is there a reason the mosfet and CCs in the TSE are electrically in contact with the heat sink? Is it ok to insulate them from it or will that cause a problem. I am using a well over sized heat sink, so a little reduction in thermal transfer shouldn't be an issue. I just would rather not have the large heat sink at high voltage while I am adjusting bias and working inside the amp unless necessary.
As mentioned, you can insulate them with a pad. The 2SK3563 has an insulated case/mounting tab, although the 10M45S mounting tab is connected to the anode according to the data sheet.
How hot are they getting without pads ?
A Sil-Pad or better a Mica Pad will increase the temperature by about 0.5 Degrees C per Watt. If they are critically hot you might toast them. If they are warm to the touch then you will do no harm.
I assume that no crazy designer has used the heatsink as a current / signal path.
A Sil-Pad or better a Mica Pad will increase the temperature by about 0.5 Degrees C per Watt. If they are critically hot you might toast them. If they are warm to the touch then you will do no harm.
I assume that no crazy designer has used the heatsink as a current / signal path.
Ha, ha, but I can't touch them without the pads, they are at high voltage. I could after I turn it off, I suppose, but I haven't built it yet. I have very large heatsinks, pulled from a SS amp, so am not worried about it being too hot, just want to be sure that i am not missing something. I didn't think so, and I will insulate them just not to have to worry about the voltage on the heatsink. The thing is, with these large heatsinks, they are quite prominent and working on the operating amp seems fool hardy since just adjusting the bias might bring me uncomfortably close to a large high voltage chunk of aluminum.
If the heatsink forms no part of the circuit then you can but try.
See how hot they get.
Any transistor that gets above 75 Degrees after a few minutes is operating at its limits even on a heatsink.
I didn't use insulators in my amps because there are lost of dangerous things on that board and I believe that they should all be off limits to the user once the amp is completed.
Crazy designer....yes, but.....There are no electrical connections through the heat sinks, so an insulator can be added if the parts are well heat sunk. Many builders have pushed the board to voltages that I never thought of when I designed it. The "standard conditions" for a 300B 7 years ago was 360 to 375 volts at 60 to 80 mA. The Russian and Chinese tubes that I use will blow up at 400+ volts.
Higher voltages increase the dissipation in the mosfets and a insulating pad will increase the thermal resistance. If you have installed larger heat sinks and want to use an insulator, then go for it. If you built the board as designed and are running over 400 volts, it might not bee too good of an idea.
one time I got a big shot when I was checking a Sony ES serie receiver, I touched the heat sink and I did not see that my other hand was touching the chassis. The heat sink got really hot when it was at normal volume and when I increased the volume to 1 o'clock..uffff I could cook an egg on it!!!. I sold it to my friend and He also noticed and He told why I sold him a heater lol.
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