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Post by scottunzicker on Jul 27, 2017 8:39:08 GMT -7
Howdy all. I'm seeking opinions and speculation about what may have happened to my Z-Lux the other night in the middle of a gig. The setup: I had my Nocaster plugged straight in to the Z-Lux (no pedals) on full power, master all the way up, pre-volume about 11 o'clock, with the boost about halfway dialed up. About an hour into the gig, the amp just stopped making any audible noise at all, but the pilot light stayed on. No amount of knob twiddling had any effect. I put the amp on standby, removed my homemade boost knob (and this is the part about which I'm suspicious), turned the standby switch back on, and voila, it worked, and has been working ever since (three gigs later). In short, I'm seeking speculation about what may have happened, and I also really want an evaluation from y'all about the efficacy of the homemade boost knob I've been using (see pix below). Thanks for your time and expertise. Cheers!
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Post by BritInvasion on Jul 27, 2017 10:35:09 GMT -7
Interesting boost control you have there. I would suspect that having that plugged into a roaring combo could induce enough vibration in the potentiometer that the wiper may have shaken loose internally and created an open circuit - no sound.
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Post by Maddog on Jul 27, 2017 11:52:14 GMT -7
Ingenious boost control there, unfortunately, it's probably the problem. Totally agree w/ Frank, but also check yer speaker wires, plugs, and contact clips....
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Post by scottunzicker on Jul 27, 2017 12:37:37 GMT -7
Thanks, gents. Maybe I could use some sort of rubber ring around the leads of the 1/4" male plug and clean the dickens out of the pots. Glad you like the boost solution. Do I have it soldered up correctly, from what y'all can tell?
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Post by nicholas on Jul 27, 2017 12:53:52 GMT -7
The boost is just lifting a ground, or making a ground. The pot is just making it variable. Amp works either way whether you unplug it, shunt it, or put a variable pot in it. I don't see how that could be your problem.
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Post by BritInvasion on Jul 27, 2017 13:56:36 GMT -7
The boost is just lifting a ground, or making a ground. The pot is just making it variable. Amp works either way whether you unplug it, shunt it, or put a variable pot in it. I don't see how that could be your problem. Agree , but are his connections right? The wiper (or slider) and 1 end of the resistive track are soldered together on the + side , the other end of the resistive track is soldered to the - (ground) side. If the connection for the wiper comes loose , he now has a big resistor sitting in the circuit. That's how I'm seeing it , and of course I could be wrong.
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Post by scottunzicker on Jul 27, 2017 14:04:36 GMT -7
The boost is just lifting a ground, or making a ground. The pot is just making it variable. Amp works either way whether you unplug it, shunt it, or put a variable pot in it. I don't see how that could be your problem. Agree , but are his connections right? The wiper (or slider) and 1 end of the resistive track are soldered together on the + side , the other end of the resistive track is soldered to the - (ground) side. If the connection for the wiper comes loose , he now has a big resistor sitting in the circuit. That's how I'm seeing it , and of course I could be wrong. Thanks for the observations, BritInvasion. That's just the sort of feedback for which I'm looking. Do I have the pot soldered up properly to the 1/4" plug? Does anybody have the variable boost footswitch they've opened up for comparison?
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Post by Maddog on Jul 27, 2017 16:03:53 GMT -7
Agree , but are his connections right? The wiper (or slider) and 1 end of the resistive track are soldered together on the + side , the other end of the resistive track is soldered to the - (ground) side. If the connection for the wiper comes loose , he now has a big resistor sitting in the circuit. That's how I'm seeing it , and of course I could be wrong. Thanks for the observations, BritInvasion. That's just the sort of feedback for which I'm looking. Do I have the pot soldered up properly to the 1/4" plug? Does anybody have the variable boost footswitch they've opened up for comparison? There are a few old threads stating how to make a variable footswitch out of a non-variable model, but all of the schematics on those are no longer visible (since photobucket changed its 3rd party hosting policy). It's very easy to do, even I (duh) converted one. If we could get one of those schematic pix up, you could use it to see if yours is connected correctly. However, the proof's in the pudding... ie: did it work? Meaning, it will either work or not depending on how it's connected. If your little device IS the culprit of temporary dead amp, I'm agreeing with BritInvasion (Frank) and assume the vibrations got to it, especially in a live (loud) playing environment. I'll keep looking and try to find the schematic for correctly wiring a pot in the switch circuit, but I don't have great faith I'll find one......in all the ones I found, the images were blank.... Good luck, brother!
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Post by nicholas on Jul 27, 2017 18:14:54 GMT -7
scottunzicker, I think there are two questions here. Is your variable switch causing a no-sound issue with your amp? I can't see any way that is possible. The device just takes a wire that is normally grounded on your tone stack for normal operation and lifts it with a resistor for boost. You could smash it with a hammer and it wouldn't affect your amp from making sound. It would probably not work for boost after you smash it though The way you have it wired is different. But it should work fine like that. Let me explain a little. Here is a picture of a pot. Note the three lugs and how they are connected. The two outside lugs are hooked to each end of the resistance strip. So let's call the center lug (wiper) the input and the outside lug on the left (a) the output. Lets say the picture illustrates the knob turned 1/4 clockwise and you measured the resistance between the center (w) and left outer lug (a), it would be 25% of the value of the pot right? Because the wiper is closer to the left. You are just measuring a small section of the resistor. Now leaving the knob in the same spot, now measure between the center and the right lug (B). You are now measuring a bigger piece of the resistor right? So you would be measuring about 75% of the pot value. So choosing which outer lug you use will just determine whether clockwise knob rotation is a reduction or increase. Well... Sort of... The wrinkle here is with audio taper pots. The resistive strip is is not linear. So using the incorrect outer lug would mess up the taper. Usually when a audio taper pot is wired backwards the taper starts off real slow and gradual until you get to the last little bit of travel, then it all comes on real fast. In the picture you posted it looks like you have the center lug soldered to an outer lug. Look at the image and picture that. Imagine A and W soldered together and measure between W and B. You would still measure 75% of the pot value. It should operate just fine that way for this application. Good luck trouble shooting the no sound issue.
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Post by BritInvasion on Jul 27, 2017 18:28:06 GMT -7
That's a great description Nicholas.
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Post by scottunzicker on Jul 27, 2017 18:31:48 GMT -7
scottunzicker, I think there are two questions here. Is your variable switch causing a no-sound issue with your amp? I can't see any way that is possible. The device just takes a wire that is normally grounded on your tone stack for normal operation and lifts it with a resistor for boost. You could smash it with a hammer and it wouldn't affect your amp from making sound. It would probably not work for boost after you smash it though The way you have it wired is different. But it should work fine like that. Let me explain a little. Here is a picture of a pot. Note the three lugs and how they are connected. The two outside lugs are hooked to each end of the resistance strip. So let's call the center lug (wiper) the input and the outside lug on the left (a) the output. Lets say the picture illustrates the knob turned 1/4 clockwise and you measured the resistance between the center (w) and left outer lug (a), it would be 25% of the value of the pot right? Because the wiper is closer to the left. You are just measuring a small section of the resistor. Now leaving the knob in the same spot, now measure between the center and the right lug (B). You are now measuring a bigger piece of the resistor right? So you would be measuring about 75% of the pot value. So choosing which outer lug you use will just determine whether clockwise knob rotation is a reduction or increase. Well... Sort of... The wrinkle here is with audio taper pots. The resistive strip is is not linear. So using the incorrect outer lug would mess up the taper. Usually when a audio taper pot is wired backwards the taper starts off real slow and gradual until you get to the last little bit of travel, then it all comes on real fast. In the picture you posted it looks like you have the center lug soldered to an outer lug. Look at the image and picture that. Imagine A and W soldered together and measure between W and B. You would still measure 75% of the pot value. It should operate just fine that way for this application. Good luck trouble shooting the no sound issue. Nicholas, you are my HERO. Thank you, my friend. If you ever find yourself in my town (Austin), the first couple of rounds are on me, my man. Thank you for taking the time to explain all this!
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Post by BritInvasion on Jul 27, 2017 18:50:58 GMT -7
Electrical tutorials aside , I'm curious as to why you are using a plug-in pot instead of the variable boost footswitch? Do you prefer the boosted sound and just use this to dial in an always-on sweet spot?
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Post by scottunzicker on Jul 27, 2017 19:02:13 GMT -7
Electrical tutorials aside , I'm curious as to why you are using a plug-in pot instead of the variable boost footswitch? Do you prefer the boosted sound and just use this to dial in an always-on sweet spot? Frank - In short, I really dislike pedals, and my Z-Lux didn't come with the variable boost footswitch. Honestly, I only use the boost function with single coil guitars (specifically my Custom Shop strat and Nocaster). As you say, I like to find the "sweet spot" for me, and just use the guitar's volume and tone controls to do the rest. I'm going to de-solder the "extra" resistance strip lug and just leave the W lug and remaining strip lug and test it out. I'll test the response, and hope I get the "right" configuration to get a decent taper. If not, I'll switch stuff around and test again. Once again, thanks everyone for your help.
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Post by scottunzicker on Jul 28, 2017 7:13:47 GMT -7
So as you can see from the picture, I added a rubber grommet (actually, it's a straplock) to maybe dampen vibrations and a knob to add mass. If the knob looks familiar, it should; it's one of the knobs I replaced on the Z-Lux (I replaced the pre and master volume knobs with white chickenheads for easier visibility on a dark stage). Tonight, I will de-solder the lug circled in red. I am, indeed, using audio (as opposed to linear) pots, so I know I might get the weird taper. If I do, I'll swap them around. Once again, thanks for y'all's help!
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Post by benttop (Steve) on Jul 28, 2017 8:23:44 GMT -7
I don't see how this boost solution has anything to do with a dead amp symptom. The amp passes audio whether the tone stack is grounded or not. The pot goes from a dead short to a very high impedance, so an open circuit in the pot mimics high impedance, while a short mimics it's normal feature of shorting the tone stack to ground. I think you're chasing a ghost.
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Post by premiumplus (Dave) on Aug 2, 2017 18:01:25 GMT -7
I agree, there is no way that the boost circuit is causing the amp to go silent. And the way it's wired will work fine. If the boost control is reversed, and it gets less when turning clockwise, then just turn the jack around on the pot and re-solder it.
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Post by scottunzicker on Aug 3, 2017 7:30:16 GMT -7
Well, correlation doesn't prove causation, to be sure. I went ahead and de-soldered the lug on the pot I indicated above, and have played 5-6 gigs with the Z-Lux at this point with no problems. I absolutely noticed a difference in the "sweep" of the boost function when using the newly configured pot connections. Much better. I also opened up the amp and poked and prodded with a chopstick to make sure there were no loose connections, shot Deoxit in all the right places, etc., and found nothing wrong. In short, I have no idea what the heck happened, but it seems to have resolved itself. Rock on!
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Post by benttop (Steve) on Aug 3, 2017 19:43:11 GMT -7
I hate it when that happens...
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