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sumitomo
July 29th, 2009, 03:01 PM
I am upgrading my output trans in my valve jr and I am going to use a blackfack champ ot.I can't read the paper they sent it is blurry.I know I will lose the 16 ohm output.I got it from Mojo anyway on the VJ the white is 0 yellow is 5.2ohm/the outs are blk common(I know where that goes)4 ohm is brn and 8 ohm is red org is 16 ohm on the new OT red and blue are going where white and yellow are and green I think is the 8 ohm and yellow is the 4 ohm.Oh yea Mojo part # is 771 any help would be great.Thanks Sumi:D
Oh yea Mine is a newer head with the black pc board and I bought it new,sounded ok to me and I thought a OT upgrade might help and guess what it came stock with JJ's.

tunghaichuan
July 29th, 2009, 06:06 PM
Sumi,

I have a schematic for the Gibson GA-5 reissue, which uses the Mojo 771 OT, but unfortunately it doesn't indicate which colors are which.

I do have a photo of the guts of the GA-5 and it looks like the red and blue are the plate and B+ leads on the mojo, which correspond to the white and yellow wires on the VJ OT.

The yellow wire is probably the 4 ohm lead on the Mojo 771 as it is wired to the output jack. It is hard to see where the green wire is going, but I believe it is the 8ohm tap. The black wire on the 771 looks like it is grounded.

Hope this helps.

tung



I am upgrading my output trans in my valve jr and I am going to use a blackfack champ ot.I can't read the paper they sent it is blurry.I know I will lose the 16 ohm output.I got it from Mojo anyway on the VJ the white is 0 yellow is 5.2ohm/the outs are blk common(I know where that goes)4 ohm is brn and 8 ohm is red org is 16 ohm on the new OT red and blue are going where white and yellow are and green I think is the 8 ohm and yellow is the 4 ohm.Oh yea Mojo part # is 771 any help would be great.Thanks Sumi:D
Oh yea Mine is a newer head with the black pc board and I bought it new,sounded ok to me and I thought a OT upgrade might help and guess what it came stock with JJ's.

jim p
July 29th, 2009, 06:38 PM
Just to ask but Mojo has an 800 number so why not call to ask for a better schematic for the transformer. Maybe they can just e-mail you a pdf. So you don’t risk hooking it up wrong. Also how much does the transformer weigh on the web site it states a weight that must be wrong?

sumitomo
July 29th, 2009, 08:10 PM
Thanks Tung and Jim,I know where all the one's go but the blue and red which I thought was plate and + so I'll call tomorrow.I just got through putting a OT in my B Junior and twisted wires ect.,found out something,the tube on the end(only tube closest to the side of the amph,well it was a little microphnic,so I was trying other tubes ect,I noticed the ribbon the connects to the socket if I close my fingers around it more hum so later I'll slice it and weave them apart and report back other than that it Rock's:rockon:Sumi:D P.S.these are just Heyboyer OT's

sumitomo
July 30th, 2009, 08:08 AM
Blue is the plate to the el84/red +.So Blue would replace the yellow and red to where the white or Blue to t3 and red to t4.Sumi:D