Peavey 5150 choke mod

  • Thread starter Thread starter peterc52
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peterc52

peterc52

Well-known member
Should I do it?? What does really do? Who has done it?

Just ordered parts for the bias mod

Already did the Cameron mods. It sounds great.
 
I was gonna say, that amp works sick for a boost platform, but since you already modded/modding it, I would agree with @midnightlaundry, why not go all the way. Hope you made before and after clips! :cheers:
 
Here you go


Just in case, dude prefers his 5150 stock
 
I love the choke mod. That and the bias mod are the only two mods that amp needs, and the only mods my amp has.
 
Choke tightens the amp up big time once you get volume rolling.
 
Choke Mod? is that the one where i almost choked myself for selling a Mint Block letter back in 2008 for 800.00 & now i wish i would of kept it. The Amp literally looked like it just came out of the box. FUCK I'm dumb. :doh:
 
7 - 10 H is what you want. 150ma and 500v dc is fine.
Now....a couple of things to consider...
1 - you are replacing a 400ohm resistor for the screen supply with a 100 ohm coil. The stock screen grid resistors on the power tube board are 100ohms, so you will be lowering the effective screen grid value on each 6L6 to 200ohms, which is too low. I recommend you change stock screen resistors to 470ohms if you add a choke.

2 - OG 5150 / 6505 has standby switch between plate supply and the 400ohm resistor. This will leave one end of your choke disconnected in standby ( not good for choke lifespan). Standby switch should be relocated in circuit to before b+ to plates. Not as difficult as it sounds, and info is easily found with a web search.

My 6505 has bias mod and choke installed (10H) but I removed the "Cameron mods" as I preferred sound of stock circuit with choke and proper bias adjustment. I also changed all 1uf electrolytic cathode caps on small preamp board to 1uf polyester film. This helped to tighten up low end response. The electrolytic caps all measured around 1.5uf.
I also feel like film caps provide faster, tighter response vs electrolytic of the same value when used in cathode bypass applications.
 
That's why my amp pops when I flip the standby. I need to get mine rewired.
 
fusedbrain said:
7 - 10 H is what you want. 150ma and 500v dc is fine.
Now....a couple of things to consider...
1 - you are replacing a 400ohm resistor for the screen supply with a 100 ohm coil. The stock screen grid resistors on the power tube board are 100ohms, so you will be lowering the effective screen grid value on each 6L6 to 200ohms, which is too low. I recommend you change stock screen resistors to 470ohms if you add a choke.

2 - OG 5150 / 6505 has standby switch between plate supply and the 400ohm resistor. This will leave one end of your choke disconnected in standby ( not good for choke lifespan). Standby switch should be relocated in circuit to before b+ to plates. Not as difficult as it sounds, and info is easily found with a web search.

My 6505 has bias mod and choke installed (10H) but I removed the "Cameron mods" as I preferred sound of stock circuit with choke and proper bias adjustment. I also changed all 1uf electrolytic cathode caps on small preamp board to 1uf polyester film. This helped to tighten up low end response. The electrolytic caps all measured around 1.5uf.
I also feel like film caps provide faster, tighter response vs electrolytic of the same value when used in cathode bypass applications.
Click to expand...

Agree on all ends except the 470ohm screens. Just go to 1k ohm for screens as is done in Marshall’s. Your tube life will improve significantly and you’ll benefit from more of a pentode tone versus triode.

Absolutely everything said here is spot on and all things I’ve done to my 5150 as well.
 
Never owned a 5150 so I never thought about the fact that amp never had a Choke..
Will this just tighten up the feel with less sag? Does it change the highs and make it more aggressive??
 
midnightlaundry said:
Never owned a 5150 so I never thought about the fact that amp never had a Choke..
Will this just tighten up the feel with less sag? Does it change the highs and make it more aggressive??
Click to expand...
Cleans up the noise. Tightens it up significantly. Highs depends on how loud you crank on it. Bedroom levels you won’t hear a difference. Band levels you’re going to notice a whole different attitude on the resonance and presence controls.
 
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