Does anybody use a heatsink at 2SJ109 in Aleph J. For me it looks like this device is getting pretty hot. In the closed case with ambient temperature inside 45C the transistor case temperature reaches 70C after 1 hour. I guess junction temperature is 75-80C. Or is it OK?
I'm using PCBs from Peter Daniel where 2SJ109 is pretty close to R5 which is getting quite hot.
Additionally what was the reason to connect R5 to negative rail? It could be connected to the ground with a value of 1.7K to get the same current through the zener but the power dissipation could be three timer lower at that resistor.
I'm using PCBs from Peter Daniel where 2SJ109 is pretty close to R5 which is getting quite hot.
Additionally what was the reason to connect R5 to negative rail? It could be connected to the ground with a value of 1.7K to get the same current through the zener but the power dissipation could be three timer lower at that resistor.
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Zen Mod,
There is the capacitor across the zener anyway.
I'll check the behavior in a simulation software.
Thanks.
There is the capacitor across the zener anyway.
I'll check the behavior in a simulation software.
Thanks.
I've changed R5 to 2.2k connected to the ground. As the result I got about 7C temperature drop on JFET case (from 70C to 63C in Peter Daniel's PCB) and C4 (before C4 could give a skin burn when touched). No any changes in the ripple of CCS and therefore in amplifier performance was discovered. So, highly recommended.
TO92 has typically 80~100°C/w junction to case, so you can calculate the junction temperature from power and case temperature.
I try to keep mine below 100°C for reliability reasons.
Patrick
I try to keep mine below 100°C for reliability reasons.
Patrick
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