PCB layout and components help w/ files now.

hey guys,
I just thought I should ask this here..

I'm doing my first attempt in pcb design. I'm using expresspcb for this.

and here is the schem, (I found this on the web a while ago) or this distortion box that I wanted to attempt.

www.geocities.com/CollegePark/Library/1355/hotbox.jpg

My questions are about the caps on this circuitry:

1 - the author describes that all caps should be 600V, unless its otherwise stated. So, what about the caps after pin 8 of the V1? .022u and 50 pF. I thought they could be at 50V or so.

2 - I'm also having trouble locating polirized and non-polarized for these. I only find the non-polirized

whe I finish the design, I'll post it so everyone can criticize it.
thanks guys
Gil

Make them non-polarised at not less than 300V rating. If you were to get a fault on the first half of V1 so no current flows through it, you could end up with almost the full HT voltage across the cathode resistor of the second half. This has to be stood off by the caps in the tone control.

> 50 pF. I thought they could be at 50V or so.

The 50pFd treble cap has full cathode voltage on it: ~150V, but as Boswell says it could be full supply voltage at start-up or in a fault. So at least 255V, which means 250V and cross ALL your fingers, or 400V. The HV cap market is thin: you may wind up 600V.

BUT: 50pFd is so very small, that you probably won't find any "low" voltage versions. Historically, good 50pFd caps are Mica, and they don't bother to shave little 50pFd specks of mica thinner than 500V.

I do not know why the 0.1uFd cathode caps have polarity marks. At 0.1uFd, you will probably use paper/plastic film caps, which don't really have polarity. You may find some teeny 0.1uFd electrolytics, and 5V would be plenty here; but 0.1uFd 5V electrolytic would be too small to see.

The polarity marks are handy if you decide you want more bass. 0.1uFd bypass is a screamer; you want ballz, use 5uFd-25uFd. At this size, you use >5V electrolytic, and you must observe polarity.

> attempt in pcb design

IMHO: nail the sockets and pots and jacks onto a box, you can hand-wire it 10 times faster than you can make a PCB. You can "nail" the power supply caps with silcone caulk or ShooGoo, and then all the power supply can be wired on cap leads. Not elegant, but works.

thanks for the response guys,
I'll just use 600V all around than, except where noted.

As far as hand wiring.. I thought about that, but this project is to just take a shot at pcb design.

Like I mentioned before, I'm using expresspcb and I'll post results later.

thanks again guys..
Gil

Alright guys,
so here it is..
Please take into consideration this is my first attempt at this kind of stuff.

let me know if there is something terribly wrong.
www.braudio.com/forumfiles/hotboxattempt1.bmp

here is the pcb file

www.braudio.com/forumfiles/hotboxattempt1.pcb

I just realized that the bmp export doesn't show the traces... duh..
I think I'm going to have to do a screen capture.

Thanks
Gil