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Low Voltage on Pin 7!?


Zoki

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Hey Gang,

 

Well, I decided to go ahead and check the voltage at pin seven on my voxy mod and surprised to find that the thing is reading about 290 - surprised because after doing my marshall mod the digits came in right around 300....

 

So my questions are -

 

What does this mean to the tone of my amp and how it's running?

 

Does it possibly explain the harsh high end that the conjunctive filter helps tame?

 

How do I go about tweaking it?

 

And I guess while I'm at it, after checking my work to make sure I'd gotten all the right caps and resistors in the right places I'd noticed that the spec on the vox mod for R15 is 56k - which seems awfully high given that the rest of the mods have R15 somewhere between 5.6 and 10k.......any thoughts or explanations on that?

 

Alright, well there's some food for thought,

 

Again, thanks in advance for ya'lls help and insight!

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  • 3 weeks later...

Hey Gang,

 

Just wanted to give this old question a bump...

 

Read enough to figure out that 56k seems to be the going value at r15 but am still wondering what the 290 I got at pin 7 means to the way my amp is running and if it's something I should look into tweaking...

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290 on the plate isn't necessarily bad, just lower than what everyone else is shooting for. And even then, it's not really very low. My Crate VC508 had 270v on the plate, and I used to think it was plenty crunchy. Till I got to tweaking the VJr's, that is. What's your voltage at B1?

 

The 56k in R15 is gonna trim a lot of the high end. I usually like 5k or 10k max in R15.

 

Gil...

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Hey Gil,

 

Thanks for the response - you know part of thing i was concerned about was the low voltage was resonsible for that "harsh" high end some of the guys had talked about over on SEwatt - which of course I hadn't even really noticed or thought and am now on a quest to conquer. The Conjunctive Filter mod seems to actually do the trick, but I was kinda losing a bit too much high end on my hummers while smoothing it out - even messing with the cap values. Soo maybe I'll work on R15 with the CF in the circuit and see what I'm coming up with...

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