Model 24 won’t power OFF

[elkasdad]

My Model Twenty Four will not power off. Into the back of the preamp’s switched power outlets I have a Model 250 amp plugged into the outlet with the “protector” and an AR “the turntable” plugged into a second of the three “switched” outlets. The amp and the turntable are receiving power and working fine. Both turned on and off as expected with the preamp before it started to no longer turn off today.

I’ve tried unplugging the Model 24 and tried pushing the red protector switch, to no effect.

I’ve tried unplugging the amp from the preamp and this doesn’t affect the problem. Interestingly, the preamp still triggers the delayed power to the amp when I turn the preamp on and off. So the preamp doesn’t turn off when I depress the power button, but when I push the power button in again (turn the preamp power on), after a second or two, you can hear the preamp send power to the amp, via the switched and protected power outlet.

I don’t know much and I know folks here do, so any help much appreciated.

 

[tonebells]

The 24 has a mute relay that shorts the outputs to ground when it is switched off. It is delayed when turning on. As you can see the relay is controlled by a second switch. So the mute can work even if the power switch has a problem. If the unit is not powering off either the power switch is bad or the snubber cap C011 is shorted. The circuit breaker does not protect the outlets.

Tony

 

[elkasdad]

The 24 has a mute relay that shorts the outputs to ground when it is switched off. It is delayed when turning on. As you can see the relay is controlled by a second switch. So the mute can work even if the power switch has a problem. If the unit is not powering off either the power switch is bad or the snubber cap C011 is shorted. The circuit breaker does not protect the outlets.

Thank you!

 

[elkasdad]

OK Ive opened it up and it seems replacing that power switch is not a task for a rookie.

 

[tonebells]

The yellow and red wire nearest the face are for the relay. The wires furthest from the face are the power. Do you have a volt meter to test with? I have one of these open I will look to see where the snubber cap is.

Tony

Tony

 

[elkasdad]

Lo and behold, now that I have it on the operating table, the power switch has started working again. Does that wave any flags for the pros in the room? Also this switch doesn't appear to have a snubber cap. Would that go across the one of the two sets of "unused" terminals on my switch?

 

[elkasdad]

The yellow and red wire nearest the face are for the relay. The wires furthest from the face are the power. Do you have a volt meter to test with? I have one of these open I will look to see where the snubber cap is.

Thank you - And I do have a meter

 

[tonebells]

With the switch off and no power there is about 35 ohms across mine.

Tony

 

[tonebells]

The switch looks untouched.

Tony

 

[elkasdad]

With the switch off and no power there is about 35 ohms across mine.

OK thank you. I will test this tomorrow. So thats the snubber? Ive got what looks like the exact same one.

 

[tonebells]

That's it. If you trace the wires you will see that it is connected to both sides of the switch.

Tony

 

[Don Lubin]

I've got a Model 24 that I have used with two 250 power amps. The switched outlets on the 24 were not designed to handle anything close to the current requiements of a 250. My unit says 60 watts next to each outlet. What I did was get a large (20A ??) 120V relay and plugged the coil into the Model 24 switched outlet and then wired the relay contacts to connect the 250 to the 120V mains. That way, the power switch on the 24 never sees high currents.