Messed up R2 volume mod, ideas?

[CoG]

Hi guys---

So I went in to do the R2 volume mod on my green stripe. I did the "compromise" version, using the direct pot.

The mod works exactly as advertised for R2 volume, but I have lost a ton of preamp volume, seemingly from R1.

R1 sounds like I have the Volume set at 3 instead of 7.

R2 and Lead sound "right", just too quiet and a bit thin, again like the Volume is set low.

I can tell from the wattage meter on my Palmer that my output is way down at my normal settings.

Changed the V1 and V2 tubes, no effect, plugging into the fx return indicates that the power section is working fine (I can spike it up past 60W according to the Palmer.)

There's no added noise, clicking, dropouts, or anything, just this seeming lack of gain from the R1 stage.

Could this be a bad solder joint starving the signal (I'm not a star with the iron by any means) or do I need to use a different pot instead of re-using the direct pot?

 

[camsna]

Could be a combo of the two.

BUT!

You need a new pot! I think the presence is 1 MEG! You need a 250K audio taper pot.

I got one from Mesa. The part was, like, 3 bucks. But shipping was 7. HA! Can't recall the part number, though. Sorry. I just asked for a presence pot only 250K.

 

[CoG]

I used the DI output pot. which helpfully hasn't got a value on it :roll: For some reason I thought you could just re-use that pot.

I'm thinking it's gotta be the pot value because it sounds okay, it's just too quiet. If I had a bad joint shouldn't it be noisy or intermittent?

 

[camsna]

Not necessarily. Bad joints are like little gremlins in your electronics. They cause all KINDS of unexpected havoc. I'd reflow them just to be sure.

Cam's unorganized tips for soldering:

1) Use 'enough' solder. NOT TOO MUCH! But enough. If there's too much - use a wick or a sucker to remove the solder and do it over.
2) Heat the part - not the solder!
3) Make sure that the solder is completely liquid before moving the iron away
4) NEVER blow on a solder joint to cool it down. Let it cool on its own. This is probably the most common cause of cold joints.
5) When you're done - the joint should be silvery and shiny. If it's dull and gray - do it over.

Hope this helps! Also - if you wanna be sure it's the pot - head to your local Guitar Center. They'll have 250k audio pots. Radio Shack won't... Anyhow. Pick one up! Only a couple of bucks.

 

[CoG]

See, that's what I thought. I'm no pro but I have rewired a couple guitars and done the basic Epi VJ mods, and I've made a bunch of cables, so I didn't think I'd mess up the soldering.

Sure enough, ran down to the store, grabbed a 250K audio taper, and I'm in business.

So for future reference, you CANNOT re-use the direct out pot for your R2 volume... :lol:

 

[camsna]

SCHWEET!

Glad to hear it's working!!!!

 

[GIG4FUN]

So glad! Nothing hurts more than to mess something up with the intentions of doing something better! I have had had them bowl of wheaties before! I'm happy for you!

R2 vol mod...It makes the amp perfect in my view. :wink:

 

[CoG]

Thanks guys, Cam especially!

Yeah, it's another way to tell that the green stripe is *really* different from the purple. On the green, R2 volume at 8 is LOUD. If the master's at 3, it's loud as hell and there's LOT of power-tube crunch happening on R2. You could pretty much use it for rhythm for anything up to, say, Tool. I need the lead master at like 7.5 to match!

R2 on the purple hasn't got near as much gain.

 

[Restless Rocks]

The R2 pot should switch completely out of the circuit when in R1 and Lead channels. If turning the pot has an effect when you are anywhere except R2 then you have wired it incorrectly.

 

[CoG]

No, turning the pot had no effect outside of R2. Jyst the fact of the pot's existence apparently cut the volume of the whole preamp section by a fixed amount. Go figure.

Anyway, it's all good now with a 250K audio taper. My purple had the R2 done by Mike B and my green works the same now... well, the same but "more" because of the different voicing of R2 on the green stripe.