Gain pot values question ?

[MartyMart]

Just picked up a "Daphon" heavy metal pedal quite cheaply, its one of the nice "metal cased" series and is built like a tank ( weighs nearly as much!)
The tone/drive is great but the drive pot is like a digital switch: on or off !
there's NO change as you increase the level on the 250k drive pot.

I dont have a schem, and its quite packed in there, but am i correct in thinking that an increase in pot value would give me a better range, ie; i'd like to be able to "clean up" the signal at lower pot values and still get full drive at higher settings? ( 500k-1meg )
Or, do i have to dive into the board a bit more to make some adjustments to the gain stages pre- drive pot ??

Thanks in advance for any ideas,
Marty.

[dolhop]

I'd have to see the schematic in order to say how to best change the gain stage.  However, if you're getting a binary response, then most likely you have a bad pot and swapping it out with the same value would make it work properly again.

[MartyMart]

Thanks Dolhop,
yeah i'm thinking "bad pot' too, as it can't have been designed to stay at one value, just can't find a schem anywhere and these "metal series" are not on Daphons web site at all ! wierd !
Guess i'll hunt down a 16mm 250k log from somewhere and give that a go.
Cheers,
Marty.

[dolhop]

If you have a multimeter, measure the resistance between terminals 1 and two as you slowly turn the pot from one end to the other and you should see it gradually change value.  Do the same for terminals 2 and 3.  Of course, all with the power disconnected (no battery).  If they do gradually change, then the pot is okay and you have some other problem.  If it goes from 0 to 250k instantly at some point, then it's a bad pot.  Remove it using a solder sucker.  Test the resistances again to make sure it's the pot and not something in the circuit.  

The pots they use in effects are hard to come by.  If you can fit a standard pot in there, you can dremel cut the post to be shorter.

[MartyMart]

Thanks again !
The pot jumps to almost 250 at 10% of travel, so its screwed !
Found a 16mm pot for about 1 dollar 50, which will fit fine.
The only problem is the original "post" on the pot is "fluted" to grip the knob, and the new one is smooth, so we'll see !!
Cheers,
Marty.