WARNING!! Mini Eliminator mod is incorrect

[Mike(Mont)]

Yet another proof I do not know what i am doing. It didn't hurt anything, but something is not right with the mod I posted. The ground wire to pin 11 is just not right. That goes to a capacitor and I don't know what the problem is, but when I removed the wire from pin 11 the tone got louder. So I removed both wires plugged the IC8038 back in and will just use it as stock for now until I learn more about the issue. So now I think I still might have a chance to clear this up and try to mesh this with my contraption some day down the road but not now.

[Mike(Mont)]

I really like the precision of the DDS signal generators. Wish I knew more electronics about the bi-polar power supply. I suspect that could be the area where the problem is. Something strange was happening when I increased the voltage/amplitude of the DDS, the voltage dropped at the output Or maybe it's something to do with the inverter function of the NMOS or a combination thereof. Whatever it is, I'm over it. Not even sure I need it, anyway.

[Mike(Mont)]

I'm going to go back and take a second look at this issue to see if I can get something I feel more comfortable with. Basically, I plan to measure the voltages, etc. and see if I can match the original stock version. My feelings are that these need to be the same or else it might not work like it was designed. The mod I made does work just not sure if it is correct.

[Mike(Mont)]

Know when to say "When". I'm there. It's over my head and I don't need to drown right now. So someone else will have to carry the flag on this one. I still think it's doable, just not by me right now. Ignorance speaks loudly today. But never say "Never".

[Mike(Mont)]

They say the most ignorant are those who don't know what they don't know. I can assure you I am not in that category today, anyway. I know very well that I don't know much of anything about the Mini Eliminator II. That means I have much to learn.

[Zura]

Dear Mike
on Mini Eliminator II modification you posted "I'm going by Carl's schematic, or at least what I think I understand about it. And Bob Fitz said it wasn't correct"

let assume the Carl's schematic is wrong (or maybe just some wrong connections).
you are modifying Mini Eliminator base on Carl's schematic .

Could you draw a schematic base on your own Mini Eliminator ?? (Even draw by hand)

I'm an Electronic Engineer,I'll do my best to help you.

first thing needed to modify ME-II is a correct schematic.

I think some thing is wrong with Carl's schematic.

Regards,Zura

[Mike(Mont)]

Probably cannot get a schematic for you. I would have to disassemble the wiring so I can use a magnifier to see it. It's SMT and some of the components can't see any markings on them. Can't even get a good photo of it because the board is turned over face down and wires/ribbon are in the way, and i don't want to risk damaging it.

That mod I did is probably okay. I don't know enough about the bipolar power supply and probably had my DDS signal generator set wrong offset. Those cheap DDS do not adjust well or at all. So I plan to do some more checking and studying. Just an example i learned that 15K resistor damps the square wave and cuts off the corners. You see I am very ignorant to all this.

Thanks for your offer to help. If i ever get the thing apart I will let you know.

BTW, you can view Carl's schematic go to the geotech1.com click on LRL then click Reports, then click Mini Eliminator II.

[Qiaozhi]

Originally Posted by Mike(Mont)

It's SMT and some of the components can't see any markings on them. Can't even get a good photo of it because the board is turned over face down and wires/ribbon are in the way, and i don't want to risk damaging it.

I cannot believe that Bob Fitzgerald would have the knowledge to create an SMD design, so I suspect the PCB is probably salvaged from some other piece of equipment, and "adapted" to look like something that might actually work. Which would explain why Carl's schematic and your particular device do not tie up. In fact, I'd be very much surprised if any of these devices look anything like each other, unless Bob Fitz got hold of a job lot of surplus junk.

[Mike(Mont)]

Whatever, all I know is I'm over this mod thing and the hybrid. Best if I keep it stock so I can compare it with my contraption.

[Zura]

Originally Posted by Mike(Mont)

Probably cannot get a schematic for you. I would have to disassemble the wiring so I can use a magnifier to see it. It's SMT and some of the components can't see any markings on them. Can't even get a good photo of it because the board is turned over face down and wires/ribbon are in the way, and i don't want to risk damaging it...............

ok,i just wants to help on modifying ME-II.
i think that 15K is pull up resistor.
the only modification i can suggest you without schematic,replace 10k potentiometer with 10K Precision 10 Turn Pot. it gives you more accuarcy to set the frequency.

please just look at those 2 transistors, I think one of them is N-MOS and the other one is P-MOS. please check it.

[Mike(Mont)]

I tried to check it but the numbers have been scraped off some of the components and others i can't get to without risking damage by disassembly. Sorry can't be of any help. I can tell you this much, it is different than Carl's schematic. More components.

[Zura]

OK,thanks anyway.

[Mike(Mont)]

If I ever disassemble it, I will let you know. I don't see that happening any time soon, but maybe next Winter. As for the precision pot, there is one there now but it's bearings are sloppy.