Help With Component I.d. Please

[unclej]

i've got a couple of things i need help with please. one is just out of curiosity and the other necessity. one of the pictures here shows a small round component in a stomp box designed by a buddy of mine. the center is open and the white plastic ring in the center moves. what is it please?

the other question has to do with an original gibson maestro fuzz-tone. when i play through it with the effect off the volume is fine. when i engage the effect the volume reduces by approximately half. one of the resistors shows a negative reading with the probes held one way and no reading at all when reversed. i'm assuming that it's bad but the color codes on these only have three rings. the colors on the one that seems to be bad are yellow/gray/yellow. so could the bad resistor cause the reduction in volume and if so, what's the rating?

also, does anyone have or have a link to a schematic for the fuzz-tone. the only one that i found googleing was small and blurry.

as alway, thanks.

http://www.villagephotos.com/pubbrowse.asp?folder_id=1111428

[lovekraft]

...one of the pictures here shows a small round component in a stomp box designed by a buddy of mine.  the center is open and the white plastic ring in the center moves.  what is it please?...

It's a trimmer potentiometer - it works like a normal pot, but it's designed to be set to a fixed position, usually for calibration or level adjustment.

...one of the resistors shows a negative reading with the probes held one way and no reading at all when reversed.  i'm assuming that it's bad but the color codes on these only have three rings.  the colors on the one that seems to be bad are yellow/gray/yellow.  so could the bad resistor cause the reduction in volume and if so, what's the rating?...also, does anyone have or have a link to a schematic for the fuzz-tone.  the only one that i found googleing was small and blurry.

You cannot accurately check resistors unless you remove them from the circuit, so your measurements are irrelevant. For the record, that resistor has yellow-violet-yellow banding, making it 470 kilohm, and since it doesn't have a tolerance (4th) band, it's 20%. Bookmark this page for an easy way to decipher the color codes:

Resistor Color Code Calculator

The schematic is here:Maestro Fuzz-tone (courtesy of Pat Jankowiak )

If you have trouble reading it, pop it into any graphics software and scale it up about 150% - it won't fit on most screens, but you can read it with no trouble. Good luck troubleshooting it - GEOFex and Aron's Stompbox Page both have help on debugging circuits if you need it. HTH

[JohnnyG]

looks like lovekrafts sorted everything out. that fuzztone looks to be an interesting little circuit. i may have to have a play

[unclej]

lovekraft, as usual your information is invaluable and i really appreciate it. i found a color code but it didn't say anything about resistors without the fourth ring.

i had actually found the geofex site but not aaron's stomp box. looks very informative. again, thanks.

johnnyg, it's actually pretty cool sounding even at the loss of volume and my understanding is that it's one of the original fuzz boxes and was used in some pretty famous recordings.

[JohnnyG]

yeah like it says on the shcem lovekraft posted its supposedlly responsible for the fuzz from satisfaction. only problem is that it looks to be a fair bit of wiring and atm all i can build stuff on is perfaboard which is really not fun.

with regards tothe loss of volume i wouldnt have thought that would occour. id check the transistor in there that they're using as a squelch control and maybe play with the biasing voltage on it