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Tom M
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Joined: 25 Jun 2009
Posts: 128
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gtrplr71,,,hey man your amp tech is wrong. I am absolutely positive one trim pot is for right power tube and the other trim pot is for the left powertube. Absolutely positive, I have bias'd this amp 3 time's already. Next thing up, I tried to view your pic of your meter but I just seen a bunch of beautiful guitars and amp's. That strat is the sexiest I have ever seen, the light blue one. Send me a pic of your meter and I can try to help you, I don't feel comfortable having you stick your hand's in your amp if you don't remember how to setup your meter though, no offense but senior moments kill people and ruin families.
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Tom M
Level I

Joined: 25 Jun 2009
Posts: 128
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One of those pics I see 2 nice JJ powertube's is there something wrong with those? I know the amp ships with ruby's stock, but ruby's are just rebranded sovtek's I believe. If i am wrong on the brand somebody please correct me, I know they are rebranded something, there is only a few major tube factories left. Again nice pic's you have there, nice gear man
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gtrplr71
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Joined: 25 Oct 2008
Posts: 25
Location: Austin Tx
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I solved the meter i now have is a greenlee that measures in mA the blue guitar is my 1957 AVRI it is sexy. that is actually my last amp SV heavily Modded.
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Tom M
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Joined: 25 Jun 2009
Posts: 128
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My meter measures that way too so you want to adjust them tubes to about 34-35mA, on the meter it looks more like this .034, just move the decimel in your head and you got it. The black lead stays pushed against the center pin while the red lead touches right or left pin, right pin is right tube, left etc... when you get a reading depending on wether it need's to go up or down, that's when you take a little screwdriver and carefully turn the little brass screw on the square blue trim pot. One direction makes it go up, the other direction down. Now everytime you move the screw, take a reading and see where your at. WHat is going to happen is the other tube will be affected as well and go up or down a little, usually down. All you do is go back and forth until you have both tubes at 34-35mA's and then keep it idling there with amp on for about 10 minutes and recheck. I always play through mine for awhile then recheck to see if it moved, because it does a little, then I just repeat steps then put chassis back in head and jam away. Let me know if you have any questions or concerns, Using a bias probe that fits in the tube socket takes some of the fear out of doing this but I can pretty much say that where those trim pots are you will be fine. Always keep 1 hand free, as to not make ground and you should be good. Good LUck
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timowens
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Joined: 03 Jun 2010
Posts: 30
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gtrplr71 wrote:
I solved the meter i now have is a greenlee that measures in mA the blue guitar is my 1957 AVRI it is sexy. that is actually my last amp SV heavily Modded.


Just to be clear on this, if you are using the bias test points in the Alchemist to measure/set the bias you are NOT measuring mA, you are measuring mV and converting that to mA mathematically.
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gtrplr71
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Joined: 25 Oct 2008
Posts: 25
Location: Austin Tx
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OK just heard back from my tech bias points are done he is going to clean up the preamp a little and open the amp up a little more sparkle and sizzle in the gain channelso what I will end up with is something that sound like an XTC should be sick he is taking a bunch of photos and mapping the board. So I will sell you guys mods when I get the amp back Just kidding I will post clips soon!
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Tom M
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Joined: 25 Jun 2009
Posts: 128
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can't wait too hear how you make out,, Is there anyway you can post soundclips?? Picture's would be cool as well.. These are the kind of mod's that make these amp's like the custom one's,, buy bogner not already putting these test points back there he kept the price down. Your going to love having those there.
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gtrplr71
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Joined: 25 Oct 2008
Posts: 25
Location: Austin Tx
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sure I will post clips this weekend should be just wicked
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 bias probe reading different than test pin reading 
Guitarted
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Joined: 10 Jul 2010
Posts: 9
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deleted


Last edited by Guitarted on Sun Nov 28, 2010 3:19 pm; edited 1 time in total
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 bias probe reading different than test pin reading 
Guitarted
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Joined: 10 Jul 2010
Posts: 9
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I just biased my Alchemist using Tom M's instructions . It all worked fine (although it seemed to me I had to turn the trim pots counter clockwise to increase the bias, unless to pot on the right is for the left tube). Thanks Tom.

My amp was set at 33mA and 32mA from the factory. I used the test pins inside the chassis to set the bias to 35ma on both tubes. I also have one of those tube bias probes that you plug in between the socket and the tube. After I set the bias using the test pins I took a reading with the bias probe and the reading was 4 mA higher than I got using the test pins. That was a bit disconcerting. I am sticking with readings from the test pins. Tom or anyone else, have you experienced this type of discrepancy between a bias probe reading and test pin reading? Confused Thanks
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Tom M
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Joined: 25 Jun 2009
Posts: 128
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I want to say I may have screwed up writing the counteclock and clockwise thing, sorry. I will have to fix that. Glad you figured it out.

As far as my bias probe reading different than my test points, I want to say they were off 1 or 2 but def not 4, did you give it time to settle down, it does move alot for some reason
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sahlomonic
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Joined: 11 Apr 2010
Posts: 17
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Tom M -

Followed your bias instructions. Yes, it is identical to biasing a Marshall JCM2000 DSL, so this was familiar territory for me. Factory bias on the Alchemist's Ruby tubes were 28mv, and popping in =C= 6L6GC tubes resulted in 43mv from the start. It seems that =C= tubes just run hotter, because with my Marshall DSL I put in a quad of =C= EL34s and they were almost redplating before I biased them; had to turn the bias way down to get them within spec.

Thanks!!! Very Happy
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Carvin Knight
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Joined: 06 Jul 2010
Posts: 70
Location: San Antonio Texas
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Same thing here. I was at 35ma with the gt6l6s and after dropping in the winged Cs it jumped to 50ma. That's from 50% to 70% at idle. quite a jump. Now I'm on 36ma.

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I dig my Bogner Alchemist 112
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Guitarted
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Joined: 10 Jul 2010
Posts: 9
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Tom
I did run the amp for 10 minutes or so before I took the reading with bias probe. I only did it once however. Maybe I'll try it again with another amp and see what happends
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Tom M
Level I

Joined: 25 Jun 2009
Posts: 128
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Cool, it's great to hear it's working out for people. I've been so busy, I really want to get a video bias'ing my own alchy. Maybe tough getting the camera angles by myself. Maybe i'll have jr help me:p
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