TB-303 Tempco Location

[Brassteacher]

I'm hoping someone with a real TB-303 can verify this for me. Most synths I've worked on have their tempco resistors thermally coupled to the expo converter, be it a chip or a transistor pair. In the copy of the TB-303 service manual I have, it shows the tempco running parallel to Q26 (2SC1583), but nothing is mentioned, or visible in the diagram, to indicate whether the resistor is simply board mounted, or on risers and coupled to the transistor with heatsink grease or a metal clip. It makes sense that it would be coupled to the transistor, but I'd like to know before I rig my x0x mainboard that way.

Oddly enough, my old Minitmoog (The "t" is not a typo) has one oscillator's tempco thermally coupled, while the other oscillator simply has its tempco board mounted about 10 millimeters away from the expo converter.

TIA!

[guest]

it just sits next to the transistor
to the best of my memory
i dont think its even off the board much

[phono]

i've got one open that im working on atm, i will see if i can take a pic for you.

[phono]

here's a couple of shots, as you can see its a single tempco (rather than two used in paralell in the x0x)

its just sitting right next to Q26 no paste or anything, just placed like a normal resistor

[Brassteacher]

Thanks Phono, those pics help a lot. It's kind of a "hybrid" of the two approaches I was thinking of. It's not far enough away that the temperature it reacts to is mainly caused by the change in current going through it, but neither is it securely coupled. However, it IS close enough to definitely pick up heat from the legs of the transistor.

I'm going to take a similar approach building out the x0x board I have. I'm going to mount the tempcos elevated, and one of them just barely touching the transistor body, and the other one just barely touching the transistor legs. That should give a good approximation of the arrangement in the pic. I guess the image scans in the TB-303 manual I have are not as clear as I thought, I had no idea the original TB-303 was a double-sided board!

Thanks again!