Mastodon Problems (solved)

[Anonymous]

Yes I saw all this once connected, the switch was in position effect when I made the contacts with the multimeter, but it’s good I think for the 3PDT and the jacks are good because it works in bypass.

Now I have to find what’s wrong with the main PCB that has to make the effect because I still have no sound in position “effect”.

But we advance! 🙂

[Billy]

R8 is the CLR current limiting resistor for the LED 1K8 would be bright 3K3 not as bright you can use any value from 1K to 4K7 depending on how bright you want it

 

I’m at work at the moment so can’t have a good look I would suggest you make an audio probe see the guides link on the homepage for how to build and use one

 

This method will cut your fault finding from hours to minutes a great tool to have and cheap to make

[Billy]

All of your components look to be of the correct value the only one I can’t see clearly is R4 (22K) the colour bands should be

red, red, black, red, brown

 

Looking at the schematic and comparing your transistor voltages to what they should be I suspect you may possibly have a solder bridge or poor solder connection giving you your strange readings

 

Q1 Collector and Q2 Base should have the same voltage being directly connected to each other after R3 (51K) looking at your readings I think they do 1.75v

 

I think your voltages have Q1 and Q2’s Emitter and Collector the wrong way around and what you have as the Emitter is actually the Collector and visa versa your empty socket readings would make more sense that way

 

Q1 Emitter is only connected to ground and the fact you have 5.82v? there again makes me suspect a solder bridge / poor connection somewhere, continuity check Q1s Emitter to ground

 

Check Q1 Collector has continuity with Q2 Base

 

Check each transistor empty socket making sure that each of the 3 socket holes do not have continuity and double check the solder joints on the sockets

 

Check that R3 left side nearest the IN pad has continuity with Q1 Collector ( in red dots below on the pcb image)

 

This will give us an idea of where there could be a bridge or bad connection

 

 

Just for info 2N3904 pinout

 

[Anonymous]

Ok already according to your diagram, I inverted my measurements between emitters and collectors. As a result Q1 transmitter and Q2 base are both at 1.75 V.

I have 5.82 V at the Q1 collector as I reversed when taking my measurements.

I study all your message tomorrow to try to see more clearly!

Thank you

[Billy]

If your initial measurements were reversed then you’d have 5.82v on the emitter of Q1

 

Take Q1 out of its socket and check the 3 socket holes don’t have continuity with each other

 

Weird measurements sometimes indicate no path to ground so check Q1 emitter has continuity with ground if not reflow the socket solder joint and re check  making sure the 3 socket holes don’t have continuity with each other

[Anonymous]

Hello and thank you !

I followed your recommendations and I finally sound in “effect” mode.

It was the transmitter Q1 which was not welded well, now it is well connected to the mass and the pedal works (except the potentiometer WOOL which does not change absolutely the sound when I turn it even having redone the welds. ..).

By cons my R4 resistance is not a 22k but a 24k, its color code is:
red – yellow – black – red – brown.

I do not know if it changes a lot of things, you will probably know me.

I took the values ​​in Q1 and Q2, they still do not correspond to those of the diagram but it is a little better and it gives:

Q1 E = 0 / B = 0.6 / C = 1.34
Q2 E = 0.7 / B = 1.34 / C = 1.70

So I have a continuity between Q1C and Q2B and now between Q1E and GRND.

I have no continuity in the transistors so it’s ok and I have continuity between R3 and Q1C.

It remains for me to find why the WOOL potentiometer does not work.
I tested it at the Ohmeter (on the circuit) and I have two legs that remain at 0.00 Ohm when I turn the potentiometer …

I have another 2k lin potentiometer that dates from my previous test but when I test it it reacts exactly the same way (0.00 Ohm between the same two legs), according to you do I replace it or is it can it come from elsewhere?

And thank you !

[Billy]

Great glad it’s working the transistor voltages don’t have to be exactly the same a few mV won’t make a massive difference

 

To check resistance on your potentiometer measure resistance between the two outer lugs 1 and 3 but remember they have a + or – 20% tolerance so may not be exactly 2K

 

You will get 0v between the middle and 1 outer lug the middle and other outer lug will give you a resistance reading, turn the potentiometer shaft the other way and they’ll be opposite

 

If you are getting 0v between the same lugs turned both ways then the potentiometer may be faulty

 

There is information on how they work in the beginners guide to effects pedal components

 

24K won’t make much difference to a 22K resistor for R4 that is why your transistor voltages are slightly different Q2 collector with more resistance giving you 1.70 instead of 2.3v if it sounds good just leave it

 

[Anonymous]

Well that’s it all works!

I think there was a contact with the chip or it’s me who did not understand the effect of the potentiometer just now …

Case settled! I’m going up the whole box and I’ll plug it into the pedal in 1h see what it’s worth!

I will put a picture when she is pretty!

A big thank you to you and Barry!

[Billy]

Well done on getting it working, it does get easier!

 

You have learned a lot which will be good for your next pedal build

 

As Barry said read the guides a lot is answered in the guides and they’re written with the beginner in mind with links for more information

 

And definitely make an audio probe and a test pedal it makes fault finding much easier and much faster

 

I look forward to seeing your completed pedal

[Anonymous]

Billy,

You wrote “And definitely make an audio probe and a test pedal it makes fault finding much easier and much faster.”  I’ve built an audio probe, but don’t have a test pedal.  Is there a set of build instructions for the “test pedal,” or is this simply a known good pedal?  I have to admit that I’m experiencing brain freeze or similar, but hope someone can point me to the answer.

Thanks,

Bob

[Billy]

The test pedal is basically a pedal without a circuit in it that you can attach your newly populated pcb in, out, ground and power to

 

It saves you soldering your 3PDT in and out jacks and DC jack to your pcb prior to putting it in the enclosure

 

If it tests OK then doesn’t work when you wire it into your enclosure 9 times out of 10 you then know you’ve made a mistake with your offboard wiring to the 3PDT jacks DC jack etc

 

If it doesn’t work then with a test box with an integrated audio probe you can immediately start debugging as Barry says with the flick of a switch using the integrated audio probe

 

I have been working on an image showing how to make one from tagboard effects this one

 

http://tagboardeffects.blogspot.com/2014/09/test-box-20.html?m=1

 

I’ll get it finished when I get a minute and post it, it’s simply a visual of the above instructions

 

 

 

 

 

 

 

 

 

 

[Anonymous]

I recently ordered the mastadon fuzz via musikding. I am fairly new to pedal building but can follow an instruction and have several working projects. As you can see on the pictures the 3PDT board that musikding supplied me with is slightly different than the one in the manuel. I don’t know where to connect the black and red wires from the main pcb to the 3PDT board and where to connect the red and black wire from the 9V power supplie to the 3PDT board. Can I connect them in the same holes (the gnd en 9V+ hole of the 3PCBT board’?

[Author]

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