Troubleshooting treble booster

[Subropontes]

I just built a rangemaster kit following the layout provided and I did something wrong that I’m being too stupid to realise what it is.
I have signal going through when bypassed, but when I turn the effect on it’s super gated and the knob doesn’t do anything with or without the battery and when I connect the battery the wires on the battery snap start getting quite hot. Where’s my mistake?

[antonis]

First suspect is reverse polarity of reverse polarity protection diode..

[ElectricDruid]

I know it's a simple circuit, but that's a nightmare to debug. Sorry.

Antonis' first guess is pretty good if "the wires are getting hot". In that case, there must be some *serious* short across the battery, and the polarity of the protection diode being wrong is an obvious way that could occur. However, from the photos, that doesn't look (from here) to be the case. Check it out carefully in reality, because it's hard to see from just a photo and a couple of angles.

After that, take the battery off and use a multimeter to test the resistance between the two terminals on the battery clip. Since it's shorting and getting hot, we're expecting something very low indeed. If it were the diode, you get this result with the probes one way around, but *not* with the probes the other way around (it's a diode, after all! only conducts in one direction!) so that would be a good test to do.

[andy-h-h]

Separate to the power issue

1) Have you checked the pin out of the transistor?  Soviet-era transistors are sometimes BCE.

2) Stereo input jack to switch power, but I can only see two connections.  Are you relying on the enclosure to ground the input jack?

3) Not sure about the switch wiring - can't see it very well, just doesn't look right.  I am one coffee behind where I should be at this time of morning...     

[Subropontes]

Here's a better photo. I double checked everything and it seems to be just like the reference photo. Could the reference photo be wrong (which I think is unlikely)?

I checked the pinout with my Atlas DCA55 and it showed me the same as this:

[andy-h-h]

So this is running positive ground - as a MP38 is NPN transistor.   The SFT308 shown in the layout is PNP, meaning all the wiring would be for positive ground. 

I take it you have taken this into account.

What are you getting for voltages?  If you have a DCA, you must have a multimeter?

[Subropontes]

Sorry, wrong photo. I'm doing this with very little sleep so maybe that's the problem. Haha
I just went back to check and the pinout on the MN21 I used is the same as the photo but with the E and the C the other way around, which is how I wired it so the transistor pinout is correct.
Just checked and I'm getting no voltage on the transistor.

[andy-h-h]

OK - so you are using a PNP transistor - positive ground circuit.   I can see a black wire from the battery connector running to the ring on the stereo input jack.   Normally for positive ground, this would be the red wire (V+).

I can't see a ground connection on the stereo input jack.  I also can't see how power is reaching the pot (to power the transistor) with that switching arrangement.   

Oh and silly question - I’m assuming you are testing with a jack plugged in to turn the circuit on (I’ve forgotten to do this more times than I care to admit)

[Subropontes]

Right, there's my issue and I'm being an idiot about it. I have the negative wire from the battery snap on the ring of the input jack like I would on a NPN pedal and the positive wire from the battery snap going to ground on the board so the battery wiring makes no sense whatsoever. Haha
So hang on, where does the negative side of the battery goes on that board? Do I solder it to the right lug that is connected to the pot? And the positive wire is soldered to ground on the board in the reference photo, do I switch that to the input jack's ring so it doesn't use the battery when not connected?

And yes, I'm testing it with a cable plugged in and I grounded the input jack to the output jack after taking those photos.

[andy-h-h]

I have the negative wire from the battery snap on the ring of the input jack like I would on a NPN pedal and the positive wire from the battery snap going to ground on the board so the battery wiring makes no sense whatsoever. Haha

Well this explains the heat - you shorted the battery, which can be a little dangerous.   

Grab a schematic via google and compare it to your build to work out where V- & V+ need to go.  If you look at the layout you're using you can see where they connect.   On your build, take note of the pot and the pin connections vs the layout / schematic - this should explain the lack of power to the transistor. 

As for the input jack:  Connect V+ / red wire to the ring so the circuit is only on when plugged in.   Ground (the sleeve) stays as ground, as per normal.   Tip is signal, as per normal.

Hope this gets you sorted.  You battery could be cooked by the way. 

Given that you are using a battery and don't seem to have any plans to plug this into a pedal power supply, the diode is not needed.

[duck_arse]

if that prominent yellow wire is carrying signal, it is connected to the sleeve, and probably hence ground, on that mono jack.

[Subropontes]

The yellow wire is ground to make it complicated. I did the whole thing with no sleep and messed up every step of the way. Haha
The problem was the battery snap connected to the wrong place.