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Post subject: Re: Super-Sonic 22 Bias Level
Posted: Mon Jan 14, 2013 10:48 am
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Wow thanks for all the help Bill and shimmilou!
I bought JJ 6V6S tubes from the tube depot as replacements. I was able to check the JJ site and it looks like they are 14w:

http://www.jj-electronic.com/pdf/6V6.pdf

(under "limiting values" - I assume the amp is Pentode configuration)

Thanks for the clarification on what they numbers mean and derive them myself. This has been a major learning experience.


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Post subject: Re: Super-Sonic 22 Bias Level
Posted: Mon Jan 14, 2013 11:26 am
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eriwebnerr wrote:
...(under "limiting values" - I assume the amp is Pentode configuration) ...


Yes, Pentode, meaning all five elements of the tube are used; Plate, suppressor grid, screen grid, control grid, and Cathode. A Tetrode would use four elements; Plate, screen grid, control grid and Cathode. A Triode would use three elements, Plate, control grid, and Cathode. Preamp tubes are dual Triodes, whereas output tubes are typically Pentode or Tetrode. You can usually see this on the schematics.

http://support.fender.com/schematics/guitar_amplifiers/Super-Sonic22_schematic.pdf

This is a 6L6, but the same drawing as a 6V6.
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Post subject: Re: Super-Sonic 22 Bias Level
Posted: Mon Jan 14, 2013 4:06 pm
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eriwebnerr,

Shimmilou said everything I would have said and more. :D

Regarding the Weber bias calculator site, I find the following two calculators to be useful:

Bias Settings For Safe Plate Dissipation - Class AB 70% Class A 90% (Lets you determine the maximum safe plate current for a given plate voltage)

and

Calculate Plate Dissipation Based On Plate Voltage And Cathode Current Readings (As noted, it takes into account screen current and after calculatign things displays the approximate plate current).

The Jim Jones' Bias Table is handy just to see the range of plate current values for a given plate voltage at 50%, 60%, and 70% max plate dissipation (note that as shimmilou said, the 6V6GT shown is only listed as 12 watts while current versions are 14 watts).

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Post subject: Re: Super-Sonic 22 Bias Level
Posted: Mon Jan 14, 2013 4:10 pm
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Thanks all! You have been super helpful - the tubes should arrive Wednesday. I'll let you all know how it turns out!


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Post subject: Re: Super-Sonic 22 Bias Level
Posted: Tue Jan 15, 2013 11:33 am
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iamsomewhere wrote:
Does anyone know what the recommended level is for biasing the new Super-Sonic 22?

Would it be the same as the 65 Deluxe Reverb, since that is what the power section is based off of?


:mrgreen: I just did extensive supersonic 22 work once i am done with my data i shall post but briefly regarding bias. here are some numbers from last night (AND the super sonic 22 has 1ohm cathode resistors in parallel with a diode. on the schematic they are R140 and R-141 on the printed circuit board (i just re-tubed, and swapped out the TL0-72's change a few values)) and improved the ground schema. Now you SHOULD go to the fender support domain and select downloads> schematics>scroll down to almost the bottom of the page and there is the schematic..the resistors are on V6 & 7. Set for 24 mvdc as per their recommendations. (btw compare the Deluxe reverb and super 22's phase inverter circuitry...resistor values are different.

Test equipment is a brand new higher end tektronix lab gear DMM out to 5 right of decimal
so I had;
122 Vac line voltage
with no signal applied my plate voltage was +428.2vdc (measure between 3-8 on V6/7)
With the recommended input signal = 5mvac/zero DC offset Sinusoidal +413vdc

The 6V6 complement are Genelx from the tubestore (i highly recommend the tubestore) :D
so plugging in those numbers into the Weber bias calculator (google it) for 70% dissipation (no signal applied)
6V6 = 19.6mvdc
6V6GTA = 22.8mvdc
Fender states = 24mvdc

From AXE84's calculator
6V6 (Max dissipation 14 watts)
Results: For 428.2 Volts
60% 70% 80% 90% 100% 110%
19.62 ma 22.89 ma 26.16 ma 29.43 ma 32.7 ma 35.96 ma
Recommended Bias point for AB1 operation is 70%

i ended up at 24.6mvdc nice clean 1Khz (audio amplifier standard) with the following readings.

Clipping into an 8.3333 ohm wire wound power resistor was;
Onset = +310Vdc Max volume CLEAN channel and full CW for bass and treble + fat
Max = +330Vdc

So the Doctor says - "pick your own poison"

When i am done with my Vibro king KT-66 conversion i will post a very detailed analysis...and not too deep. :shock: :lol:

same on the 22 once i finish the VK then onto dialing in the stand alone reverb (sozos in it now plus re-tubed 7025, Genalex 6V6 and 6201 (12AT7)

tutorial on biasing + scope stuff
http://web.archive.org/web/200502090108 ... iasing.htm

the archive for the defunct

http://tone-lizard.com/Biasing.htm :mrgreen: 8)

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Post subject: Re: Super-Sonic 22 Bias Level
Posted: Tue Jan 15, 2013 4:36 pm
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The different values of plate resistors on the PIs of the SS 22 and DRRI have only a minor effect on the inverted/noninverted gain values of the two PIs. They have no effect on biasing the power tubes.

The plate voltage does not remain the same as you vary the cathode current with the bias adjustment pot. Plate voltage will decrease as cathode current (or plate current) increases and vice versa. The plate voltage at 19.62 mA cathode current will not be the same as the plate voltage at 35.96 mA cathode current.

+310 VDC/+330 VDC measured where?

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Post subject: Re: Super-Sonic 22 Bias Level
Posted: Wed Jan 16, 2013 7:34 am
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bluesky636 wrote:
The different values of plate resistors on the PIs of the SS 22 and DRRI have only a minor effect on the inverted/noninverted gain values of the two PIs. They have no effect on biasing the power tubes.

The plate voltage does not remain the same as you vary the cathode current with the bias adjustment pot. Plate voltage will decrease as cathode current (or plate current) increases and vice versa. The plate voltage at 19.62 mA cathode current will not be the same as the plate voltage at 35.96 mA cathode current.

+310 VDC/+330 VDC measured where?


PINS 3 > 8 (well of course you are right any body that has monitored bias and swung a signal can see that)...but my testing so far on the ss22 is quickie stuff to verify the tubes worked and the chip changes didn't cause problems and t let me treat all connector (ALL) stay tuned :shock:

but last night i mad changes and am now at 24mvdc at the bias test points and seeing (with 122.2vac line voltage) (approx 340 there last night (cold tubes and a quickie)...today i will do some real measurements and my bud is coming with speakers, and 1 ohm 2watt resistors (1w needed) for the vibro king

i have been swapping tubes and current i havce waht appears to be an unblaned pair (i bought a quartet) so i'll swap some 6v6's around to see if i can get closer matching (all resistances and signls are spot on..so i'll move tubes...but seriso testing to take place today

nerd fest when norm comes he gets really really into this stuff.....man he has some sweet amps and he doens't want to hassle marketing them but darn they sound good....

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Post subject: Re: Super-Sonic 22 Bias Level
Posted: Thu Jan 17, 2013 9:39 pm
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Just wanted to report back that I didn't die or get electricuted and I successfully biased the amp!
Thank you all for your help! I would never even attempted it without this thread.

My plate Volatage was right on - 415
And my bias was WAY off - I believe it was 36 mV! I put in JJ 6V6S like I mentioned, and the tubes were a little off from each other as expected but I cooled the bias down to 24.7 on one tube, and 23.6 on the other.

The amp plays and sounds great! I hope to post a video, I recorded the steps.
Thanks again!


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Post subject: Re: Super-Sonic 22 Bias Level
Posted: Thu Jan 17, 2013 9:57 pm
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Glad it worked out, ok. However, I watched your video on biasing and got this. Missed the biasing part. :D


http://www.youtube.com/watch?v=lyViVmaBQDg


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Post subject: Re: Super-Sonic 22 Bias Level
Posted: Thu Jan 17, 2013 10:33 pm
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eriwebnerr wrote:
Just wanted to report back that I didn't die or get electricuted and I successfully biased the amp!
Thank you all for your help! I would never even attempted it without this thread.

My plate Volatage was right on - 415
And my bias was WAY off - I believe it was 36 mV! I put in JJ 6V6S like I mentioned, and the tubes were a little off from each other as expected but I cooled the bias down to 24.7 on one tube, and 23.6 on the other.

The amp plays and sounds great! I hope to post a video, I recorded the steps.
Thanks again!


Excellent. One mA difference is not bad. After several hours of playing, go back and check the bias again and readjust if necessary.

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Post subject: Re: Super-Sonic 22 Bias Level
Posted: Thu Jan 24, 2013 1:17 pm
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eriwebnerr wrote:
Just wanted to report back that I didn't die or get electricuted and I successfully biased the amp!
Thank you all for your help! I would never even attempted it without this thread.

My plate Voltage was right on - 415
And my bias was WAY off - I believe it was 36 mV! I put in JJ 6V6S like I mentioned, and the tubes were a little off from each other as expected but I cooled the bias down to 24.7 on one tube, and 23.6 on the other.

The amp plays and sounds great! I hope to post a video, I recorded the steps.
Thanks again!



this is one of the weird things tubes amps are known for...so i put two perfectly matched (??) genalex 6v6 in and had differing levels of bias at the bias test points (i installed copper loop to allow easy measurement..so i just swapped tubes in their respective locations and they are within .1 mv...nice and balanced...

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Post subject: Re: Super-Sonic 22 Bias Level
Posted: Sun Oct 27, 2013 6:18 am
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Sorry to resurrect this but...

I've just bought a used Super-Sonic 22 - all Groove Tube valves/tubes.

Plate voltage measured at pin 3 on the 6V6's is 445v (I'm in the UK)

So if Fender suggest 24mA based on 420v then this indicates 0.024 x 420 = 10.08w

So 10.08w / 445v = 0.022 so I've set the bias as 22mV (mA)

Does that sound right please ?

Thanks,

Glenn


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Post subject: Re: Super-Sonic 22 Bias Level
Posted: Sun Oct 27, 2013 6:35 am
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22mA (0.022 amps) times 445 VDC = 9.79 watts. Pretty close to your 10.08 watt nominal value. A good starting point. Be sure tubes aren't red plating. You should be good to go.

Good luck! :D


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Post subject: Re: Super-Sonic 22 Bias Level
Posted: Sun Oct 27, 2013 9:01 am
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Thanks,

I played at home volume for an hour or so with no sign of red plating so hopefully all is ok.

I traded an original black Super-Sonic 112 (60w) in for the 22w and it is a much better sounding amp to my ears... particularly the vintage channel(s).

Rehearsal on Thursday should be good !


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Post subject: Re: Super-Sonic 22 Bias Level
Posted: Sun Oct 27, 2013 12:20 pm
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hallgn wrote:
Sorry to resurrect this but.....


Actually, thank you for taking the time to do a search and using the thread to keep the info together, which might make things easier for the next person. 8)

Welcome hallgn! :)

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