Sunday, March 21, 2010

JBOT (1)

I am sure everybody recalls his first project; the planing, the component gathering, the drawing of the pcb, the smell of the solder and probably the smell of the first resistor explosion.... anyhow it's a very nice feeling. For a while I had those same feelings with this project, I bough some transistors and start to imagine in my mind the final look the component placement in the pcb. On to the tool shop and on with some drilling and grinding...
I choosed this linear amp for my hf-radio after considering some other designs because the transistors involved are relatively cheap, easy to find and most important, I liked the concept.... just a bunch of transistors.

Component layout on the soldering side:

The back side with and without the cooler:

Why did I placed the cooler and not some heatsink? Well I have a lot of coolers removed from computer power supply and none heatsink for the TO-39 case and most looks cool and looks like an appliance!
The cooler will be activated by temperature (of course!) using probably an 2n2222 working as temperature sensor because the case can be soldered to the 2n2218 transistor case (case on 2n2222 is collector so probably will have to work around on this or use another transistor in metal case).
Measured the consumption on the cooler and is around 140mA, printed specification is 230mA, so for a 5w amp I will have 1.7w consumption on cooling!

The project is based on this design:

Linked schematic:

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