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Yesterday, a pair of Ampeg SVT4-Pro amps came into the shop, needing quick service for a rental this Saturday. Both had Master Volume problems....intermittent, noisy. One was an older unit in our inventory, having the EQ slide pots that aren't meant to move like they did when brand new, though that problem is seldom the reason one shows up for repair. The older unit with those dodgy sliders had loads of solder joint fractures on the preamp PCB assembly, so repaired all those joints found all over the board, besides removing the MV and Gain pots from the board to apply contact cleaner and exercised to restore their function. And, was able to restore the intermittent behavior of some push buttons. About all you can do with those is spray cleaner in from the front side of the shaft at the body of the part, then exercise the dickens out of them until you see the cleaner has made it's way inside.
I did pull all of the EQ sliders off this older unit, having been down that tedious road many times. Clean the resistance tracks, and apply a liberal amount of thick red grease onto the mechanics of the slider actuator so it moves nice and smooth again. Then, put them back together and fold the tabs back over to hold them together, not over-tensioning the mechanics, which DOES affect the mechanics. I don't know just what it is with those cheap slide pots. When brand new, or still in the 'new' state, you can freely move the actuator lever from the end of the lever and the control smoothly moves without binding. As they age, that behavior goes away, and they then move like the cheap slider controls found in the UREI 527, 529, etc graphic equalizers....which are just horrible and don't belong in a Pro Audio product.
So, this morning, there were now THREE Ampeg SVT4-Pro amps back in the shop. The two I had just repaired and cured of their ailments, plus one more that wasn't here. All new and different problems. I didn't hear or find anything objectionable with the two I repaired yesterday. I always listen to what I service, and play bass thru them to be sure they're solid and road-worthy. But, the Rule of Three's don't care about that. Always something else to propagate and run amuk. Ever notice how an amp, once you've partially disemboweled it, the rest that you don't pull apart, since there wasn't any reason found to do so, gets jealous and pitches a fit after the section you treated is now solid and healthy? Electronic virus? Put them back together & move them back to where they're stored up on the shelf, and a disease spreads amongst them.
Anyway.....does anyone know the secret to restoring the EQ slide pots on the Graphic EQ's used in Ampeg SVT2-Pro, SVT4-Pro? The SVT3-Pro has shorter versions of the longer ones used in those models, but after aging, has the same ailment. I just visited the aisle where all of our rack-mount amps NOT already in road cases are stored, and only those in the Ampeg SVTx-Pro series have this ailment. All the other mfgr's bass amp having eq sliders all move with the greatest of ease. Sigh.............
I did pull all of the EQ sliders off this older unit, having been down that tedious road many times. Clean the resistance tracks, and apply a liberal amount of thick red grease onto the mechanics of the slider actuator so it moves nice and smooth again. Then, put them back together and fold the tabs back over to hold them together, not over-tensioning the mechanics, which DOES affect the mechanics. I don't know just what it is with those cheap slide pots. When brand new, or still in the 'new' state, you can freely move the actuator lever from the end of the lever and the control smoothly moves without binding. As they age, that behavior goes away, and they then move like the cheap slider controls found in the UREI 527, 529, etc graphic equalizers....which are just horrible and don't belong in a Pro Audio product.
So, this morning, there were now THREE Ampeg SVT4-Pro amps back in the shop. The two I had just repaired and cured of their ailments, plus one more that wasn't here. All new and different problems. I didn't hear or find anything objectionable with the two I repaired yesterday. I always listen to what I service, and play bass thru them to be sure they're solid and road-worthy. But, the Rule of Three's don't care about that. Always something else to propagate and run amuk. Ever notice how an amp, once you've partially disemboweled it, the rest that you don't pull apart, since there wasn't any reason found to do so, gets jealous and pitches a fit after the section you treated is now solid and healthy? Electronic virus? Put them back together & move them back to where they're stored up on the shelf, and a disease spreads amongst them.
Anyway.....does anyone know the secret to restoring the EQ slide pots on the Graphic EQ's used in Ampeg SVT2-Pro, SVT4-Pro? The SVT3-Pro has shorter versions of the longer ones used in those models, but after aging, has the same ailment. I just visited the aisle where all of our rack-mount amps NOT already in road cases are stored, and only those in the Ampeg SVTx-Pro series have this ailment. All the other mfgr's bass amp having eq sliders all move with the greatest of ease. Sigh.............