Author Topic: Kay Fuzztone and PT80 build - hum  (Read 2277 times)

finetuned

Kay Fuzztone and PT80 build - hum
« on: March 01, 2007, 11:20:37 AM »
Hi,

I've just built two effects: A PT80 (GGG), and a Fuzztone (uStomp.com).
The problem with both, is that they produce a hum. The PT80 only does this when the power is on, which leads me to believe it might be one of the ICs?

On the Fuzztone, it is there even when the power is off. The hum gets louder if I connect my expression pedal to the stereo jack. (I wired it up for an external expression pedal, as opposed to wiring the pot to the board). These connections have been checked and double-checked. This leads me to believe that there might be an error in the schematic? The signal line that goes to the output jack is connected to the middle lug of the pot in the expression pedal. Is this right?
BTW: the pot in the expression pedal is only 20k, as opposed to the 50k in the schematic. The effect does work, it's just that there's hum.

What could cause this hum?
I've soldered them to perfboards.
It's not my PSU. It's a new, stabilized PSU which (proven by the Kay Fuzztone) does not cause the hum. My old, unstabilised PSU does increase the hum in the fuzztone, on testing.

I hope someone can point me in the right direction with this?

Thanks a lot.

PS: I used BC459B transistors in the Fuzztone. I couldn't find the pinout of the originals anywhere, can anyone inform me if they are the same?

finetuned

Re: Kay Fuzztone and PT80 build - hum
« Reply #1 on: March 01, 2007, 11:31:52 AM »
Eh, I mean BC549B of course.... sorry....

puretube

Re: Kay Fuzztone and PT80 build - hum
« Reply #2 on: March 01, 2007, 12:59:54 PM »
very probable it`s a ground-wiring mismatch (loop);
surely someone will soon chime in and help...

finetuned

Re: Kay Fuzztone and PT80 build - hum
« Reply #3 on: March 03, 2007, 03:58:20 AM »
Can anyone help me on this one?
I've checked, and every connection to ground is correct. I just can't find the problem in here, I'd be glad if anyone could help me out...

thanks

finetuned

Re: Kay Fuzztone and PT80 build - hum
« Reply #4 on: March 03, 2007, 04:23:13 AM »
If I connect the input of the fuzztone to the input of my amp, there's very little hum. If I connect the output of the fuzztone to the amp, there's lot of hum. Has anyone else successfully built the Kay Fuzztone according to the uStomp.com wiring diagram? I know the schematic was updated a few times, but was the wiring diagram also?

g3rmanium

Re: Kay Fuzztone and PT80 build - hum
« Reply #5 on: March 03, 2007, 07:36:16 AM »
PS: I used BC459B transistors in the Fuzztone. I couldn't find the pinout of the originals anywhere, can anyone inform me if they are the same?

The transistors in my Kay Fuzztone are marked C945 TQ237.

There have been doubts about the schematic and I have proposed to draw one from my pedal -- which I still haven't done so far. :icon_redface:
Call me Johann.

finetuned

Re: Kay Fuzztone and PT80 build - hum
« Reply #6 on: March 03, 2007, 07:52:13 AM »
I fixed it. Looking at the shematic of the Fuzztone, and to the datasheets of the BC549B, it turned out that the pinout of the transistors were different.

The hum was also almost gone when I pulled Q3. Thissounds better (?!) than orienting them in the correct way.
So I now use it with just Q1, Q2 and Q4 (on this moment, all BC549B, I might experiment with different transistors), but all three have the collector and emitter reversed from the way they are in the shematic.

Weird.

Stan.

ustompsteve

Re: Kay Fuzztone and PT80 build - hum
« Reply #7 on: March 04, 2007, 10:09:37 AM »
I have built a Kay Fuzz using the uStomp layout and it works.

I record with it a lot. It is a very sweet box.

There is a bad schematic floating around. I have the corrected one on my web site. Spaceshot verified it from a real unit. I think there is a discussion in the archives.

--steve