !

I am preparing a PYE c12 transceiver to use on the bands on some AM nets and possibly winter QRP.Not having much spare time lately progress has been slow. The unit is in excellent condition but suffering from storage issues such as oxidised switches etc any way that is for another day to report when I have it fully working.

The current issue is that the main system meter used for monitoring various voltages and currents reads Low by about 30% consistently. It is a 500micramp movement and I have it stripped down at the moment. The movement appears free moving, the question is for any with good experience of meter movements could you advise me of any checks or adjustments that are possible.

Regards
Mike

[Skywave]

:idea: Since the error appears on both the V and I ranges, it makes me wonder if there is a 'swamping' resistor - which may be fitted inside the meter housing itself - that has gone HR.
You also refer to oxidised switch contacts. Since this meter monitors V & I, presumably there is a switch for this: dirty contacts?

Al.

[pwdrive]

Hello Mike, I am not an expert on meters but the first thing I would check if not already done so would be it's FSD with its rated current passing through it or by temp. substitution with say an AVO.
I have a receiver with a similar concept insofar that it's meter can be switched to monitor the anode current of any of the valves in the receiver thus giving a go / no go emission reading test, it is however dependant on AGC/RF gain settings which are Off and Full respectively, as to wether or not a meter movement can loose say 30% sensitivity I am not sure enough to say, I have never had it happen but that is not to say that it can't, defective internal shunt etc.

Lawrence.

[Michaelr]

:idea: Since the error appears on both the V and I ranges, it makes me wonder if there is a 'swamping' resistor - which may be fitted inside the meter housing itself - that has gone HR.
You also refer to oxidised switch contacts. Since this meter monitors V & I, presumably there is a switch for this: dirty contacts?

Al.

Al,

I am referring to the meter which in circuit is always measuring current, there are no swamping resistors, there is a mutiway swtch with appropriate series resistors in place . The external multiway switch I have cleaned and have checked correct reading by removing the faulty meter and substituting my dvm on low current range. The readings on the dvm are exactly as they should be so it is a meter movement problem.I suspect it is either a patially shorted coil or the torsional springs. After dinner I am going to have a good luck under a strong light and magnifying glass.

I do not hold out much hope on this one

Mike

[Michaelr]

Hello Mike, I am not an expert on meters but the first thing I would check if not already done so would be it's FSD with its rated current passing through it or by temp. substitution with say an AVO.
I have a receiver with a similar concept insofar that it's meter can be switched to monitor the anode current of any of the valves in the receiver thus giving a go / no go emission reading test, it is however dependant on AGC/RF gain settings which are Off and Full respectively, as to wether or not a meter movement can loose say 30% sensitivity I am not sure enough to say, I have never had it happen but that is not to say that it can't, defective internal shunt etc.

Lawrence.

Hi lawrence ,

Sorry for the late reply I missed your post (busy day yesterday! ). I have checked the meter and it is consistently reading low on current ( standalone outside of the transceiver ) and I think it is due to one of the reasons I state in my reply to Al.

Last night I checked the movement and there are 2 torsional springs , one at the top pivot point of the meter needle shaft and one at the bottom. This is standard construction. The top torsional spring is not uniform in its coil, one side is "bunched ". The bottom spring is uniform in its coil. I also note that the needle shaft is slightly loose in it's top pivot point .

I will look further into it this morning.

This is one for the Horologists among the group I think.

Mike

[pwdrive]

Hello Mike, I have had limited sucsess with meter springs but they never turn out quite right, I can't really add to what you have said, it must be disapointing, i presume that the C12 is still usable though, lets hope a solution turns up at some point.

Lawrence.