EF86 Woes

Maxwell_E · 7227

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Offline Maxwell_E

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on: January 27, 2013, 05:51:38 PM
I've just finished final voltage checks on my Tode and everything is in great shape. Except the EF86 filaments wont come on. I double-checked the resistances all around, plugged it back in and powered on, still nothing. I thought maybe it was a dark tube, or the screen does a great job of hiding it but I'm not getting anything. I went ahead and did the Voltages checks and it came out great all around and I know the tube is getting a solid 6.1 because the EL84 is lighting up no problem. All solder joints are good and I just wanna make some noise. Is there anything obvious that I'm missing?

Max Tomlinson
SEX amp, Tode guitar amp


Offline Paul Birkeland

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Reply #1 on: January 27, 2013, 05:55:04 PM
If all the voltages are good, the EF86 is lighting.

The EF86's we supply don't offer much (if any) of a glow, but their operation sets the bias for the EL84, so you would really notice if the tube wasn't functioning!

For more light, look for a used mesh plate EF86 on eBay.

-PB

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Maxwell_E

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Reply #2 on: January 27, 2013, 05:58:12 PM
Ok, thank you, I was really worried. I haven't had any experience with EF86's before so I thought I was just missing something simple. I just remembered I gave you guys all my good Tele's, I should have held on to one of them :)

Max Tomlinson
SEX amp, Tode guitar amp


Offline willspeed

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Reply #3 on: January 28, 2013, 05:18:38 AM
I had the same worry - I thought I had a bad tube, since I saw 6.3V at the filament heater wiring, and the tube felt cold. Seems that these EF86s run pretty cool - at least compared to the EL84 which gets hot enough to feel thru the wood case!

Will G.

S.E.X. w/C4S driving SEXy speakers
Seduction w/C4S
Quickie 1.1/ PJCCS
Rega Planar 2 / R200 Tonearm / Ortofon 2M Red / RB250 Tonearm / Ortofon 2M Blue
Tode / Taylor 110 / Taylor 214ce / 94 Tele Tex-Mex Special / Home-hacked Squire Strat / 86 Guild F46NT / Which one next?


Offline Paul Birkeland

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Reply #4 on: January 28, 2013, 07:15:59 AM
Yeah, the EF86 is current starved in this schematic, running several tenths of a milliamp at 20V on the plate and a little more on the screen.  If the tube is left to run for 10-20 minutes, it should be slightly warm, but even the EF86 in the Eros circuit runs fairly cool to the touch.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline willspeed

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Reply #5 on: January 29, 2013, 06:15:29 AM
Just out of curiosity, I know the EF86 is a Winged-C tube, but I couldn't tell what the EL84 was.

Will G.

S.E.X. w/C4S driving SEXy speakers
Seduction w/C4S
Quickie 1.1/ PJCCS
Rega Planar 2 / R200 Tonearm / Ortofon 2M Red / RB250 Tonearm / Ortofon 2M Blue
Tode / Taylor 110 / Taylor 214ce / 94 Tele Tex-Mex Special / Home-hacked Squire Strat / 86 Guild F46NT / Which one next?


Offline Paul Birkeland

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Reply #6 on: January 29, 2013, 07:31:06 AM
The EL84's are Russian Military old stock (for now).

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man