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McMeat Problems

Started by ThisBrian, December 27, 2004, 03:59:05 PM

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ThisBrian

I built a McMeat from the most current PDF < http://home.planet.nl/~remke063/mcmeat.pdf >and for simplicity followed the diagrams here < http://pisotones.com/Meatball/psst/meatball-psst.html > for connecting the pots and switches. Everything looks correct and signal passes through the circuit but it doesn't function properly. The filter LED only lights up with the switching of the sweep switch and with the mode switch in the right position it's somewhat of a fuzz pedal with the other knobs having slight effect on the sound. With most settings the signal is the same as the bypassed signal. I've double and triple checked my connections but I can't see anything wrong... Any ideas?

Joep


ThisBrian

Quote from: JoepDo you have the wiper (middle pin) of the Sens pot also wired?

Doublecheck these pictures:

http://pisotones.com/Meatball/psst/meatball-sens-medium.jpeg
http://pisotones.com/Meatball/psst/meatball-bandwidth-medium.jpeg

Bye,

Joep

Yes, that's how I have it wired. I might have the bandwidth switch wired wrong in that the positions are wrong... I think they're right: On "off" the there is no connection to the sens pot, on full it connects to "Sw1-1" and on 1/2 it connects to "Sw1-2." I'm really scratching my head on this one  :?

Joep

Ok, well judging from your description the envelop detector is not working. That's the circuit build around IC2, so the bandwidth switch is indeed an other good place to look.

Good luck,

Joep

ThisBrian

Your "good luck" probably did it because I just got it working. I had the sweep switch wired improperly and also -- should've looked at the schematic closer -- wired the switch to pot connections backwards (oops  :oops: ) I suppose it's explained in Spanish that the switch to pot diagrams are oriented from the back unlike the pots by themselves. Still have what might be a slight problem. When I switch the sweep up or down the pedal shorts out then comes back to life. I used shorting rotary switches... should I have used non-shorting? Thanks :D

Joep

Hi Brian,

I'm please to hear it's working.

You need a so called, break-before-make switch, otherwise indeed you have a short. Check the schem and you will see Sw2-A1, Sw2A2, Sw2-B1, Sw2B2, Sw2-C1 and Sw2C2 are connected together for a short moment, causing the Sw2A and Sw2C connected together also. A nice short between ground and +9V......

bye,

Joep

ThisBrian

Ah, indeed. I'll need to replace these switches and then I'll be good to go. Thanks for the help Joep, and for designing the layout and pdf -- the one I should've payed more attention too -- in the first place.

jaman

Quote from: ThisBrian on December 27, 2004, 03:59:05 PM
I built a McMeat from the most current PDF < http://home.planet.nl/~remke063/mcmeat.pdf >and for simplicity followed the diagrams here < http://pisotones.com/Meatball/psst/meatball-psst.html > for connecting the pots and switches. Everything looks correct and signal passes through the circuit but it doesn't function properly. The filter LED only lights up with the switching of the sweep switch and with the mode switch in the right position it's somewhat of a fuzz pedal with the other knobs having slight effect on the sound. With most settings the signal is the same as the bypassed signal. I've double and triple checked my connections but I can't see anything wrong... Any ideas?

I have the same problem building the McMeat...

I have triple checked my connections and everything seems ok. I also changed all the resistos, capacitors and diodes with new ones...just in case...

Does anyone know if the MC1458P (that I'm using) is the same with the LM1458 ? could this be the problem ?

The only thing I have not checked if it is fault is the VTL5C3 's...because I haven't other...

thank you

stobiepole

Sounds right...the Pisotones drawings are a little unclear. Wire up your McMeat according to the schematic and you'll be fine. Mine was the same until I redid the wiring. There's some mistakes in those drawings, but I never bothered to check where the problems are.

jaman

Quote from: stobiepole on January 30, 2007, 06:35:11 PM
Sounds right...the Pisotones drawings are a little unclear. Wire up your McMeat according to the schematic and you'll be fine. Mine was the same until I redid the wiring. There's some mistakes in those drawings, but I never bothered to check where the problems are.

I re-checked again all the wirings, as it is in the schematic...

Nothing... :icon_sad:

I checked also the VTL's...there seem to work ok...

My only last hope is the chip...I use MC1458P instead of LM1458...is there a chance it might be this the problem ??

stobiepole

You're sure that the pots aren't back to front? There's definitely errors in the Pisotones drawings, so if you used them and then checked it the schematic and didn't find anything, you've missed it...see this thread:

http://www.diystompboxes.com/smfforum/index.php?topic=44290.msg322024#msg322024

Chris

ThisBrian

Wow, this is old. You're using a single opamp (if the datasheet I found was correct). You'll need a dual, any of which should work fine.