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Old 8th October 2010, 11:16 AM   #1
M Gregg is offline M Gregg  United Kingdom
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Default Aikido tube connections.

Hi,

I have three questions for those that may have built the Aikido line stage.

On the Aikido line stage drawing it shows connections for input 2 "tube 1" and pin 7 input "tube 2." Both halves of the line stage are using ECC88 so why are the tube triodes inverted for the other channel? Can we not use pin 2 input for each side ?

Also pin 9 screen shown linked to ground with a 0.01 cap, why is this not straight to earth?

Heaters, has anyone found if the voltage divider method or just floating with the 0.1 cap to ground is the preferred method?

Thank's for any input!

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M. Gregg
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Old 8th October 2010, 12:17 PM   #2
M Gregg is offline M Gregg  United Kingdom
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Here is the link to the schematic!

Aikido Cathode Follower & More Triadtron

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M. Gregg
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Old 8th October 2010, 12:55 PM   #3
M Gregg is offline M Gregg  United Kingdom
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O.K.

So I find pin 9 is the screen on 88 and heater center tap on 82/83 etc. That makes sense, so it is to allow for different tube types!

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M. Gregg
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Old 8th October 2010, 01:08 PM   #4
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It looks like the PC board is designed with channel 2 as a mirror image of channel 1.
Reversing the tube sections on one channel would make it simpler to design a "neat" circuitboard layout. Since both sections of the tube are electrically identical, the performance should be pretty much the same in both channels.
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Old 8th October 2010, 01:42 PM   #5
M Gregg is offline M Gregg  United Kingdom
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Frank Berry,

thank's for your input. I could not see any reason for the reversal except as you say layout.

Here is another thought,

If I was to run the heaters in series IE 12V and put the HT with divider in the middle of the two this should give me a balanced lift for the two tubes.

Any thoughts

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M. Gegg
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Old 8th October 2010, 03:39 PM   #6
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Broskie's designs usually have a provision on board the PCB for 12 v series heaters in the form of jumpers. He then asks you to lift the power supply by 1/4 B+ with a voltage divider and I think a location for those resistors is found on the PS board.
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Old 8th October 2010, 03:39 PM   #7
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Hello,
This is the story for the 9 pin as I recall it.
The pinout for the tubes that will work in the JB PCB or circuit is the same except for the 9 pin. Sometimes it is the center of the heater and sometimes it is an isolation screen or fence between the triodes in the envelope. Tie the screen or fence directly to ground is ok. Tie the heater directly to ground it is a short circuit. Use the 0.1 uf capacitor for the heater it acts as a bypass, for the isolation screen or fence it is a AC ground.
DT
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