Proco Rat Layout help

[silentmike]

Hi there, today I've been building my brother a rat for Christmas working off this diagram:

http://www.aronnelson.com/gallery/main.php/v/cathexis/Veroboard+Layouts/ProCo+RAT/ProCo+RAT.JPG.html

Everything was going smoothly till I noticed that there's no marks for polarity on the electrolytic caps. Does anyone know which way round they're meant to go?

Cheers!

[ibodog]

If you look closely at the electro's you'll see that one side is shaded a bit darker.  That is the negative side.  In the layout you linked it looks like they're all pointed down.

[silentmike]

Ahhh, cheers for that. I didn't notice the shading on the diagram!

[Processaurus]

That seems to happen a lot, with different DIY layouts, boards, etc that are out there, remember the + side of electrolytics want to go to the side with a higher voltage present on it, an easy one to figure out without any schematic is if one side is tied to ground (and it is a negative ground circuit, like 95% of all out there), that will be the negative side.

Another easy one with pedals is on an output, the + goes toward the circuit output and the (-) goes toward the volume control/output jack.

[silentmike]

Cheers, I will bear that in mind.

Now I've got a new problem. My true bypass is working fine (the signal goes in and of the footswitch fine), but when I turn the pedal on I get no signal coming into the pedal. When poking around with an audio probe, you can hear that there is no signal. Could it just be a faulty footswitch? Or is there probably something more sinister at work?

All the grounds are fine and the tip of the jack isn't grounding when I plug the cable in either. I've triple and quadruple checked the solder joints and breaks and tried using a different transistor. I'm using a power supply that's sending out a steady 8.9V too.

[R.G.]

Could it just be a faulty footswitch?

Yes, it could.

Or is there probably something more sinister at work?

Only possibly, not probably.

This is one of those instances where one test with a multimeter will get you more real information than two hours on the internet. 

[silentmike]

Right. I've changed the footswitch (I had a 4pdt lying around) that changed nothing and I have checked the original switch which appears to be fine. So I went and took everything off the stripboard, rebuilt it and it still doesn't want to work. I'm using holders for the ic and transistor so they shouldn't be fried. I was wondering how easy it was to fry diodes? It's possible that i may have overheated them while removing from the board or checking the solder joints...

[Renegadrian]

That layout is more then verified, by the author and by myself!
I usually try the circuit with "flying wires" if I am not sure about it working properly. just in and out and battery.
Also, RAT and similar circuits with IC and that diodes configuration should work even with burnt diodes or no diodes at all...
Try to disconnect them, but I guess it's not them...

[silentmike]

Ok, well now I've identified why I wasn't registering any sound at all. I had accidentally swapped out R7 for R8. So I had a 1M resistor where there should have been a 47 Ohm one and when poking round with the audio probe I can hear stuff coming in to pin 3 of the ic. Unfortunately nothing coming in pin 2 or going out though. Any ideas?

[silentmike]

I need a Christmas miracle here! I've replaced the diodes using the crocodile clip on my audio probe as a heatsink, and it has changed nothing. Here's my voltages:

IC:
    1 - 8.31
    2 - 7.85
    3 - 7.25
    4 - 0.0
    5 - 0.0
    6 - 0.60
    7 - 8.35
    8 - 0.0

Transistor:
    1 - 0.0
    2 - 1.83
    3 - 8.88

Does anything look odd?

[Vendt]

Hi,
I'm highjacking this topic this topic 'cause I've got a question about this layout. Didn't want to start a new topic 'cause it 's about the same layout.

http://www.aronnelson.com/gallery/main.php/v/cathexis/Veroboard+Layouts/ProCo+RAT/ProCo+RAT.JPG.html

Ok here for the question:

Why is there a trace-cut on D16?
The IC's Pole (D15) is connected to the transistor D19 via  jumpers A14-D14 and A23-D23. It looks to me as if the trisect is unnecessary.

Maybe there is a logical explanation for this...please let me know.

Thanx

[Renegadrian]

You see that the top row is dedicated to V, after it goes thru r7 - so one jumper should stay, I guess it would be the same if you omit that trace cut and that jumper, as long as the IC pin and the transistor gets voltage.

[Vendt]

That's what I thought...Thanx for the reply