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Unlatch Mod?

Started by 12StringStratMaker, January 25, 2005, 07:16:30 PM

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R.G.

Correct - clip the black lead to signal ground and leave it there for all measurements.
R.G.

In response to the questions in the forum - PCB Layout for Musical Effects is available from The Book Patch. Search "PCB Layout" and it ought to appear.

12StringStratMaker

Ok here goes:

Stock:
 Q7:   Collector: 0.614 (off)    0.028 (on)
         Base: 0.024 (off)    5.80 (on)
         Emitter: 0.000 (on & off)
 Q5:   Collector:  0.009 (off)   0.659 (on)
         Base: 5.80 (off)   0.079V (on)
         Emitter: 0.000 (on & off)

Mod: (NP = Not pressed, P = Pressed)
 Q7:   Collector: 0.028 (P & NP)
         Base: 0.000 (P)   8.58 (NP)
         Emitter: 0.000 (P & NP)
 Q5:   Collector: 0.659 (P & NP)
         Base: 0.079 (P & NP)
         Emitter: 0.000 (P & NP)

OG

I don't know if it could be usefull, but i have the vb-2 schem.
I always thought that the  "unlatch" possibility was  great for vibrato or tremolo, and only boss did it, once.
Too bad.
O G

R.G.

OK, that helps.

QuoteStock:
Q7: Collector: 0.614 (off) 0.028 (on)
Base: 0.024 (off) 5.80 (on)
Emitter: 0.000 (on & off)
Q5: Collector: 0.009 (off) 0.659 (on)
Base: 5.80 (off) 0.079V (on)
Emitter: 0.000 (on & off)
Emitters are dead zero, which is correct. It appears
that the collectors of the two transistors move between about 30mv when the transistor is turned on and 0.6V when the transistor is off. I would have expected the collectors to get much higher - 5.9V is what the simulator model shows, and about what my head tells me ought to be there, so I'm suspicious of that collector voltage measurement.  But you say it works that way, and I don't have the hardware to test.

...oh... duh... what was I thinking?

You were reporting correctly, you just have the wrong pinout. What you are calling the "base" is really the collector, and what you are calling the collector is really the base.

Boy, do I ever feel silly. I should have notice that immediately. Must be the head cold.

That being the case, you have the mod incorrect. You've cut and spliced the collector of Q7, not the base. See if that helps.
R.G.

In response to the questions in the forum - PCB Layout for Musical Effects is available from The Book Patch. Search "PCB Layout" and it ought to appear.

12StringStratMaker

Quote from: R.G.That being the case, you have the mod incorrect. You've cut and spliced the collector of Q7, not the base. See if that helps.

Wow, you were dead right.  And don't feel silly for not noticing, I feel like a tool for doing it backwards, but every transistor symbol shows the base as the middle leg of the symbol so I thought it was natural to assume that the middle leg of the actual transistor was the base too. Or at least this link said showed it was the middle...

http://www.americanmicrosemi.com/tutorials/bipolartransistor.htm

Oh well, thanks for sticking around to make this trivial mod doable for me.  You're a class act.

R.G.

Quoteevery transistor symbol shows the base as the middle leg of the symbol so I thought it was natural to assume that the middle leg of the actual transistor was the base too. Or at least this link said showed it was the middle...
They absolutely do.

I think you've put your finger on one of the stubborn, ongoing problems that all beginners have to get past.

The physical device is pinned out like the schematic symbol enough to make it seem like the pinout **ought** to be like the schemo, but that's merely coincidence. The hard part is realizing that is a coincidence, and getting in the habit of looking up pinout always.

I think people using Japanese and Euro style transistors may hit this realization earlier than folks in the USA because their transistors are commonly pinned ECB, not EBC like the majority of the easy-to-find 2N.... devices.

So - hack it and let me know how it works. Enquiring minds and all that.
R.G.

In response to the questions in the forum - PCB Layout for Musical Effects is available from The Book Patch. Search "PCB Layout" and it ought to appear.

12StringStratMaker

Well when I got it wired right, I drilled the hole for the switch, and hot glued the wires in place (after ensuring everything was working of course).  Sounds just like it did in stock mode and a great touch for playing in the modded mode.  
I put your drawing on a clearer schematic so if people want it, email me at ERASETHISPARTdh_eatit@yahoo.com or give me a place to post it.  Thanks again R.G.

Peter Snowberg

I love happy endings. :D

Thanks guys! 8)

I can picture this being a useful mod for more than just vibrato.
Eschew paradigm obfuscation