thomas organ wah?

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thomas organ wah?

Post by rockgod212 » Wed Mar 23, 2016 6:17 pm

so I just got a Thomas organ crybaby wah with the TDK inductor, it needs some TLC though. so a few questions.

1. it needs new jacks, so which ones?
2. are any of the resistor changes/ mods worth it?
3. are any capacitor changes/ certain brands worth it? i will keep the .01 cap. should i drop for some .22 tropical fish?
4. are the BC109's worth it.
5. is it worth it to re-wire it with better wire?

it was working briefly when I got it, so it did sound good through my 2203's. it could just use some TLC updates. just curious before I start tinkering away.
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Re: thomas organ wah?

Post by Haze13 » Sat Apr 02, 2016 2:14 am

If you need a good jacks, than use Amphenol or Neutrik. ~1.5$ a piece.
Resistors are for your taste. Can't comment on that. Play and listen for your self:) The circuit is very simple, and there is only 2-3 transitors that you can play with. Input - 68k, 1.5k (feedback), emitter resistor of input transistor and a 33k the 'q' transistor. Use a potentiometer for every one, adjust for the taste and replace with a resistor.

Electrolytics need to be changed, they are old and dried out.

I don't have tropical fish caps, but I've A/B-ed different caps, and russian PIO caps are were among the best. Better than a WIMA FKP2 audio grade... There are Bees Wax Caps, but they are like a 300$ for a piece and with a size of a small bucket, and I really don't know for whom they are :)
Tropical fish caps are Mylar type caps, so there are many caps of that type and you don't have to pay extra $$ for the mojo...
There is a lot of nonsense behind this subject, so it will be better if you will stay away from that. There is of course physics in there, and there are differences between the caps, mostly because of the dielectric, but they are small and you can hear it only under certain conditions.

BC109 are not worth it... Well if you have them you can use them, no Black Magic in them. The BC549-s are their replacement and very cheap. Just pay attention to Beta (Hfe) it should be around 500. Now there is a difference! I've compared 280 hfe vs 500 hfe . In other words they have not the same amplification. More than 500 are not worth it, just to much I think...
BC's have the gradation - A, B and C. The last one are 350-700 Hfe... Look for these.
There are 2sc2240 or 2sc1815 with different pin-out (Japan transistors). Gradation - Gr and Bl... Bl's are same as "C" - 350-700 Hfe. Long story sort - Use AUDIO transistors, look at their datasheets. Not because of the WORD but the input capacitance of the semiconductor. Lower the capacitance the better. And one more thing - THEY ARE CHEAP!!! There is no way that one of those will cost you more than 0.5$... Just look for the Beta, and application it was made for.

Wires... If it's made of copper leave it as it is.

For THEE POT I bought a Joe Gagan for the good sweep... love it!

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