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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 10th Jun 2021, 7:40 pm   #1
John_BS
Octode
 
Join Date: Dec 2008
Location: Wincanton, Somerset, UK.
Posts: 1,322
Default Fault in ECL86

I've been revisiting a Dynatron record player which I'd previously "restored" circuit-wise. The original Mullard ECL86's tested 100%, but having changed the cartridge for a more appropriate type, I was greeted with truly epic distortion.

Big sigh and everything out of the case again: the phase-splitter triode should have 30 odd volts on its cathode, but it was up at 100V and only a few volts below the anode. Not having found any component problems, I removed the valve and tried it on the AVO. It said there was an issue with insulation "anode to rest". When I removed it and gave it a firm tap with a screwdriver, all came good. Back in the record player and the biasing is now correct. Is it safe to leave this as it would be a shame to replace one of two original valves with 100% emission.

John
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Old 10th Jun 2021, 8:06 pm   #2
Ed_Dinning
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Join Date: Jan 2004
Location: Newcastle upon Tyne, Tyne & Wear, UK.
Posts: 6,791
Default Re: Fault in ECL86

Hi John, it may or may not have a lot of life in it yet.
Analyse the circuit and see if the fault re-appears it will cause expensive damage. If not a note to self within the machine as to what the problem was

Others may disagree

Ed
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Old 10th Jun 2021, 9:09 pm   #3
John_BS
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Default Re: Fault in ECL86

Ed: no, it's got 100K to both anode & cathode, so only passes 1mA !

John
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Old 10th Jun 2021, 11:25 pm   #4
kalee20
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Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 5,747
Default Re: Fault in ECL86

It's probably some debris, unfortunately rattling around in the valve.

If it works, leave well alone - it may carry on fine, but die if you pick up the equipment and turn it on its side.

As nothing is going to get damaged, according to your checks, you might as well carry on and enjoy its service.
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Old 11th Jun 2021, 9:27 am   #5
John_BS
Octode
 
Join Date: Dec 2008
Location: Wincanton, Somerset, UK.
Posts: 1,322
Default Re: Fault in ECL86

It's back in and working, so fingers crossed!

Thanks for the advice.
John
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