Need advice about Heatsinks

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PTL60

Member
2002-02-01 6:30 pm
If you guys remember, I had recently replaced the Transistors in my Creek OBH-11SE headphone amp. Now,these 4 transistors(BD140's),all had heatsinks. After I replaced the transistors I had a really hard time trying to put the heatsinks back on because the spacing on the board is very tight. So, I did not put the heatsinks back on. I've been using the amp for a few weeks now with no problems so far,and the amp dosen't seem to be getting any warmer than it did before I did this. So, my main concern is; Should I definitely put the heatsinks back on? Could I eventually have problems if I do not re-install the heatsinks? Thanks for any help.

Pete
 
The "amp" won't get any warmer or colder, with or without heatsinks (constant power). I'd be concerned that the ICs themselves, though, might be getting quite hot. Give it the finger test--if you can touch the BD140's for 10s, you probably aren't exceeding their safe area. (this is terrible science, I know, but it should work for you)

If the temperature is marginal you could make your own small 'flag' sinks out of metal sheet...even a modest increase in surface area helps dissipation some.
 
I'm not familiar with your circuitry, but when mounting heatsinks, it occasionally is easier to mount the transistors or other devices on the bottom of the board and bend them to the heatsink. Another technique is to attach the transistors to a bar that connects two or more devices, and then attach that bar to the heatsink. Finally, if the devices are scattered about your board and are not running too hot, you can simply attach a small piece of aluminum as a heatsink bonding it to the device with some silicon sealant (this isn't necessarily very pretty but it works).
 

PTL60

Member
2002-02-01 6:30 pm
Thanks for the replies. I forgot to say that this amp is a Class "A" circuit. The transistors are a TO-126 case. Also, I had tried to install push-on fin heatsinks on them,but there is not enough room on top of the board to get them on all 4 transistors without having to bend them in awkward positions. I still have the original heatsinks,so maybe I should just put them back on very carefully.
 
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