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Equivalent for 2SB857,2SB858 PNP

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mw7198

New Member
Thanks Sebi, I`ll pick one of those up and give it a try.

Thank you very much for your help

Justin
 

mw7198

New Member
Hello

I have installed the new components and the charger is working well, I have tested the current output and voltage and all is how it should be.... however my only concern is that while charging a 4.8v 1500Mha NiMh pack @ 1 amp the transistor gets up to about 80-90 degrees C ! is that too hot ? Looking at the data sheet it states the "junction temp" can be 150 degrees C....does this mean it can get up to 150 safely ?

Cheers

Justin
 

mozikluv

New Member
heatsinking

:D hello mw7198,

to put your mind at ease, put the pow. trans. on a bigger heatsink, bigger than the one you are using now. :wink:
 

mw7198

New Member
Thanks for the reply, The tran. in question is unfortunately not heatsinked !...and the case of the charger leaves very very little room to get one in !, I would really like to use a heatsink(I have quiet a few to choose from lying around) but the only way I can see using one is if I hang the tran.(and extend wires from the board to outside the case) outside the case and attatch a heatsink....which would look a little ugly... but I may have to do it ! ;)

Is 90 degrees C too hot for that type of device ?

Cheers

Justin
 

Sebi

Active Member
If the transistor work now without without heatsink, and only 90 degrees hot, for proper cooling quite enough about 15...20 quadratcentimeter aluminium plate. The totally closed case avoided.(drill a few 4mm holes both (opposite) sides)
On the 90deg running transistor can work, but this method use only the chinese manufacturer(Hi). In homebrew experience i never enable over 50...60deg. (i designed the devices for 99 years work...)
 

mozikluv

New Member
heatsinking

:lol: :lol: :lol: :lol: :lol: hello sebi,

thats the kind of work that i reeally luv, the kind that outlive the person who made it. :lol: :lol: :lol:
 
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