UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - AVO CT160

MikeViking · 15th Feb 2018, 11:24 am

Hi. My name is Mike. First time poster.

I picked up an AVO ct160 recently. Case is a little sorry and the panels need a clean but the electronics and internals all look clean. I cannot see any modifications or burnt out components. The 8uF filter cap isn't bulging or leaky. Yet to test that. Fuses were good when it arrived.

I meant to put it on my variac to start it up first time but forgot to turn down the voltage. So I accidentally dropped 240vac onto it. Oops.

Nothing went bang. No smoke. The red power lamp came on. But the relay activates immediately. Only a split second buzz of the really then it activates. Panel meter lights up red.

I have the rotating dials all set to zero. I rolled the pots and switches down to the lowest volts or amp settings. The test is in the SET mode as per the procedure to verify the mains. The needle never moves before the protection relay kicks in.

Open to suggestions. It would appear I have a short somewhere in the screen or anode volts (switch perhaps?) drawing too much current thereby activating the relay. Could be the SET Ia switch as well that's tied to the relay and V1b and the 50v tap.

Or perhaps the diode valve in V1a has an issue. I was going to pull the 2 valves and then power on but it looks like the relay relies on current through the diode to activate.

Thoughts??

15th Feb 2018, 11:24 am	#1
MikeViking Triode Join Date: Feb 2018 Location: Brisbane, Queensland, Australia Posts: 17	AVO CT160 - relay activates at power on Hi. My name is Mike. First time poster. I picked up an AVO ct160 recently. Case is a little sorry and the panels need a clean but the electronics and internals all look clean. I cannot see any modifications or burnt out components. The 8uF filter cap isn't bulging or leaky. Yet to test that. Fuses were good when it arrived. I meant to put it on my variac to start it up first time but forgot to turn down the voltage. So I accidentally dropped 240vac onto it. Oops. Nothing went bang. No smoke. The red power lamp came on. But the relay activates immediately. Only a split second buzz of the really then it activates. Panel meter lights up red. I have the rotating dials all set to zero. I rolled the pots and switches down to the lowest volts or amp settings. The test is in the SET mode as per the procedure to verify the mains. The needle never moves before the protection relay kicks in. Open to suggestions. It would appear I have a short somewhere in the screen or anode volts (switch perhaps?) drawing too much current thereby activating the relay. Could be the SET Ia switch as well that's tied to the relay and V1b and the 50v tap. Or perhaps the diode valve in V1a has an issue. I was going to pull the 2 valves and then power on but it looks like the relay relies on current through the diode to activate. Thoughts??