Superb Boss FV500H mod

[Jacew]

I really like the construction of this volume pedal. Never really liked the taper however. Feels very clumsy compared to EB jr.

I've been trying to get used to it. But decided it's not working.

Not wanting to go switching pedals to no end I looked for replacement pot. Which turned out to be useless. Despite being cheap Alpha, there is no available replacements anywhere.

So I looked to replace wafer. Except that due to the construction of the lever, that alpha has half shorter slider any normal pot so that didn't work either.

So I replaced the exp wafer of the dual gang pot with 500k alpha with fullsize slider. And crosswired it's input and output lugs with orginal wafer.



Result was stunnigly good. As the second wafer in parallel now smoothens out the taper, it feels just as good as that EB jr. did. Without any of it's drawbacks...

 

[Alkerion]

Re: Superb Boss FV500H mod

Hi !

Could we have a bit more detail regarding the pot used (reference) and the wiring ?

Which pot did you change?

The volume dual pot is a 250k/500k, do you change it for a 500k/500k?
Or did you change the min volume pot we can adjust from outside ?

Thanks
Regards

 

[Jacew]

Re: Superb Boss FV500H mod

I didn't change the pot. Pot in Boss FV-500h is 25k/250k dual gang and has only 1/3 rotation of normal. I couldn't find replacement anywhere. If anyone knows where to find one I'd really like to know!

What I did was that I opened the pot and changed the slider part inside the pot to 500k. Then I wired it backwards in parallel with the other wafer, so the pedal acts less quickly when lowering volume.

 

[Alkerion]

Re: Superb Boss FV500H mod

Hi !
Sorry, I was wrong, mine is 10k for Exp and 250k for Vol, it's written on it...
When you write : "Then I wired it backwards in parallel with the other wafer", does it mean that you wired the Vol pot with Exp pot ?
How did you change it ? (I?ve opened it and it seems quite hard to remove the wafer without damaging anything)
You bought a new dual 500k pot ?
Linear, audio or log?
Can you still use Exp ?

To me the volume curve on this pedal is not good, the volume change too quickly in a too short foot amplitude, I would like to improve that.
BR

 

[Jacew]

Re: Superb Boss FV500H mod

Hi !
Sorry, I was wrong, mine is 10k for Exp and 250k for Vol, it's written on it...
When you write : "Then I wired it backwards in parallel with the other wafer", does it mean that you wired the Vol pot with Exp pot ?
How did you change it ? (I?ve opened it and it seems quite hard to remove the wafer without damaging anything)
You bought a new dual 500k pot ?
Linear, audio or log?
Can you still use Exp ?

To me the volume curve on this pedal is not good, the volume change too quickly in a too short foot amplitude, I would like to improve that.
BR

Yep, exp side is 10k. My bad.

I just used 500k pot wafer I had lying around. It's changeable. You bend the 4 tabs that hold the existing wafer and it should drop right out. Then put in other and bend tabs back to hold it in place.

I need to open it up to make sure as I don't fully remember which lug I connected with which, but basically I wired the exp side of the pot parallel with volume side.

Obviously it won't be usable as exp pedal after that.

 

[Alkerion]

Re: Superb Boss FV500H mod

I've opened my pot, but to replace the 250k wafer I've to remove the axis, something that will for sure damage the pot.

So you've replaced the 10k or the 250k ?

Why haven't you just replaced the dual pot by a single 500k ?

On my setup the volume is OFF at 160K, above 160 it's useless, and I can't ear any differences on high volume from 50K to 0. the usable range is quite poor.

I'll first try to replace the pot by a good 250k.

 

[Alkerion]

Re: Superb Boss FV500H mod

Something strange is that when the pedal is set to highest volume the Vol pot value is 2.7K, do you have the same value ?

I've ordered B250K and B500K to test.

I'll also remove the circuit boards and wire directly, and add a switch to select the impedance 250K, 100K and 25K an the volume pot.

I'll post a few pictures and keep you informed once done.

 

[Jacew]

Re: Superb Boss FV500H mod

Something strange is that when the pedal is set to highest volume the Vol pot value is 2.7K, do you have the same value ?

I've ordered B250K and B500K to test.

I'll also remove the circuit boards and wire directly, and add a switch to select the impedance 250K, 100K and 25K an the volume pot.

I'll post a few pictures and keep you informed once done.

I don't remember if it went all the way to 0, but it should and I recall it does. I'll check that too. If it doesn't it may have worn out or misaligned pot.

Those pots you've ordered are not going to work. I said it multiple times in this thread that pot in Boss FV-500 has unique rotation: It only rotates 1/3 of usual lenght so you need special pot for it.

EDIT: Unless you were going to gut that for the mod I mean...

 

[Alkerion]

Re: Superb Boss FV500H mod

I've modified a B250K pot to be a D shaft :


Then, wired it directly to the jacks the simplest way :


The feeling is way better than the original pedal, the only "issue" is that I still have a little volume when the pedal is down, it will probably be much better with the 500k pot.

To follow....

 

[Jacew]

Re: Superb Boss FV500H mod

The feeling is way better than the original pedal, the only "issue" is that I still have a little volume when the pedal is down, it will probably be much better with the 500k pot.

To follow....

I'm sure of that. They're nice if they just had better electronins inside. Nice to see others improving them as well.

You have volume when pedal is heel down because regular pot won't rotate to 0 due to the construction of the pedal. It also won't turn fully open. 500k or 250k won't change that.

Did you measure the load when fully open. I'd be interested to hear what you get?

 

[Alkerion]

Re: Superb Boss FV500H mod

Original pot : 237K -> 2K7

New B250K pot: 215K -> 16K2

I've my idea to solve these issues, already worked on it and obtained 190K -> 2R

I'll receive ma 500K pot in ~10 days, so I expect to have something around 400K -> 0R, and with a 600K resistor I'll reduce the 400K to around 240K, that way I'll have a 240K -> 0R perfect pot

Will also add a switch to set the min volume to other values than 240K (I'll try 100K & 25K).

With high quality jack socket and minimum wiring the tone will be back and I'll have less interference, all that with perfect feeling under the foot to adjust the volume.

 

[Alkerion]

Re: Superb Boss FV500H mod

For those interested, here is my "schema" :


and first rewiring (original connections but min vol pot on VOL not connected):

 

[Jacew]

Re: Superb Boss FV500H mod

Original pot : 237K -> 2K7

New B250K pot: 215K -> 16K2

I've my idea to solve these issues, already worked on it and obtained 190K -> 2R

I'll receive ma 500K pot in ~10 days, so I expect to have something around 400K -> 0R, and with a 600K resistor I'll reduce the 400K to around 240K, that way I'll have a 240K -> 0R perfect pot

Will also add a switch to set the min volume to other values than 240K (I'll try 100K & 25K).

With high quality jack socket and minimum wiring the tone will be back and I'll have less interference, all that with perfect feeling under the foot to adjust the volume.

How do you plan to get that 16k to 0 at heel down? I couldn't figure that out and would certainly be interested if it is possible.

Just heads up that you won't waste your time...

 

[Alkerion]

Re: Superb Boss FV500H mod

No rocket science, just a little hole :

 

[Jacew]

Re: Superb Boss FV500H mod

I meant how we're you planning to get the pedal all the way silent: You get sound because theres 16k load (as your measurements show) even when it should be silent. Also you don't get full output through pedal at the other end for same reason.

I don't know a way to fix that electrically. That's why I couldn't just replace the pot (and used the second wafer in parallel). Stock one has shorter rotation than any aftermarket pot.

EDIT: Well, I didn't quite got your previous post first. Sure moving the pot to close fully fixes that issue. But then your volume is not going fully open... Whether it's 250k or 500k doesn't really affect that.

 

[Alkerion]

Re: Superb Boss FV500H mod

I could be wrong, but for me the volume is maximal when the resistance is equals to 0R.

At the opposite, the highest the resistance is, the lower the volume is.

The guitar should be dead silent at around 240K.


If you've linked in parallel your 500K and 250K pots you must have a 160K pot, so it mustn't be silent at all.

If you've linked in serial your pots you must have a 750K pot, too silent too early, probably the same with a 500K pot


Measure your min/max values and we will see what you have exactly, and let us know how you've wired all that.

what makes you think it's a 1/3 rotation pot ?

which pot did you buy (A, B or C) and where ?

The pot in Boss FV500H is a linear one (B250K), the log curve is mechanically created with the 3 axis mechanism.

 

[Jacew]

Re: Superb Boss FV500H mod

I could be wrong, but for me the volume is maximal when the resistance is equals to 0R.

At the opposite, the highest the resistance is, the lower the volume is.

The guitar should be dead silent at around 240K.

There is two resistances you need to measure to determine how much signal the pedal gets through and how much it loses. Volume depends of the relation of those two:

Signal to ground: This is what you've been measuring and modifiying. You're correctly calculated how to get this right. When it's 0 at heel down you'll always have silence. Higher this is doesn't practically affect the volume though, it does have some effect of tonal transparency and such though.

Input to output: This you measure between input + and output +. When this is zero, signal passes through. Transparency depends of the load (eg. Signal to ground resistance). If resistance between input and output + is not 0, you lose volume, which happens when pot is not fully open.

When you move the pot silent, input to output resistance rises and signal to ground drops. Vice versa when you move the pot louder.

If you've linked in parallel your 500K and 250K pots you must have a 160K pot, so it mustn't be silent at all.

If you've linked in serial your pots you must have a 750K pot, too silent too early, probably the same with a 500K pot


Measure your min/max values and we will see what you have exactly, and let us know how you've wired all that.

I wired it parallel between input and output lugs, not ground. So it doesn't affect the load of the pedal. Only taper curve.

I did measure my pedal:
Toe down signal to ground is 222k, input to output is 0. So full output.
Heel down signal to ground is 0, input to output 100k (This would normally read 222k. It doesn't because I have that 500k wafer wired in parallel)

what makes you think it's a 1/3 rotation pot ?

I opened it up. The resistive carbon strip inside is only 1/3 lenght of that you have in normal pot. Rest of circle is fully conductive.

which pot did you buy (A, B or C) and where ?

I did not bought a new pot! I opened the old pot. When you open it the 25k side of it drops right out. I then put part gutted from 500k Alpha in place of it. I thought I said this already couple of times...:34:

The pot in Boss FV500H is a linear one (B250K), the log curve is mechanically created with the 3 axis mechanism.

That's right. Good thing to point out.

 

[Alkerion]

Re: Superb Boss FV500H mod

OK, thanks for the details, I was half right.


I start to understand why you keep the original 250k pot.


So you wired that way ?




I've opened it, here is the 10K one :


Values I have :

Original pot:

Max Vol
1-2 : 4.4K
2-3 : 222K

Min Vol
1-2 : 226K
2-3 : 1R

Standard B250K pot:

Max Vol
1-2 : 14K
2-3 : 220K

Min Vol
1-2 : 215K
2-3 : 22K

Standard B250K pot in new hole :

Max Vol
1-2 : 2R
2-3 : 233K

Min Vol
1-2 : 185K
2-3 : 47K


I'll wait the 500K and wire like you to test if it suit my need.

 

[Jacew]

Re: Superb Boss FV500H mod

OK, thanks for the details, I was half right.


I start to understand why you keep the original 250k pot.


So you wired that way ?

View attachment 95472


I've opened it, here is the 10K one :
View attachment 95474

Values I have :

Original pot:

Max Vol
1-2 : 4.4K
2-3 : 222K

Min Vol
1-2 : 226K
2-3 : 1R

Standard B250K pot:

Max Vol
1-2 : 14K
2-3 : 220K

Min Vol
1-2 : 215K
2-3 : 22K

Standard B250K pot in new hole :

Max Vol
1-2 : 2R
2-3 : 233K

Min Vol
1-2 : 185K
2-3 : 47K


I'll wait the 500K and wire like you to test if it suit my need.

Values you put there show clearly the problem:
For Min Vol (silence) you should have 0 between 2-3 (like original pot has) and for Max Vol you should have 0 between 1-2. (I guess there might have been issue with pedal not fully clockwise, misaligned pot, or dirty pot, since original had 4k).

I wired 250k parallel to tabs 2-3 of 500k. Close to zero it won't make big difference anyway, so it's more effective when it acts backwards.

10k wafer drops out when you bend the tabs back of the pot, without need to take it apart. So you can put it back together. It seems I remembered 1/3 wrong. That's actually 1/2 lenght of usual strip.

 

[Alkerion]

Re: Superb Boss FV500H mod

Hi!

I'm sorry but still not crystal clear how you wire all that.

You wrote :

A) "I wired it parallel between input and output lugs, not ground."

B) "I wired 250k parallel to tabs 2-3 of 500k"

For me 1 is Input, 2 is Output and 3 is Ground.

Could you please draw a little schema ?

Thanks