Volume pot not working properly

Lower_48

Strat-Talk Member
Nov 29, 2021
27
Midwest
Well the build is coming along, and I've put everything together today only to find one head scratcher of a problem. I have a Freeway switch with independent tone controls and a Bourns sealed 300k volume pot with a 3.3m ohm resister across the hot and ground. After plugging it in and turning it up to 10 for tuning, I get no output. Knowing everything was wired according to the schematics, I started flipping switches and twisting knobs until I start seeing letters show up on the tuner. Good news! But then I find the problem is in my volume pot. Turning the volume all the way up or all the way down cuts off the power completely. Seems like a bad pot but I just wanted to run it by this group of experts to hear your thoughts. This is the first time I've used a 300k pot for volume with a resistor, and even though it's connected per the schematics I have no idea what it's supposed to accomplish except possibly drop the pots value to 274k and possibly brighten the tone a bit. Thoughts on why this volume pot drops out before it hits its stops on either end?

I've attached the wiring for the volume pot. The freeway with seems to be working properly so no need to add to the confusion.

Thanks and a bag of chips!
 

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Stephen James

Strat-O-Master
Vendor Member
May 30, 2016
513
Iowa City
Well the build is coming along, and I've put everything together today only to find one head scratcher of a problem. I have a Freeway switch with independent tone controls and a Bourns sealed 300k volume pot with a 3.3m ohm resister across the hot and ground. After plugging it in and turning it up to 10 for tuning, I get no output. Knowing everything was wired according to the schematics, I started flipping switches and twisting knobs until I start seeing letters show up on the tuner. Good news! But then I find the problem is in my volume pot. Turning the volume all the way up or all the way down cuts off the power completely. Seems like a bad pot but I just wanted to run it by this group of experts to hear your thoughts. This is the first time I've used a 300k pot for volume with a resistor, and even though it's connected per the schematics I have no idea what it's supposed to accomplish except possibly drop the pots value to 274k and possibly brighten the tone a bit. Thoughts on why this volume pot drops out before it hits its stops on either end?

I've attached the wiring for the volume pot. The freeway with seems to be working properly so no need to add to the confusion.

Thanks and a bag of chips!

No-load pots drop out on both ends.

So, per your description, are you saying that:
- you get 'sound' when the volume is in the middle of its range,
- but 'no sound' at both ends of its range (i.e. knob fully clockwise or counterclockwise)?

More questions:
- Does the taper seem appropriate?
- Do you have a multimeter to check the actual pot and resistor values?
- Do the tone knobs work as they should?
- Is the problem behavior exhibited in all switch positions?

Also, dropping the combined resistance value would darken the tone, not brighten. A 10% tolerance on the 300k pot means the pot may already be at 270k before even adding the resistor. And a 0.1uF tone cap would make the tone way way darker when using the tone knob.

Do you have any pics of the actual wiring?

I am also tagging @BuddhaFingas and @dirocyn as they helped you with this in your previous thread about this wiring scheme: What tone change occurs when using a 300k volume pot and 3.2M ohm resistor?

Let us know what you find..
 
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Lower_48

Strat-Talk Member
Nov 29, 2021
27
Midwest
No-load pots drop out on both ends.

So, per your description, are you saying that:
- you get 'sound' when the volume is in the middle of its range,
- but 'no sound' at both ends of its range (i.e. knob fully clockwise or counterclockwise)?

More questions:
- Does the taper seem appropriate?
- Do you have a multimeter to check the actual pot and resistor values?
- Do the tone knobs work as they should?
- Is the problem behavior exhibited in all switch positions?

Also, dropping the combined resistance value would darken the tone, not brighten. A 10% tolerance on the 300k pot means the pot may already be at 270k before even adding the resistor. And a 0.1uF tone cap would make the tone way way darker when using the tone knob.

Do you have any pics of the actual wiring?

I am also tagging @BuddhaFingas and @dirocyn as they helped you with this in your previous thread about this wiring scheme: What tone change occurs when using a 300k volume pot and 3.2M ohm resistor?

Let us know what you find..
The knob function is a great question. Since the volume drops out and all I did was root cause that I haven't actually played through it yet to hear any sounds. Planning to take it all apart this afternoon and toss a meter on it to better know exactly what's happening.

All switch positions are affected equally.
The tone of the 300k pot would be brighter than the standard 250k volume pot, so the resistor was mitigating some of that increase. The pot I bought was a linear 300k sealed pot so I hope that's what was delivered. I'll check after work today.

The pick I have attached has the old 300k CTS pot which unfortunately had a bit longer aluminum shaft and I did not wire in the resistor. Shaving down the shaft broke one side of the cheap aluminum, so I had heard the Bourns sealed pots were better and had the proper sized "brass shaft". When it came I was happy with the quality of the product. Thanks!
 

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Odell

Strat-Talker
Mar 24, 2011
158
Nashville TN
I've got that resistor mod on my strat. It adds a little chime associated with Silver Sky guitars and wakes up the pickups a bit. I'm assuming the guitar worked with the CTS pot, right? How do you have the sealed pot wired? It looks the sealed pot has a plastic body. Since you can't solder your grounds to the back of the volume pot, how does that work? Do you need to add a ground wire somewhere?
 
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Lower_48

Strat-Talk Member
Nov 29, 2021
27
Midwest
I've got that resistor mod on my strat. It adds a little chime associated with Silver Sky guitars and wakes up the pickups a bit. I'm assuming the guitar worked with the CTS pot, right? How do you have the sealed pot wired? It looks the sealed pot has a plastic body. Since you can't solder your grounds to the back of the volume pot, how does that work? Do you need to add a ground wire somewhere?
Since this was a full build I didn't get a chance to test the CTS pot before I found the shaft was too long and decided to try my Dremmel to shave it down. (poof)

The plastic body pot has a grounding ring and pole to solder too. So the ring gets sandwiched to the pick guard shield and seems to do the job just fine. Here's photo of just the sealed pot, wired with the resistor. Lot's going on there. All of my grounds are attached to that grounding ring prong on the lower right.
 

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Lower_48

Strat-Talk Member
Nov 29, 2021
27
Midwest
Opened up the PG and removed the wires from the pot and measured values from 0- 299.5 without any drop outs at either end as I found when it was connected to the rest of the wiring. I'm new to meter work, and in the past have only used mine to check continuity.

Edit: Getting 25.49k out of the resistor
 
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CB91710

No GAS shortage here
Platinum Supporting Member
Feb 24, 2019
11,771
SoCal
Is there any specific reason you didn't use conventional CTS/Alpha/Bournes pots?
Curious where you heard that the sealed pots were "better"... and "better" in what way.
Conventional pots have been used without issue for decades.

Sometimes, items may be better for a specific/instrumentation/precision application, but they may be more sensitive to thermal and handling damage.
 

Lower_48

Strat-Talk Member
Nov 29, 2021
27
Midwest
Is there any specific reason you didn't use conventional CTS/Alpha/Bournes pots?
Curious where you heard that the sealed pots were "better"... and "better" in what way.
Conventional pots have been used without issue for decades.

Sometimes, items may be better for a specific/instrumentation/precision application, but they may be more sensitive to thermal and handling damage.
I heard that a sealed Bourne pot never oxidizes or get's dirty. So no worries about a scratchiness years down the road. Since I've replaced a few bad pots in my day I thought I'd give the sealed pot a go on my new build. Here's a video from Bourne that describes the differences between their pots and the other brands. The Bourne pot I purchased is made specifically for guitar applications, so it seems like a good choice. Given that it's a 300k pot that measures 299.5, that's pretty spot on to what I wanted.

Likely there's something in the wiring of that pot that caused the issue. Any thoughts on what?

Thanks again for your help!
 
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Lower_48

Strat-Talk Member
Nov 29, 2021
27
Midwest
The resistor looks right in your photo (orange, orange, green = 3.3 meg). You might try taking the resistor out of the circuit before measuring it.
I took everything off the volume pot and measured it and the resistor. Thanks for the double check! I'll put it all back together the same way according to the schematics unless anyone can tell me what might have caused the issue.
 

Stephen James

Strat-O-Master
Vendor Member
May 30, 2016
513
Iowa City
I took everything off the volume pot and measured it and the resistor. Thanks for the double check! I'll put it all back together the same way according to the schematics unless anyone can tell me what might have caused the issue.

Edit: Getting 25.49k out of the resistor

If you put a resistor that measures 3300kOhms (3.3MOhms) between input and ground, I feel your problem will go away..

Edit: If your reading is correct, it should be like you used a 24kOhm pot with all the action bunched up at the low volume end: signal would be the same volume (because of 25k across the input to ground), until reaching the rotation where the pot trace is below 25k to ground, then it would get quieter. But this isn't what was happening. At this point I would do what @CB91710 suggests below and try just the pot to see if you get expected results..
 
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CB91710

No GAS shortage here
Platinum Supporting Member
Feb 24, 2019
11,771
SoCal
For now, try it without the resistor and see if it's working.
Odd that a 3.3m resistor would drop to 25k.
 

Stephen James

Strat-O-Master
Vendor Member
May 30, 2016
513
Iowa City
Since this was a full build I didn't get a chance to test the CTS pot before I found the shaft was too long and decided to try my Dremmel to shave it down. (poof)

The plastic body pot has a grounding ring and pole to solder too. So the ring gets sandwiched to the pick guard shield and seems to do the job just fine. Here's photo of just the sealed pot, wired with the resistor. Lot's going on there. All of my grounds are attached to that grounding ring prong on the lower right.
What was the part/model number of the pot?
 

Wound_Up

You can call me Duane 😁
Jan 23, 2020
5,790
NW LA
If you attached all of your grounds to one of those 3 lugs on the potentiometer, I'd start with that. I've never grounded all of my grounds to the negative lug of the 3 lugs on a pot. Always the back.

Personally, I'd move all the grounds from that pot to the output jack ground lug and see what happens.
 

Lower_48

Strat-Talk Member
Nov 29, 2021
27
Midwest
If you attached all of your grounds to one of those 3 lugs on the potentiometer, I'd start with that. I've never grounded all of my grounds to the negative lug of the 3 lugs on a pot. Always the back.

Personally, I'd move all the grounds from that pot to the output jack ground lug and see what happens.
Good advice Thanks!
 

Scott Baxendale

Most Honored Senior Member
Silver Member
May 20, 2020
7,297
Sante Fe, NM
Well the build is coming along, and I've put everything together today only to find one head scratcher of a problem. I have a Freeway switch with independent tone controls and a Bourns sealed 300k volume pot with a 3.3m ohm resister across the hot and ground. After plugging it in and turning it up to 10 for tuning, I get no output. Knowing everything was wired according to the schematics, I started flipping switches and twisting knobs until I start seeing letters show up on the tuner. Good news! But then I find the problem is in my volume pot. Turning the volume all the way up or all the way down cuts off the power completely. Seems like a bad pot but I just wanted to run it by this group of experts to hear your thoughts. This is the first time I've used a 300k pot for volume with a resistor, and even though it's connected per the schematics I have no idea what it's supposed to accomplish except possibly drop the pots value to 274k and possibly brighten the tone a bit. Thoughts on why this volume pot drops out before it hits its stops on either end?

I've attached the wiring for the volume pot. The freeway with seems to be working properly so no need to add to the confusion.

Thanks and a bag of chips!
The third far right lug, needs to go to ground.
 

Nick L Plate

Strat-O-Master
Sep 15, 2020
549
Santa Barbara
These are not the droids you are looking for. A setup this complicated seems ill-advised from the get-go other than as an "is it possible?" challenge. I can't imagine trying to occupy a musical headspace, playing, with all those switching options. Speaking only for myself as a player, of course.
 


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