Question from a complete novice RE repairing an 80's Ross Analog Chorus

[sunnydayjr]

Hi everyone, I'm a stomp-box enthusiast who knows very little about electronics. I've got a Ross model R88 Analog Chorus (made in Taiwan black model) that I believe just needs a little help to be working. The pedal works in that the sound of affected if the Depth knob is turned manually, but the rate knob is dead and there's no oscilation. I assume it's one of the IC's and fortunately for me they're all socketed and are available for purchase on eBay. There are 4 chips total. The MN3101 and MN3007 I know are the delay chips, but there are also a TL072CP and an LS4558ND op amp. Could anyone point me in the direction of which chip is most likely the culprit? If so, it would be greatly appreciated. Thanks in advance to all who read this!

[Fender3D]

If the sound changes when turning the depth knob, you could assume the MNs are working.
Try swapping the 072 and the 4558 they're pin to pin compatible, and see if something changes.
yes case:
one of the 2 swapped chips is fake (maybe 4558)

nay case:
last week I broke my first pot in 35 years of DIM (do it myself)... so never say never...

[petemoore]

  If it's not the one thing it could be 100 others.
 Could be the chips or something else went wrong with it.
 Read: "Debugging, when it doesn't work", and anything else you can get your hands on, DMM instructions help when finding new or all possible ways to apply DMM, I like to first test for shorts, then apply voltage and measure some potentials.