LEAK Troughline EM87/EM84 - UK Vintage Radio Repair and Restoration Discussion Forum

percival007 · 2nd Aug 2020, 12:22 pm

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.

ms660 · 2nd Aug 2020, 12:51 pm

Is the cathode grounded properly?

Lawrence.

percival007 · 2nd Aug 2020, 1:02 pm

Quote:

Originally Posted by ms660

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.

percival007 · 2nd Aug 2020, 1:59 pm

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.

ms660 · 2nd Aug 2020, 2:06 pm

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

Lawrence.

dazzlevision · 2nd Aug 2020, 2:08 pm

Quote:

Originally Posted by ms660

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.

ms660 · 2nd Aug 2020, 2:15 pm

Quote:

Originally Posted by dazzlevision

Quote:

Originally Posted by ms660

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.

2nd Aug 2020, 12:22 pm	#1
percival007 Heptode Join Date: May 2005 Location: Oxfordshire, UK. Posts: 852	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. Attached Thumbnails

2nd Aug 2020, 12:51 pm	#2
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: LEAK Troughline EM87/EM84 Is the cathode grounded properly? Lawrence.

2nd Aug 2020, 1:59 pm	#4
percival007 Heptode Join Date: May 2005 Location: Oxfordshire, UK. Posts: 852	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. Attached Thumbnails

2nd Aug 2020, 2:06 pm	#5
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: LEAK Troughline EM87/EM84 It's a common problem with that type of valve socket. Lawrence.