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Source for ECL86 tubes?

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slimecity

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Joined 2009
#1
Hi there - I have a NZ built amplifier based on a Mullard 10-10 design. Its here -

Fountain Gemsonic - Solid State, Valve & Tube Hi-Fi

I realise that prices of tubes have sort of skyrocketed since I last tinkered with tubes. I have tried contacting these guys but havent heard back - their prices arent too bad: Vacuum Tubes - Audio Tubes - ESRC Vacuum Tubes - Electron Tubes

I have found a supplier on epay who says he can match them. Given the scarcity of these tubes now I feel I may need to buy off him - he has good feedback: ECL86 vari e STRK MEBIDX IT trksid p2055119 m1438 l2649 | eBay

OK so the epay source I cited above said he can supply four tubes - however they are from different manufacturers.

I asked him if he will match for current draw at tube amp voltages. He replied that they are tested at the makers datasheet settings.

Is this good enough?

Perhaps if I drop new pairs in and first listen for hum (to indicate one is drawing less/more current than the other), and then test the current draw of each tube - this could be OK?

Cheers
 
#3
PCL86 are pretty abundant even down here - throw a 12vac transformer in to run the heaters and you can get an endless supply of PCL valves to run it for the rest of your life.

I have a 10-10 in the workshop for a rebuild and this is the path I'll probably go.
 
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#4
aardvarkash10 said:
PCL86 are pretty abundant even down here - throw a 12vac transformer in to run the heaters and you can get an endless supply of PCL valves to run it for the rest of your life.
Click to expand...

Agreed. Depending on how many O/P tube RC bias networks are present, either matched pairs or a matched quartet of bottles will be required.

The "6" V. winding in situ could be used to feed a DC heater supply for the EF86s. That would have a positive impact on the hum level.

As the OEM parts have long since literally dried out, it is a matter of routine to replace all electrolytic caps., in units of this "vintage".

It seems the unit employs SS B+ rectification. Replacing the old, noisy, diodes with quieter parts, like the UF4007 is a worthwhile, low cost, tweak.
 
#5
I wouldnt mind trying this with replacement ECL86's first if I can. I am a noob with tube circuits and dont feel confident enough to make the PCL86 mod - I also heard that different manufacturers might require different heater voltages to run the PCL's. So, hmmmmm, maybe I will think about this....

I have a pair of telefunkens in there at the moment - there is a hum in one channel that follows 2 of these tubes, when I swap them to the other side.

The original resistors have been replaced by a prior owner. I finished recapping the electos' today with Pansonic FC's. There is a crappy little red bridge rectifier in there currently that I was also thinking could be upgraded.

So would I be OK to purchase a matched quad/2 matched pairs from the ebay seller - based on his decription of matching method?

thanks
 
#7
I am a noob with tube circuits and dont feel confident enough to make the PCL86 mod - I also heard that different manufacturers might require different heater voltages to run the PCL's.
Click to expand...

Tubes are high voltage/low current depletion mode devices. You work with them much in the way you work with a DN2540.

All Pxn tube types, including the PCL86, are intended for use in 300 mA. series heater strings. Build a "500" mA. capable DC supply of "30" V. and current regulate it to 300 mA. using a LM317. More than 1 post is available off the WWW showing how to set a LM317 up as a current regulator. "Float" the current regulated rail and connect the PCL86 heaters, wired in series, to it. Connect the junction of the UCL86 heaters to ground via a cap., for hum/noise control.

So would I be OK to purchase a matched quad/2 matched pairs from the ebay seller - based on his decription of matching method?
Click to expand...

Negative! Proper matching of tubes requires specimens from the same plant and (preferably) the same production run, as a starting point. Then, careful measurements of transconductance (gm) and cathode current, under real world conditions, are made. Specimens whose measurements are quite close constitute a pair ...
 
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#9
Eli Duttman said:
Tubes are high voltage/low current depletion mode devices. You work with them much in the way you work with a DN2540.

All Pxn tube types, including the PCL86, are intended for use in 300 mA. series heater strings. Build a "500" mA. capable DC supply of "30" V. and current regulate it to 300 mA. using a LM317. More than 1 post is available off the WWW showing how to set a LM317 up as a current regulator. "Float" the current regulated rail and connect the PCL86 heaters, wired in series, to it. Connect the junction of the UCL86 heaters to ground via a cap., for hum/noise control.



Negative! Proper matching of tubes requires specimens from the same plant and (preferably) the same production run, as a starting point. Then, careful measurements of transconductance (gm) and cathode current, under real world conditions, are made. Specimens whose measurements are quite close constitute a pair ...
Click to expand...

Thanks Eli - if I cant get the right price for ECL's - then I will make this conversion.....
 
#10
the circuit diagram
 

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