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TomWhitwell / Spring-Reverb-Mk-2

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Mixer Pot and LED are not working #9

Open Blackman-Robotics opened 5 years ago

Blackman-Robotics commented 5 years ago

Hello,

i just bought a Spring Reverb MK 2 only with the Brick for first. I soldered everything together and tested it. So my issue is, that the mixer pot has no effect to the sound from the input. Only when i´m opening the feedback pot, the i have the feedback sound and the tilt pot works as it should. Also when i´m using a cv signal, there is no effect. I just measured the TL072 and i see, that the 12V for the mix pot are comming and the pot is also working. After the voltage divider i have also round about 3.xx V. But on the input on pin 3 of the TL072 i have zero volts. and the output has always -10V, so the led can´t work. I have no spare TL072 IC´s but i think on the pulldown resistor R23 i lost all my voltage. Maybe you have an idea? Thanks in advance!

Dennis

TomWhitwell commented 5 years ago

Sorry to hear that. Input pins on op amps normally read 0v because they're a virtual ground (it's quite normal) However, the -10v output is not normal. There's nothing obvious I can think of - we get fairly few issues with this build, so it could be something simple like a missed solder connection or a reversed chip or reversed LED somewhere. Sorry I can't be more helpful - check the schematic: https://github.com/TomWhitwell/Spring-Reverb-Mk-2/raw/master/Collateral/SpringReverbMk2-Schematic.pdf

Blackman-Robotics commented 5 years ago

Hello Tom,

thanks for the fast reply. Yes i have already look into the schematics and also resoldered the points which are responsible in this case. The IC´s are fitting correct. I also exchanched the two TL072, but the same issue. The LED is also correct. Maybe I have two broken TL072. I will organize me two new a i will check it.

Have a nice evening!

Blackman-Robotics commented 5 years ago

Hello Tom,

I solved the problem :) I had a bad connection on the PCB from R21/R22/R23 to pin 3 of the TL072, so the TL07 had an open input. This explains the inverted voltage on the output. I think the conduktor track was faulty, I made a bridge connection an then i had the +10 volts, but the proplem was still the same. Then i found out, that the LED was broken. I had no spare, but I made also a bridge connetion over the anode and kathode, then the reverb works. Have a nice weekend :)