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 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

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PostPosted: 23 Dec 2017, 14:51 
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Joined: 09 Oct 2012, 19:43
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Location: Vancouver Canada
If there is ever a need to discharge a capacitor, do so but use a resistor in series with the short. Connect each end of the shorting jumper to the terminals and leave for a few seconds before removing. For these amps 10K at 2-5w would work. A dead short on a cap can cause damage between the conductive fields and the dielectric layer if too many electrons pass from one conductor to the second conductor at one specific area. A hole will form in the dielectric substance causing a short between the conductive layers resulting in a good cap turning bad.


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PostPosted: 23 Dec 2017, 15:39 
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Joined: 04 Jun 2008, 20:59
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Location: Arizona, USA
Hi, Thanks for the addition, Yes correct, I have a cold and was not thinking quite as clearly as normal (some say ...what's new ?:eek: )

Use the resistor, if you make a dedicated thing for this purpose the resistor in the middle of the wire can be insulated with a piece of heat shrink.

Good listening
Bruce

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PostPosted: 23 Dec 2017, 18:39 
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Joined: 13 Jul 2017, 21:24
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Hi Bruce,

What B+ would you expect to see without the tubes plugged in?

Minimum quantity for the boards were three sets. So if you can PM me your address I will send you a set. They seem to check out as faithfully copying your design.
cheers
Beardy


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PostPosted: 23 Dec 2017, 20:09 
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Hi, If you used the same transformer, rectifiers and filters about 280. (1.4 times the RMS voltage of the winding)

Good listening
Bruce

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PostPosted: 23 Dec 2017, 21:23 
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Yes, I use the same transformer and values of resistors and caps. The local supply voltage measures 119+/- and I see 300V with no load
thanks
Beardy


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PostPosted: 24 Dec 2017, 16:26 
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Hi, Allowing for tolerances it is in the right range.

Good listening
Bruce

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PostPosted: 24 Dec 2017, 16:56 
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Hi Bruce,

What would be a good resistor value to use a dummy load instead of the tube. I could then get real numbers without cooking things...
Cheers


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PostPosted: 25 Dec 2017, 16:12 
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Hi, My first question is why do you want to do this? Just finish the build and let the tubes be the load. However...I calculate that a resistor of about 3000 ohms would be needed. I would use a 20 watt one. Be aware it will get quite hot.

Good listening
Bruce

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PostPosted: 25 Dec 2017, 17:53 
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OK I was just trying to avoid burning up the tubes unnecessarily.

So I should see about 150V across the tube when loaded....?

Festive tidings to you and yours,
Beardy.


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PostPosted: 26 Dec 2017, 22:06 
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Hi Bruce,

I measured voltage across Pin 1 & 8
Tube 1 started out at ~280V, after 1 min this dropped to ~178V and after 2 mins ~170V and then after 3 mins to around 167V
Tube 2 started out at 280V, after 1 min, this dropped to ~170V after 2 mins and then after 3 mins to around 168V
seems to be asymptotic and would settle somewhere in the >160V range.
cheers
Beardy


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