TWANG Posted February 18, 2009 Posted February 18, 2009 whatcha think.. even swapped to a 500K pot.. soon a I hit any volume at all.. I'm breaking up. 8:00 on the dial. also, low notes.. kinda muted sounding.. and it's compressing a lot. I didn't do much, C6 went up new spragues.. 2.2 and 4.7 electros.. 100K r6/7 c5 1000uF R10 to.. now I've forgotten. .the usual marshall value. r1 1M r2 10K that's about it. man it breaks up early.. lost some highs wired a cap over R6, 500pF haven't tested. guess I'll have to.. 7.5k ot. shoulda planned this out instead of winging it. *L* whatcha think? TWANG
m-theory Posted February 19, 2009 Posted February 19, 2009 whatcha think? Gut the pig and build an octal or baby will.
lostindesert Posted February 19, 2009 Posted February 19, 2009 Don't use Chinese pre-amp tubes, go for Electro-Harmonix, JJ/Tesla, Sovtek LPS or NOS. Peter
m-theory Posted February 19, 2009 Posted February 19, 2009 9th gen chinese 12ax7s are actually pretty good, although preamp tube country of origin isn't the problem with Twang's amp. It sounds to me as though the tubes aren't biased properly, although I personally find it a complete waste of time to do anything with a V1 or V2 Vjr except gut the pig and build it into something useable.
TWANG Posted February 19, 2009 Author Posted February 19, 2009 I think I'll go backwards first.. that distortion showed up at about the third change... then I'll check voltages.. and maybe I'll use this 5K ot when the dirt is out.. then try to get voltages good..and move forward again. I don't want to rebuild the whole thing really. thanks! TWANG
m-theory Posted February 19, 2009 Posted February 19, 2009 I don't want to rebuild the whole thing really. This is where you're going to end up anyway, so you might as well take the easy/cheap/short cut route, and just gut the pig to begin with. You KNOW you're going there eventually anyway.
TWANG Posted February 19, 2009 Author Posted February 19, 2009 Nope. I'll take it back to stock before I do that. TWANG
TWANG Posted February 19, 2009 Author Posted February 19, 2009 ack. I lost my printout of the test points. was that a sewatt thread? TWANG
TWANG Posted February 19, 2009 Author Posted February 19, 2009 went at it by memory.. ax7 1...177 3.... 1.38 4/5 ......6.92 6.....175.3 8.....1.4 el84 3......10.17 5... 6.72 7.... 297.3 9...289.6 r10 314 r12 289 r3 270 seems pretty good for numbers for such a terrible sound. heaters a little high.. TWANG
TWANG Posted February 19, 2009 Author Posted February 19, 2009 swapped C1 to .015uF. highs came in nice.. finally right in that deptartment. took out the sovtek el84 and EH ax7 I had in it.. put in chinese 84 and sovtek ax7 sounds great! part of the yuck must have been one of those tubes. I think the cap over r6 did less for treble than the .015 at C1. But it's hard to tell since I only heard that with a crap tube. Now I think I should look up the diode part no. from rat shack.. hope I saved it, to get the heaters down a bit. Isn't there a resistor fix for that, too? maybe I'll stick an nfb on it just to spruce up the panel. TWANG
Eracer_Team Posted February 19, 2009 Posted February 19, 2009 I think you're a little under on the el84 pin 7 & 9 (everything else looks good) I like those closer to 310/300 than were you have both under 300. But that's just me.
TWANG Posted February 19, 2009 Author Posted February 19, 2009 Yeah, me, too. I was pretty ok with what it sounded like, but I may tweak a bit yet. I'm still thinking of putting as SGR in so that would be the time. TWANG
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