Cementing stuff together for tempco

Hi,

i am looking for some information on how to assemble a thermistor and transistors together in a way with good thermal contact.

the infiormation is probably on muff or electromusic, but i am a bit lost which keywords to search for and where to start looking.
also the muff wiki seems to be offline atm which doesn’t help.

thats why i thought i’d ask here for someone to point me in the right direction.

cheers Paul

I use JB Weld.

On my Synth.com Oscillator it looks like they just use some heatshrink around them.

Id use some 2 component Glue.
Glue the 2 Flat sides of the Transistors together and then the Resistor on Top, not as seen in you Pic. You want the Transistors as close as it can get so they have the same temperature, in the Pic above the Resistor is between the 2 Trannies so they could as well have totally different temperatures (in scales of compensation… ). Oh, and glue them before soldering for better alignment - you want as little Glue in there as possible. A good idea is isolating the whole stuff afterwards with some Heatshrinkzeugs™

I use some thermocouple adhesive. It forms a cement-like bond that is thermally conductive.

I’ve got a couple whip scars, Frank. :wink: I can get both oscillators to scale over 10 octaves and remain stable without having to retune. I’ve seen some people use a bit of aluminum between the transistors.

EDIT: Now I remember why I did it that way. As the pic above is a Soundlab Minisynth, I used the MFOS guide:“The tempco can go above a dual transistor package or between 2 discrete transistors.”

thanks a lot guys.

i thought it would be some strange construction involving heatsink paste and something pushing everything together mechanically…

i think i’ll socket the whole thing anyways becaue i don’t have matched transistors and the thermistor i found is a bit off. (3560ppm instead of 2500 i think)
then i’ll see how that tracks and maybe exchange some parts if i am not satisfied.

it’s for a 555cvo.

Oh, you have on, too. I was so Überschlau™ to order everything i had not in stock - expect the 100k PCB mount Pots…
BTW you need +3500ppm/°c

i think you don’t need pcb mount pots as the pcb is for assembling everything with wires.

the 2500 thing was a typo. i know it’s supposed to be +3500ppm
i got this one
i have no idea if it is the right one though.

did you get matched transistors?

I got 200 of them and make a nice evening Matching them…

:slight_smile:

i know who i’ll ask for matched ones, if my tracking is all over the place.

I found a Tempco for 555VCO from Australia. Looks more like a resistor, easier to fit that than the Mouser one?

Not so easy to find those.

I have a multimeter which has a place for transistors and so-called HFE function. I thought I just order a million transistors from Reichelt and try to match them myself…

There are a million interesting excerpts about matching transistors.
The problem with HFE measuring is the average Multimeter will just measure one Point of the characteristic of the Transistor while you need to match the whole thing.

On the other side Transistors from the same batch nowadays seem to be close enough or at least closer than you can measure with your 75€ Multimeter. You dont really believe it has 1% accuracy, dont you?

Of course it has.

No, I guess you could at least get two transistors which are not the furthest apart possible. So I hope it will help. Does somebody then sell perfectly matched transistors, by the way?

Just has to figure out a cheap way to get +/- 12 volts, as this VCO seems to need it. Suggestions?

Music From Outer Space does. Believe it’s $10 per match.

rosch wake up and match Trannies

Here

@Istran
What i was heading for was the possibility that modern Transistors could be closer than you can measure with your Equipment…

The conundrum of tranny matching…

The MOS Offer indludes the Tempco - not that bad.

you can buy matched pairs at musikding.de and banzaimusic.com
they’re quite pricey of course, i guess (or hope) they performed some time consuming procedures like described by Ian Fritz (can find details at electro-music.com)