Superb Boss FV500H mod

[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...

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 ?

[ATTACH=CONFIG]95472[/ATTACH]


I've opened it, here is the 10K one :
[ATTACH=CONFIG]95474[/ATTACH]

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

[Jacew]

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

500K is not connected to ground. Just move red and yellow connections of 500k from 1 and 2 to lugs 2 and 3 in that scheme you posted.