using a seperate part to warm up a ge transistor

[ulysses]

hey guys

was wondering if something like this had been done before--

use a seperate part to warm up a ge transistor in the tone bender when its 10 degrees celcius..

ie, overpower a resistor or stick a mini light globe right next to the ge transistor??

ive seen resistrors get pretty hot, if a resistor is getting hot enough to warm up another part, what is its life expectancy?

cheers
ulysses

[soulsonic]

It seems to me that anything that would get hot enough would probably eat your battery up really quick. If there's enough room in the enclosure, maybe one of those chemical reaction hand warmer packets could be stuffed in there for the duration of the pedal's use. They certainly get warm.

[R.G.]

Congratulations. You have reinvented the on-PCB temperature servo.

For super-precision stuff it used to be common (well, common in super-precision stuff, anyway) to put a transistor or crystal in an on-PCB "oven" containing a resistor or transistor to make heat, and a temperature sensor. The whole mess was covered in a blanket of styrofoam or some such insulator. The temp sensor relayed the internal temperature to an outside control circuit which ran the heater until it was up to temperature. The temperature in the oven had to be higher than the air temp in the inside of the electronics enclosure to work, because it was a heat-only setup - it could not cool.

Today with peltier junctions, you could reasonably glue some peltier junctions and a temperature sensing thermistor to a Ge transistor and run it the other way, back down to maybe 5C-10C and get leakage to go down instead of up.

[Processaurus]

The $300 fuzz face makers should pay attention!  Sound like Jimi all year round.  But even Jimi had to wait for spring for that tone!

I actually love the idea, microprocessor controlled temperature for what was originally a 10 part fuzz pedal. 

Or, the cooling could be done by the Ge transistor heat synced to a beer can holder, with some indicator lights to tell you to finish it and get a fresh cold one out of the fridge.

[widdly]

They do that sort of thing in some VCO designs for synthesizers to make the tuning independent of temperature variations.  There is an example at EFM 3542 VCO http://www.ele4music.com/pdfs/3500_doc.pdf

[Pedal love]

  But even Jimi had to wait for spring for that tone!

The problem is if it gets too warm out, it also doesn't work.  

[ulysses]

thanks for the replies guys.

cheers
ulysses

[petemoore]

...have a radiator system, use hot [or cold] fluids run over the transistor, a small funnel with a transistor and drain tube *sealed to the bottom, and a bedpan to catch the hot coffee or cold lemonade that was used as thermo-control element.
  no really, you could take two, 1/2'' round, 2'' long rods with high thermal mass [like brass] insulate the top half for longer thermal retention, heated with coffee or Valves, cooled with ice, then in the special rubber fitting at the top of the 'cooler box' the specially placed transistor is mounted in.
  You'd want the transistor body bottom firmly mounted, epoxied in a hole in a metal 'cooler' box under the top of the enclosure, the grommet thing to hold the brass stuck in the enclosure top...the heat or cool of the thermally 'charged' brass plugs would get trapped in the air around the transistor cap and adjacent thermal mass and conductivity of the transistor refridgerator / heater box it's epoxied in.
  That and the Joe Gagan FF with a bias meter, you could get used to what temperatures the system would respond to.
  I think it was called the 'Nitro Burner' ...["Nitro-Cooler"..lol.
 

[analogmike]

Today with peltier junctions, you could reasonably glue some peltier junctions and a temperature sensing thermistor to a Ge transistor and run it the other way, back down to maybe 5C-10C and get leakage to go down instead of up.

I looked into solid state coolers (Peltier Junctions or heat pumps) this year for just that purpose, as our Peppermint Fuzz pedals started to sound bad when summer finally came.

They have a HOT SIDE that would need to be mounted to the pedal case or outside the case, to sink the heat, with the COLD SIDE in near the transistors. There are some REALLY CHEAP ones you can get from China, seem to be pull-outs or something... I decided not to use them. I thought I remembered some new IC chip that got cold without part of it getting hot but maybe I was imagining it. That type would be much better to use in a pedal if it existed.

I ended up using a 2nd bias trimpot inside the pedal and it works fine but needs to be readjusted every 10 degrees or more of delta T... and the transistors DO sound best at about 70 degrees no matter what you do with biasing.

Have fun!

[mac]

The external pot adjustment has the advantage of letting you to change the FF/TB tone at will.

mac