CRATE GFX -50TT

[EDWARDEFFECT1]

I HAVE A CRATE GFX50 THAT THE EFFECTS DON'T WORK.AFTER LOOKING AT THE SCHEMATIC THERE IS A RESET ON THE CHIP.DOES ANYONE KNOW THE PROCEEDURE FOR DOING THIS RESET?...THANKS...ED!!

[Enzo]

"RESET" is not a procedure.  it is a common function in digital circuits.  All it is is a wake up reset.  When power is first applied, the circuit waits a second before letting the DSP program start to run.  That insures the power supply has had a chance to stabilize.


Apply a nice strong signal to the amp input.  Is signal then present on pin 7 of U4?  Or at pin 7 of J11?  (Electrically those are the same)  If there is no signal there, then the FX has nothing to work with.

Likewise the signal at pin 8 of J11 - the output from the FX card - is ther signal there?  Does it make it to the top of the FX control P17?   How about the wiper of P17?

Inject a signal at the wiper of P17, even if it is just hum.  Does it come out the speaker?

Those tests check the signal path to and from the FX card.

If the card itself is faulty, then verify the 5v regulator on the card is indeed producing 5v.

There are two reset generator ICs, U4 and U8.  Look at pin 2 of each, and verify that teh voltage there is something like +5 and not ground.

[EDWARDEFFECT1]

thanks  ENZO  for the heads up on reset and you get the credit for me fixing this amp.the ic in position u4 was bad. the schematic i had said u4 was a tl-074 ic but it was a tl-072. i replaced it with a jrc-4558d ic which has the same pin configuration(i didn't have any tl-072 laying around)and bingo it is running.i ran a signal tracer in the input and checked for signal on pin 7 and had no signal passsing.i then checked the voltage on pin 7 and had no voltage.so i figured the chip was bad as i believe pin 7 is an output pin.thanks again ENZO!!!

hope the capitals on your name are o.k.i did my first post in capitals by mistake! this time only your name is in capitals as i thought it was important that the wisdom made know to me was by my friend and the friend of many other posts i read.....thanks.....ENZO.....ed!!!!!