could be a bad capacitor, did you clean the relay? i dont know if there is a vibrator tube in these radio or not,,,but if it has one could be that too,,,,
First you need to make sure that the tone alert jumper plug is plugged in because this brings audio signals to the modulator from other circuits inside the unit. if this is missing or not wired right, not connecting right, etc this can give you problems as it completes the audio and squelch circuits for this unit. There appears to be some capacitors on the plug as well (I dont have or own a M2). Then you need to crack that plastic housing open if you cant get it apart and clean the relay. You might have to break it apart or use a pair of sharp wire cutters and work at it getting the plastic off until you can get to the contacts. This whole M2 unit is controlled through the relay so this is a vital area and dirty contacts could give you the problem(s) your having, I have seen it before. Just because its making clicking noises doesn't mean its working (contacting) properly when it most likely has oxidation on the contacts and they are probably black! (like EVERY radio I have worked on that is from the 60's or 70's). Also, spray the tube pins and sockets as well inside with electronics cleaner. The tubes to check are V10 (12AU7), V5 (6AW8), and V6 (12AB5). These are the tubes for the volume and audio circuit/modulator and could in relations to this issue. If the tubes are replaced with known good ones, then you have many other variables at hand, such as inter-stage coupling capacitors, series audio resistors or other possible issues from the power supply as others have pointed out. Have you checked that it is putting out any power and is on frequency? This should be easy to fix as I know this radio quite well from the schematics and have the service manual. Since the radio is roughly 48-50 years old, there are many potential variables with troubleshooting issues at this age now.
First you need to make sure that the tone alert jumper plug is plugged in because this brings audio signals to the modulator from other circuits inside the unit. if this is missing or not wired right, not connecting right, etc this can give you problems as it completes the audio and squelch circuits for this unit. There appears to be some capacitors on the plug as well (I dont have or own a M2). Then you need to crack that plastic housing open if you cant get it apart and clean the relay. You might have to break it apart or use a pair of sharp wire cutters and work at it getting the plastic off until you can get to the contacts. This whole M2 unit is controlled through the relay so this is a vital area and dirty contacts could give you the problem(s) your having, I have seen it before. Just because its making clicking noises doesn't mean its working (contacting) properly when it most likely has oxidation on the contacts and they are probably black! (like EVERY radio I have worked on that is from the 60's or 70's). Also, spray the tube pins and sockets as well inside with electronics cleaner. The tubes to check are V10 (12AU7), V5 (6AW8), and V6 (12AB5). These are the tubes for the volume and audio circuit/modulator and could in relations to this issue. If the tubes are replaced with known good ones, then you have many other variables at hand, such as inter-stage coupling capacitors, series audio resistors or other possible issues from the power supply as others have pointed out. Have you checked that it is putting out any power and is on frequency? This should be easy to fix as I know this radio quite well from the schematics and have the service manual. Since the radio is roughly 48-50 years old, there are many potential variables with troubleshooting issues at this age now.
I sprayed the relay contacts with cleaner and checked a bunch of stuff.....checked all the tubes.....V9 is between good/bad....V1 and V2 both weak...didnt see any burned or damaged caps or resistors.....made a tube chart......tracing wiring until my head hurt....ha ha
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Couple sources for what your looking for;
K5SVC : Tube Guy...top self / good man to deal with...
Gary
Thanks guys...I appreciate the help.![]()
Are u guys talking about that huge paper cap next to the transformer?
The can is the vibrator
The cap can I was referring to is in the browning and trams, it is 3 caps in those units and not worth the expense when you can get 3 separate caps for much cheaper.
Yes the large paper cap, it should be 80uf/450vdc, replace that with a new 100uf/450vdc.
I have a 80uf 450v on hand...ok to use that ?