micro-amp debug

[olslick]

i just finished a ggg micro-amp clone and i'm not getting any sound out of it when engaged. bypass and led work. no solder bridges, all resistors correct. diode is oriented correctly, and i believe the capacitors are as well (the kit comes with tantalum caps and i believe the line indicates positive). wiring all looks correct according to wiring diagram. the ic is oriented correctly, i believe that the little circle indicates lug 1, in which case the correct lugs are going to where they need to go as per the schematic at ggg.

i've run the audio-probe through the circuit and i lose signal where r3 connects to the 3rd lug of the ic. that lug has signal, but no farther.

[olslick]

starting off small, are the tantalums correct? and is the ic placement correct? (little hole facing up and left to the top of the pcb)

[olslick]

could the ic be blown? i flipped it around to see if that would work and it made this weird "thunk" kind of noise when i hit the low e string kind of hard. but, the way i have it now, which is the way i originally had it, looks schematically correct with the 3rd lug connecting to r3... i'm using sockets, by the way, and i've already ordered another ic just in case. i was going to give this to my dad as a christmas present so hopefully it gets here in time. i ordered the same ic that ggg sent me in the kit, however it isn't the same number the schematic calls for. is that kosher? the schematic calls for a TL061 and it came with a TL072, is that something i should have compensated for somehow?

[petemoore]

could the ic be blown? i flipped it around
  The pinout of 8pin IC's is critical. Iow, yes, if you reverse polarized it, could or would get damaged.
  to see if that would work and it made this weird "thunk" kind of noise when i hit the low e string kind of hard. but, the way i have it now, which is the way i originally had it, looks schematically correct with the 3rd lug connecting to r3... i'm using sockets, by the way, and i've already ordered another ic just in case.
  These come in handy for finding out if ''that'' one is blown.
  i ordered the same ic that ggg sent me in the kit, however it isn't the same number the schematic calls for. is that kosher? the schematic calls for a TL061 and it came with a TL072, is that something i should have compensated for somehow?
  These are two different pinouts, the TL061 is a single opamp, the TL072 is a dual opamp. The pinout is critical with these chips, find the right kind and verify the pinout is correct. Reference the data sheet for the chip, find the +input and -input pins to be sure they are correct with the schematic and layout.

[anchovie]

the schematic calls for a TL061 and it came with a TL072

The TL061 is a single op-amp, the TL072 is two op-amps in one package. They aren't interchangeable so it looks like GGG sent you the wrong chip.

If you ever need to know if a part can be used as a substitute, Google the part number to find a datasheet so you can confirm function and pinouts.

[Tony Forestiere]

Can you post the schematic so that we can tell if they have only used 1/2 of the dual for the circuit's original single?

[Tony Forestiere]

Sorry :icon_redface:Isee it now.
TL072 is the wrong IC. Try a 741 or 308 if you have one. Won't sound great, but should work until you get your single opamp.

[olslick]

tht sucks. now i'll have two of those wrong ics. hopefully, ggg can send me one because they didn't have any on pedal parts plus...