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Help with Grunow Model: 660 Chassis:6C [message #25886]

Wed, 20 September 2006 17:44

Bruce Arrowood
Messages: 2
Registered: May 2009

Esquire

I found a very nice Tombstone Grunow Radio and I have it playing. I don't have a schematic and there is a problem in the volume control circuit. It plays loud on low volume and goes lower when turned up? I have checked all the componets in the immediate circuit and all are okey. I'm at the point where I need a schematic. I do have some gronow schamatics but they will not match the circuitry. It seems I should not have trouble with this circuit but? Thanks for any consideration.
Brissco

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Re: Help with Grunow Model: 660 Chassis:6C [message #25887 is a reply to message #25886]

Thu, 21 September 2006 09:05

Wayne Parham
Messages: 18786
Registered: January 2001

Illuminati (33rd Degree)

Have you checked to make sure the potentiometer is connected properly? If wires to pins 1 and 3 are reversed, the volume knob works backwards like that.

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Re: Help with Grunow Model: 660 Chassis:6C [message #25888 is a reply to message #25887]

Thu, 21 September 2006 15:28

Bruce Arrowood
Messages: 2
Registered: May 2009

Esquire

Hi. Good idea , I rewired reverse but now there is no control for volume at all, just high volume. The pot. is 1 meg very smooth in operation,and resistance. One side connected with shielded wire to grid of #75 det. tube. The middle connected direct w/ shielded wire to 6D6 IF output transformer, the 3rd end is connected to a cap to ground, ( which I replaced),and a 130K resister to a resister strip measuring 30 ohm to gnd. The tap of the pot. is connected to a cap. to ground which I replaced, also the tap shows good conductance to the middle connection on other side of pot.

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Re: Help with Grunow Model: 660 Chassis:6C [message #25889 is a reply to message #25888]

Thu, 21 September 2006 19:17

Wayne Parham
Messages: 18786
Registered: January 2001

Illuminati (33rd Degree)

One side of the potentiometer should probably be connected to ground, the other to a driver stage output and the wiper to the input of an amplifier stage.

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