Fetzer Ruby; some pictures and a question

[Krinor]

Hey all,

Below are some pictures of my latest build, the Fetzer Ruby.
I built it on a vero board, and I've promised myself that this is the last project I will build on that kind of board! I spent hours searching for shorting sources and small cracks in the copper. Next time I'll solder the whole thing point to point or even in mid air  .
I'm experiencing some strange behaviour from the volume pot which is an 100k audio taper. When I turn it sound comes suddenly at about 80 or 90 k and then nothing happens untill it's at 50 or 60k where there is a slight increase in volume. Turning it fully clockwise it suddenly cuts out at about 400 ohm. There is also some scraching noise when the pot is turned. I've tested it thoroughly with my DMM and in terms of ohm readings it performs flawlessly. What might be wrong ? Could it have anything to do with some leakage somewhere else in the circuit ?



The amp opens like a drawer. It's locked underneath with a little screw which passes through the wood and into the chassis. I'm running it from a wallwart at the moment, but will put a battery connector in it later.



Below is a gutshot. I didn't have a trimpot at hand so I just experimented with different resistors on long wires untill I came close to 4,5V for the Jfet drain. My current reading is 4,86V. I hope this is acceptable ?
(There is also an unused stereojack which eventually will become a headphones output.)



Thanks for browsing.

-Kristian

[Harry]

Very nice job! Where'd you get the enclosure?

[Krinor]

The oaksides are made from a shelf. The steelchassis is cut from something I found at work (I work in the construction buisness). The steel is quite thick, so boring the holes is timeconsuming, but the result is pretty nice.

[Harry]

Well since no one has replied yet. Is the pot new or old? Check solder connections to make sure they're solid to avoid scratchy sounds. Also if the knob is to tight against the metal surface it might be the cause of the scratchy noise. Otherwise I'm unfamiliar with the circuit and would probably assume a different value/taper may fix things.

[km-r]

it sounds like a scratchy old pot... dmms sometimes take readings too fast...
why not try replacing the pot?

the amp looks nice and neat dude!

[Krinor]

The pot is brand new. That's why I didn't imediately replace it. I'll try that this afternoon though.

[the_random_hero]

The pot is brand new. That's why I didn't imediately replace it. I'll try that this afternoon though.

I had pots that were brand new and did exactly what you describe. I ditched that supplier and started using Alpha pots - I haven't had a problem with them since.

[Mandrake754]

I had pots that were brand new and did exactly what you describe. I ditched that supplier and started using Alpha pots - I haven't had a problem with them since.

from the pictures, he is using alpha pots... not that it means that's not the problem... just thought i'd point it out.

[the_random_hero]

I had pots that were brand new and did exactly what you describe. I ditched that supplier and started using Alpha pots - I haven't had a problem with them since.

from the pictures, he is using alpha pots... not that it means that's not the problem... just thought i'd point it out.

Well there you go, I should be more observant in the future 

[Krinor]

Yes I have Alpha pots in there. I changed the volume pot today. It didn't make a difference. It's still scratchy and doesn't perform like it should. I have even changed the Jfet. I suspect there must be some seriously bad soldering somewhere. But vero boards are so cramped that it's almost impossible not to make a mistake IMO. I guess I'll just have to start over with something more suitable to solder on.

[ambulancevoice]

yeah, im not much of a fan of vero boards
every circuit ive built on one has not worked, except my bazz fuss with sorta works
use a perf board man