Gemini III dual fuzz dissected

[Earthscum]

Just thought about this... on the "mystery" Q7, can you get a diode reading? It almost seems, by the voltages, that it's PNP. Maybe you can get lucky and it will give up it's identity on-board.

eta: looking at it, if it were a PNP, I don't think it would be working... it would be biased off.

[digi2t]

Just thought about this... on the "mystery" Q7, can you get a diode reading? It almost seems, by the voltages, that it's PNP. Maybe you can get lucky and it will give up it's identity on-board.

eta: looking at it, if it were a PNP, I don't think it would be working... it would be biased off.

I figured that the voltages would go a long way for someone more gifted than myself to maybe nail this one down. Like I mentioned before, the face has been ground down thus erasing the identity. Maybe an NPN, but an ECB pinout? I was also wondering if this could be a jfet, but I didn't want to risk taking it out to analyse with the Peak. Just separating the boards for the tracing was a major undertaking. In any case, I put this portion of the circuit on the breadboard using a 2N3904, and it worked fine.

It's too bad that my bench is loaded right now, or else the breadboard would be running this right now. I'd like to build this, but using Russian trannies, I've been stocking up on them. Maybe call the clone the "Soyuz Dual Fuzz", rekindle the great fuzz... err... space race.

Then I'll have to send it down to my bro Jimi for the video shoot, of course.

[Earthscum]

I was just going through Mouser looking at SMD Jfets and it dawned on me that this MIGHT be a P-Channel Jfet, but I'm not exactly sure on how they function, or would function in this instance. Just a thought... it's the ground face that's throwing me, lol. It's either something special, or something mundane, but either way I want to know if the cat lived or died, dammit! 

[Chugs]

Maybe it is a BC183? It is NPN with a ECB pinout.

[Earthscum]

If you look at his original drawing, it is like a NPN (EBC) that is backwards (and could be). The pinout, if NPN, would actually be CBE. The voltages reflect this, the base is 1 diode drop above the "collector" (should be NPN=Emitter). It would either be a CBE pinout, DGS Japanese fet (but gate would be pulled low rather than high) or PNP (but again, the base is wired backwards). UJT or something?

[digi2t]

What might be throwing you guys off, is the fact that I used a transistor symbol in the schematic. Like I mentioned before, looking at the flat side, I'm "assuming" that it's a transistor with an EBC pinout.

The voltages that I've provided for this "transistor" are also take from left to right, "assuming" that they are the EBC voltages.

I just wanted to clear that up, before anyone trips on their shoe laces. When I get some time, I'll breadboard a fet in here, and see what happens. Personally, it wouldn't surprise me if it's something banal like a 2N3904, or something similar, here. After all, they even took the time to grind the numbers off the tranny and fet for the Millenium bypass, like we wouldn't figure out what THAT was. I think maybe this is a similar "red herring". Besides, look at Q4 (and Q1 for that matter), they all share the same emitter resistor value. I love a conspiracy theory, just as much as the next guy, but I'm leaning toward BJT here.

Thanks for taking the time to brainstorm this guys.

[Earthscum]

Actually what is throwing me off is the reversed pinout.

[dorrisant]

If you guys think the last schematic is verified, I would be willing to try to come up with a pcb trace...

Tony

[digi2t]

If you guys think the last schematic is verified, I would be willing to try to come up with a pcb trace...

Tony

Hi Tony,

The schematic, insofar as where the lines are going, is fine. The only thing up in the air right now is Q7, but that wouldn't affect a PCB trace at all. Although, a single sided PCB of the entire circuit will require a larger enclosure than the original. No biggie, for me, heck, I planning on doing this on vero  .

If you really want stay true to the original, you can even use my hand drawn versions, at the beginning of the thread. These are taken directly from a unit. The upper board is single sided, but the lower board is double sided. The component side traces on the lower board are highlighted in red. The pots are mounted directly to the PCB, as well as the miniature toggle switches. Along with the components, you might have enough dimensions to scale the sketches properly. The connection points on the edge of the boards labelled 1 thru 7, should also line up between the two board when they are laid one over the other. There is solid core wire used here as connectors / stand-offs. Both boards use a ground plane to ground whatever components need it. Looks great in the original, and saves on tracing as well.

Cheers,
Dino

[dorrisant]

If you have any gutshots, you could post them or pm me... if you don't have any, just let me know and I will proceed anyway.

Tony

[digi2t]

If you have any gutshots, you could post them or pm me... if you don't have any, just let me know and I will proceed anyway.

Tony

I took a trace side shot of the top board, but for some unknown reason, I neglected to take a trace side shot of the lower board  .

I`ll post the top board pic later.

[Tony Forestiere]

Watching with interest. Nothing to really add, but:

...but either way I want to know if the cat lived or died, dammit! 

Of course it did! 

[digi2t]

OK, here are the pics. I suddenly remembered why I didn't bother with trace side shots of the lower board. It's because the pots and switches are mounted on the board directly, and I was not prepared to desolder everything for that. I do have component side shots though. Like I said, you can use the sketches to run the traces as well.















Hope that helps you out.

Cheers,
Dino

[Skruffyhound]

I'll just subscribe to the thread
Good work.
Carry on as you were.

[dorrisant]

Oh yeah! That will help... Great pics!
Gonna see what I can do with it this weekend.

Tony

[digi2t]

Oh yeah! That will help... Great pics!
Gonna see what I can do with it this weekend.

Tony

Cool. Let me know if you need any more info. I`ll try tp help any way I can. I really want to clone this sucker, it`s a great sounding fuzz. If you make some boards, I`ll buy a set or two from you.

Cheers,
Dino

[dorrisant]

Hey guys, check this for errors if you don't mind. Don't beat me up too bad if things look too tight... I usually just cram it all in and then spread it out to be a little less crowded.  I tried to get away with as few jumpers as possible... it is single sided though, so it is what it is. Let me know if I've screwed anything up. I did not double check it before calling it a night and I just wanted to post it and get the ball rolling. So here you go...






Tony

[digi2t]

Nice Tony, real nice.

I'll go over it tomorrow. Just one thing, might be a good idea to mark the transistor pins (e,c,b) on the layout, just for the sake of clarity.

I'll let you know what I come up with. Actually, it will also help me with a vero layout as well.

Cheers,
Dino

[dorrisant]

I was gonna mark those trannies but ran out of energy and time. I will mark them later. I also want to re-route the ground trace on the bottom right corner... just to make the board a tiny bit smaller if needed.

I'm glad you might find it useful. Looking forward to your comments and suggestions.

Tony

[glops]

Carry on Gentlemen, would love a PCB layout for this.  I think my feeble brain would take years in delivering a good layout for
the peeps.  Lately, I have been designing my own layouts for boards and using other free ones here and on the webs. Sometimes
I'll get some boards from musicpcb or bean.  I like when someone make a new diy transfer. Makes me feel in intune. A board for this
and the Wem Project 5 would make for some great summer fuzzies.....