All Of Those Ebow Schematics You've Seen ARE WRONG! (Part II)

I had to create this video to correct a few mistakes I made in Part I, and to clarify some things about the circuit which were not initially clear to me when I made Part I. I think I have everything figured out as much as it is possible to do with only pictures and hacked apart specimens to get my info from.
Part I can be found here: • All Of Those Ebow Sche...
THIS VIDEO IS FOR EDUCATIONAL PURPOSES ONLY.

[@kornelispoort6937]

Great video. Regarding the two round pads: If there is no soldermask covering them I would assume they are indeed test points. Locations in the circuit and the way they're laid out (for a test jig) seem to make sense. What is their diameter?

[@VegasCyclingFreak]

I’d say the diameter of those two pads are approx. 1/8”.

[@kornelispoort6937]

@@VegasCyclingFreak Pretty large test points I guess, it still seems to be the most likely purpose to me.

[@VegasCyclingFreak]

@@kornelispoort6937 It may be that they have some kind of test fixture that they insert it into, so they want to make sure there is plenty of surface area to ensure good contact.

[@tenlittleindians]

It's interesting that they would list the exact amplifier chip for their circuit in the patent and then go through the trouble of removing the identifying labels off the actual chips used. Have you tried to measure any thing on the actual chip or tried to remove the chip and then breadboard it and test it using a bench power supply? Even if the chip is dead it may provide some information to verify if it's the amplifier chip listed in their patent. I suspect your broken ebow died originally from a broken connection rather than a faulty amplifier chip. Your integrated circuit may still work on your destroyed unit. I've only recently been curious as to how these work and I got to say; that's not how I would have gone about it. I may have to build my minds version which invisions an AM radio transmitter outputting it's signal into a coil and it's input is coil coupled to the guitar pickup too. I would make the feedback adjustable like an old single tube radio designs tuner feedback section that they use to pull in weak stations. I am thinking about building my radio transmitter/receiver using a tank circuit with a quartz crystal resonating at my chosen carrier frequency. It may not go anywhere but parts are cheap and breadboard circuits allow plenty of room for changes.😊

[@VegasCyclingFreak]

I don't know if they removed the markings from the IC chip or not. To get to the circuit you have to pick it out of literally rock hard goop, so it's almost like chipping away rock from a fossil. I didn't dissect any of these things myself but I think it's reasonable to expect that the markings on the IC chip wouldn't survive this destructive process. The patent documents do not say specifically that it's an LM386. It only says "the circuit includes an operational amplifier which may be any one of a plurality of commercially available operational amplifiers". From the schematic it's pretty obvious that it has to be an LM386. I think they may have purposely tried to be confusing on the schematic, because some things don't quite add up. The patent documents do mention something about adjustable feedback but that didn't make it to the final design of the thing... maybe they felt it was not necessary. Your guess is as good as mine.

[@tenlittleindians]

@@VegasCyclingFreak I based my comment off your patent drawings which list the actual amplifier chip. Did you alter those drawings to include this information? To get around the epoxy potting problem you could take a Dremel tool with a cutting disc and simply cut the traces between the individual legs of the chip to isolate them for testing. It's still common practice for manufacturing to use off the shelf parts and mill off the markings to make it harder to reverse engineer their designs. They got these priced about perfect to eliminate pirating and home building copies. At $99 bucks it's not practical to buy all the parts and build one from scratch even if you had the exact circuit parts list and layout. It knocks out the profit incentive for even the Chinese to copy the design and sell them cheaper.

[@VegasCyclingFreak]

@@tenlittleindians If you are referring to the patent I show in the video, I put that on there in red. Nowhere in the patent do I see any specific components listed. You can read thru the whole thing, it's on my website here: www.diyguitarist.net/Misc/Patent_4075921.pdf Whoever dissected the plus ebow originally didn't know what they were looking for because no one had ever tried to reverse engineer one. A lot of the circuit board was damaged, and some of the parts got broken too. The ENTIRE circuit board was encased in whatever goop they used. I had to pick a little bit off one area which was left behind, and it was not anywhere close to easy getting it off. I'm surprised they were able to limit the damage to what they did. The coils were completely destroyed because they were also completely encased in that goop. Most of the "magic" of the ebow circuit lies with the coils. They have to be something very specific for it to work, and to work reliably. If I need to cut a track on a PCB I can just use an Exacto blade. Done it many times on my own self-etched PCBs to fix mistakes or on pedal mods. Concerning Chinese copies, it's too late for that. The ebow isn't the only handheld sustainer on the market anymore. There is also the "Joyo" and TC Electronic "Aeon" on the market now. Probably are all more or less the same circuits, but I don't know that for a fact.

[@AngelLaHash]

i have no hope how to understand the Email.. ebow Data 2002-12-05.pdf .. DIYGuitarist@ and then soudnds like M-Bar and that with a Q