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Old 2nd Aug 2020, 12:22 pm   #1
percival007
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Default LEAK Troughline EM87/EM84

Hi All,

I am very close to finishing my refurbishment of a LEAK Troughline II I've had on my to do list for some time.

I have taken several Pictures (including one where I have labelled all of the Resistors, their positions and Value) and can post them if it would help anyone else.

Anyway, my question, now I've got the thing up and running and sounding wonderful, I cannot get the EM87 to work properly.

The Circuit says it should be an EM84 ( I have two of these also) but fitted to mine was an EM87.
When I switch the AFC OFF I only get a very weak glow from the Display and I cannot see any Bars closing or opening when on-tune and off-tune.

It is getting 6.3V AC Heater Volts.
I am getting on the Grid around 0V DC when off-tune which goes to -12V DC when on Tune.
I have 158V DC on Pin 6 however, where the circuit says 20V DC (I think, though it could be 30V, it's not very clear) on Pins 7 & 9, I have 148V DC.
It is the same with the EM84's.

R24 measured 1M before my work but there is a good 680K fitted now.

Any help would be appreciated as I can't think what's going on other than I have three failed Valves (?).

I have attached the circuit for my unit which is slightly different to the ones more readily available on-line but the EM87/4 part is identical.

Many thanks,

James.
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Old 2nd Aug 2020, 12:51 pm   #2
ms660
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Default Re: LEAK Troughline EM87/EM84

Is the cathode grounded properly?

Lawrence.
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Old 2nd Aug 2020, 1:02 pm   #3
percival007
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Default Re: LEAK Troughline EM87/EM84

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Originally Posted by ms660 View Post
Is the cathode grounded properly?

Lawrence.
Well, I thought it was. Pins 3 & 4 are both connected with a wire Link to the Chassis.
But now you've mentioned this, I am begining to doubt the Valve Base. Without the Clip, holding the Valve in place, it is a little loose fitting so maybe the Cathode isn't actually being Grounded (?).

I will check and report back.

Many thanks,

James.
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Old 2nd Aug 2020, 1:59 pm   #4
percival007
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Default Re: LEAK Troughline EM87/EM84

Lawrence you're a Gent.

I'm one of those folk who has to know why even when you've sorted the problem so please see the attached photo.
Pin 3 of the Valve base is broken and obviously wasn't making good contact/any contact. So the Cathode wasn't being Grounded as you suspected.
New Valve Base and the EM87 is working fine.
LEAK only recommend it's use during tuning, once the desired Station is found, the AFC should be turned ON which turns OFF the EM87 during listening. But it's good to have everything working.

Many thanks,

James.
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Old 2nd Aug 2020, 2:06 pm   #5
ms660
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Default Re: LEAK Troughline EM87/EM84

It's a common problem with that type of valve socket.

Lawrence.
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Old 2nd Aug 2020, 2:08 pm   #6
dazzlevision
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Default Re: LEAK Troughline EM87/EM84

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Originally Posted by ms660 View Post
It's a common problem with that type of valve socket.

Lawrence.

Made by McMurdo (UK). I salvage unused/unsoldered contacts from scrapped radios, etc. They are easy to remove once the solder tag part is gently straightened up.
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Old 2nd Aug 2020, 2:15 pm   #7
ms660
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Default Re: LEAK Troughline EM87/EM84

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Originally Posted by dazzlevision View Post
Quote:
Originally Posted by ms660 View Post
It's a common problem with that type of valve socket.

Lawrence.

Made by McMurdo (UK). I salvage unused/unsoldered contacts from scrapped radios, etc. They are easy to remove once the solder tag part is gently straightened up.
I know, used to pack up back in the day, the other crap ones were were the 3 sided contacts that were fitted to some ceramic valve holders, one wing used to fall off if you tried to tighten them up a bit (brass type metal fatigue)

Lawrence.
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