Sujet : Re: dumping a lot of heat
De : alien (at) *nospam* comet.invalid (Jan Panteltje)
Groupes : sci.electronics.designDate : 09. Dec 2024, 07:36:13
Autres entêtes
Message-ID : <vj634u$10kd0$1@solani.org>
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User-Agent : NewsFleX-1.5.7.5 (Linux-5.15.32-v7l+)
On a sunny day (Sun, 08 Dec 2024 10:38:02 -0800) it happened john larkin
<
JL@gct.com> wrote in <
sfpblj1ckqupo92hh5vtvnbds9g9k655ii@4ax.com>:
On Sun, 8 Dec 2024 17:34:56 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
>
john larkin <JL@gct.com> wrote:
>
On Sun, 8 Dec 2024 16:36:25 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Jan Panteltje <alien@comet.invalid> wrote:
>
On a sunny day (Sun, 8 Dec 2024 13:33:39 +0000) it happened
liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
<1r490yz.1xraied16vto76N%liz@poppyrecords.invalid.invalid>:
john larkin <JL@gct.com> wrote:
>
[...]>RL
Tubes were awful. Still are.
>
The techniques for designing with them are quite different from
transistors and ICs, you have to think a different way; they aren't just
poor transistors, they have a different lifestyle altogether. They also
have some advantages over semiconductors:
>
1) Withstanding short term overloads without damage.
Thermal overloads depend on teh heatsink.
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Only slow overloads. Fast ones depend on the thermal time constant of
the bit being heated by the overload. Some time later the energy
reaches the heat sink but but then the damage is done.
>
I've just accidentally mixed up the anode and grid pins of one of the
triodes in an ECC91. It drew about 100 mA for a few seconds with no
damage. That's equivalent to mixing up the Base and Collector
connections on a transistor and subjecting the Base-Emitter junction to
about 10 times the rated maximum Collector current. How many
transistors would survive that, even with the biggest heatsink
available?
Mosfet data sheets usually have SOAR curves.
IXFH400N075T2 is rated for 1000 amps and 1000 watts (with astericks)
and 30 kilowatts for 25 uSec.
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Into the gate?
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Don't do that.
>
It's not hard to protect a mosfet from failure. The only way to
protect a tube from failure is to not use it.
>
A 1B3 makes a nice high-voltage capacitor, which is very reliable.
>
I have some beautiful tubes. 833 transmit jug. Some Blue Arcturus
things. A krytron. Some acorn and prox fuse tubes. A few gorgeous CRTs
and PMTs.
>
https://www.dropbox.com/scl/fo/m2ff4ty142v65omvmqf9k/ADvXu5nmmZ06w2hLulkZYL8?rlkey=z2tncdtgojshzogufp59xgxtw&dl=0
Yes I still use PMTs in my gamma spectrometers.
https://panteltje.nl/pub/PMT/PMT_1_img_2435.jpgno heater so efficient!
dumping a lot of heat
Re: dumping a lot of heat