SRS Biastool instructions

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SmokestackElRopo
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SRS Biastool instructions

Postby SmokestackElRopo » 30 Dec 2017, 16:13

Does anyone have the instructions for an SRS Biastool PVT, and the SRS Dual bias tool?
Guitarz; Epiphone Les Paul Ultra w/490R and 490T on the bridge
Gibson Les Paul supreme Goldtop 2007 GOTW 22 w/57 classic and 57+ on the bridge
Epi Dot Deluxe
Ampz; All Marshall ; JTM 45
Valvestate VS102
JCM 2000 DSL 100
JCM 2000 DSL 401
Vintage Modern 2266C
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Re: SRS Biastool instructions

Postby Anitoli » 30 Dec 2017, 17:49

According to their site you will need to determine whether you have the Mv or Ma type of probe and what your meter will read:

.There are many types of BIASTOOL test probes available: Version 1, the original BiasTool mA, is for owners of meters which can read current in DC mA directly, Version 2, the BiasTool mV, which is designed for owners of meters which do not have the capability of reading current directly, as well as the DualBiasTool, which utilizes two of our mV probes and a rugged switchbox- this unit tests two tubes at a time, or both sides of a push/pull amplifier without powering down and switching tubes or sockets!

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Re: SRS Biastool instructions

Postby SmokestackElRopo » 31 Dec 2017, 13:43

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Anitoli, Are you affiliated with SRS? You say 2 of "our" mV probes is thereason I ask. Here are pics of what I have.
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IMG_1382.JPG
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Guitarz; Epiphone Les Paul Ultra w/490R and 490T on the bridge
Gibson Les Paul supreme Goldtop 2007 GOTW 22 w/57 classic and 57+ on the bridge
Epi Dot Deluxe
Ampz; All Marshall ; JTM 45
Valvestate VS102
JCM 2000 DSL 100
JCM 2000 DSL 401
Vintage Modern 2266C
Pedalz; Dunlop 535Q wah and Voodoo Labs Amp amp selector Boss delay.

SmokestackElRopo
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Re: SRS Biastool instructions

Postby SmokestackElRopo » 31 Dec 2017, 13:45

What you see are the only identifying marks on these tools.
Guitarz; Epiphone Les Paul Ultra w/490R and 490T on the bridge
Gibson Les Paul supreme Goldtop 2007 GOTW 22 w/57 classic and 57+ on the bridge
Epi Dot Deluxe
Ampz; All Marshall ; JTM 45
Valvestate VS102
JCM 2000 DSL 100
JCM 2000 DSL 401
Vintage Modern 2266C
Pedalz; Dunlop 535Q wah and Voodoo Labs Amp amp selector Boss delay.

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Re: SRS Biastool instructions

Postby Anitoli » 31 Dec 2017, 14:13

No i an not affiliated with them, the bottom part was quoted from their site. From your pic you have the Dual Bias Tool which their page states has "two Mv Probes" which i would take to mean that it measures the millivolts across the cathode by inserting a one ohm resistor in series with the cathode. The problem with this is that unless you know what the anode voltage is the Mv reading is useless. The Mv reading will need to be converted to Ma then multiplied by the anode voltage to give you the plate dissipation. Some people add 5Ma to account for the screen grid current that also flows through the tube.

These probes were designed to make biasing easy and safer but without knowing the plate voltage you are in the dark.

The formula for figuring out dissipation is V x C = P. For example, if your plate voltage is 460 and your current reading is 35Ma ( .035) you get
460x.035 = 16.1 watts. Now say the plate voltage is 480. This is what you get, 480 x .035 =16.8 watts. Not really a huge difference but now let assume we add in the screen grid current of 5 Ma, now we get 460 x .040 = 18.4w watts. now plate voltage at 480, 480 x .040 = 19.4 watts.
As you can see the difference in the plate voltage and the current makes a big difference in the final reading.

Now you need to remember that the power tube has a point at which it gets too hot current wise. The standard value to stay below is 70% of MAX dissipation. So if you are using a 6l6GC tube which is rated at 30 watts, your 70% number would be no more than 23W. For any tube going beyond the 70% zone will runs then very hot and shortens the life of the tube quite a bit. If you go past say 85% you start running the risk of red plating and the tubes life is measured in minuets.

This is from my site dealing with Marshall 6100's but this can be applied to many amps as long as you can solder and get to the tube sockets and can safely work around high voltages. It is a little more involved taking the chassis out to bias but on most amps you have to take out the chassis anyway because the bias adjustment pot is on the power amp board inside! With this method you just leave the resistors in there. Go to the page biasing a 6100.

http://home.myfairpoint.net/vze1u14s/pe ... rtservice/

Hope this helps.

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Re: SRS Biastool instructions

Postby SmokestackElRopo » 31 Dec 2017, 18:14

I failed a KT66 in my Vintage modern 2266C. I have a supposedly matched quad of valve arts and a supposedly matched pair of Groove tubes KT66HPz. None of these tubes are matched at all, when rotated in/out with the dual bias tool inline. probably should take it to a pro. Thanx much for your reply, but my math skills leave much to be desired. I'm really dumb when it comes to math.
Guitarz; Epiphone Les Paul Ultra w/490R and 490T on the bridge
Gibson Les Paul supreme Goldtop 2007 GOTW 22 w/57 classic and 57+ on the bridge
Epi Dot Deluxe
Ampz; All Marshall ; JTM 45
Valvestate VS102
JCM 2000 DSL 100
JCM 2000 DSL 401
Vintage Modern 2266C
Pedalz; Dunlop 535Q wah and Voodoo Labs Amp amp selector Boss delay.

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Re: SRS Biastool instructions

Postby Anitoli » 31 Dec 2017, 18:50

The 2266 has the bias adjustment pins already in the amp. In the photo enclosed the bottom arrow points to the measurement pins and the top arrow for the adjustment. You place the red lead on either outside pin and the black lead on the middle pin with the meter set to read millivolts. The target for these amps is 48Mv. What you try to do is balance the reading between both sides as closely as possible.
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SmokestackElRopo
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Re: SRS Biastool instructions

Postby SmokestackElRopo » 04 Jan 2018, 18:43

OK I have taken the dual bias tool out of the equation. The readings now are KT66 1=456 Kt66 2= 256. This follows any KT66 I put in. tube 1 is high and tube 2 is low. I only have 1 trim pot. this unit was made April 2008 and was bought as new from MF. It has functioned up to now very well.
Guitarz; Epiphone Les Paul Ultra w/490R and 490T on the bridge
Gibson Les Paul supreme Goldtop 2007 GOTW 22 w/57 classic and 57+ on the bridge
Epi Dot Deluxe
Ampz; All Marshall ; JTM 45
Valvestate VS102
JCM 2000 DSL 100
JCM 2000 DSL 401
Vintage Modern 2266C
Pedalz; Dunlop 535Q wah and Voodoo Labs Amp amp selector Boss delay.

SmokestackElRopo
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Posts: 21
Joined: 22 Apr 2009, 14:12
Location: Oklahoma City, OK USA
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Re: SRS Biastool instructions

Postby SmokestackElRopo » 06 Jan 2018, 09:10

Reinstalled Bias tool inline and 2 out of 6 tubes biased up. Good to go.
Guitarz; Epiphone Les Paul Ultra w/490R and 490T on the bridge
Gibson Les Paul supreme Goldtop 2007 GOTW 22 w/57 classic and 57+ on the bridge
Epi Dot Deluxe
Ampz; All Marshall ; JTM 45
Valvestate VS102
JCM 2000 DSL 100
JCM 2000 DSL 401
Vintage Modern 2266C
Pedalz; Dunlop 535Q wah and Voodoo Labs Amp amp selector Boss delay.

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