ProCo Rat Clone Troubleshooting... Please help!

[stringsthings]

You lot are the greatest!

So, using an audio probe I found that the tone pot wasn't working, switched it with another and then found the volume pot wasn't working either. Once I switched the volume pot with another the effect was working apart from the tone pot not having any effect on the sound whatsoever... What could be the problem here?

Thanks again. I'm learning loads and making real progress it seems!

Thank you very much! 

Glad you got it 90% working.  Learning while troubleshooting is very rewarding, IMO.  You are making significant progress.
Audio probes are super useful.  The next time you need to troubleshoot, the process will be smoother.  It's all part of pedal DIY.

2) Link is not connected properly (effectively there is no link)
3) Pot wiper is not making contact with the track (broken pot, or potentially bad solder joint on middle lug of pot)
4) C8 is not connected properly. This could be at either the top or bottom of the cap - either would lead to the filter having no effect.

I concur with the Druid here.  Using your continuity beeper on your DMM, double-check that C8 is grounded on one end, and connected to the tone pot wiper on the other end.
If that's good, visually verify the value of C8.  If that's good, make sure your tone pot wiper is connected to the outside lug.  You may want to test out your pots before wiring them
into the circuit since you've found 2 bad ones.  That's a bit unusual.  Pots are normally pretty hardy things.

[intripped]

Pots are normally pretty hardy things.

i've experienced many faults with pots, i think due to too much heat applied while soldering.
the metal pins could loose proper conection with the carbon trace inside the pot (metal pins are mechanically crimped on a fiber disc, that carries the carbon trace)

i'm talking of the most-used Alpha-16mm-type potentiometers.

before soldering, i usually test a potentiometer with the multimeter:
in ohm-reading mode, i read the value between pins 1 and 2, and then between pins 2 and 3.
while reading the value, i usually also apply a slight pression on the pot's pins, trying to move them up-down, right-left.
if the read value is steady, than the pins are making good connection with the carbon trace.
if instead i notice unexpected changes in the reading on the multimeter, then probably i have a bad pot.

if so, then i try to crimp again the metal pins, with the help of a pair of pliers; but i warn you:this is a difficult and delicate operation, and it's very easy to apply too much pressure and break the fiber disc. if this happens the pot is definitely trashable.

[jimladladlooklike]

So I had originally connected lugs 2+3 of the tone pot with a jumper (just a piece of component wire I had spare) as the schem suggested. Once I removed the jumper the tone pot worked just fine. Issue solved!

Little concerned about the dodgy pots though. perhaps I applied too much heat and damaged the internal wiper part?

But I seem to be having yet another issue. It's nothing major but when there is no guitar plugged into the pedal and the pedal is on and signal going to an amp I get some weird sounds coming from the pedal... (is this what's known as oscillation?) the pitch of which can be controlled with the pots. Doesn't happen when the guitar is connected so not a huge issue but none of my real pedals do this.

Also, I have a Westone Thunder with the loudest pickups ever. So so loud. The pedal doesn't seem to like this. When The gain isn't on full you sort of lose the front end of each note/chord, especially on lower strings...

Cheers again!

[stringsthings]

So I had originally connected lugs 2+3 of the tone pot with a jumper (just a piece of component wire I had spare) as the schem suggested. Once I removed the jumper the tone pot worked just fine. Issue solved!

Little concerned about the dodgy pots though. perhaps I applied too much heat and damaged the internal wiper part?

But I seem to be having yet another issue. It's nothing major but when there is no guitar plugged into the pedal and the pedal is on and signal going to an amp I get some weird sounds coming from the pedal... (is this what's known as oscillation?) the pitch of which can be controlled with the pots. Doesn't happen when the guitar is connected so not a huge issue but none of my real pedals do this.

If you removed the jumper between 2-3, and the wiper isn't connected anymore, then your pot is damaged.
Excess heat could be the culprit.  Lug 2 is the wiper.

If the noise is high-pitched and it increases as you turn the gain up, that's oscillation.  Putting the build into the enclosure ( if you haven't already done so )
will likely help.  Also, for high gain circuits, lead dressing is important.  Keep all input and output wires as short as possible and as far away from each other as possible.
For extreme cases of oscillation, shielded wire is an option, but you shouldn't have to do that for a Rat.  I've built several Rat's and haven't had any oscillation probs.

You can lower your pups if they're too hot.

[ElectricDruid]

So I had originally connected lugs 2+3 of the tone pot with a jumper (just a piece of component wire I had spare) as the schem suggested. Once I removed the jumper the tone pot worked just fine. Issue solved!

If you removed the jumper between 2-3, and the wiper isn't connected anymore, then your pot is damaged.
Excess heat could be the culprit.  Lug 2 is the wiper.

No, he said the tone pot worked fine, so there's no problem with the wiper and the pot can't be damaged.

[ElectricDruid]

But I seem to be having yet another issue. It's nothing major but when there is no guitar plugged into the pedal and the pedal is on and signal going to an amp I get some weird sounds coming from the pedal... (is this what's known as oscillation?) the pitch of which can be controlled with the pots. Doesn't happen when the guitar is connected so not a huge issue but none of my real pedals do this.

It sounds like the input is floating when there's nothing plugged in. R1 *should* pull the input to ground if there's nothing in the jack, so perhaps it's not soldered correctly?

Not sure. Could be quite a few things in a pedal with decent gain. Try cleaning the board, for example. I've sometimes been able to solve similar things just by getting rid of muck in the gaps between the strips on a stripboard.

Good luck!

[jimladladlooklike]

You can lower your pups if they're too hot.

Feel like I shouldn't have to do this as it's not a problem with any other pedals... plus I like how hot the pickups are. Are there any other possible solutions?

[ElectricDruid]

Also, I have a Westone Thunder with the loudest pickups ever. So so loud. The pedal doesn't seem to like this. When The gain isn't on full you sort of lose the front end of each note/chord, especially on lower strings...

This doesn't sound right to me. A really hot pickup would just crunch the op-amp even more, so you might have a pedal where you can't turn it down much and the knob goes from "pretty distorted" to "utterly mental".

But that doesn't sound like what you're describing at all, so I think there's still a fault on the board somewhere. Sometimes problems that appear and then disappear are caused by caps, since they can charge up and alter the DC levels in a circuit. Depending on the size of the cap, that can happen over several seconds or even minutes, or much faster, on every note or even every cycle of a waveform. So I'd check the caps, and I'd probably be most suspicious of C5 and C6 for starters, and C13 for seconds.

HTH, good luck!