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Can a 1W resistor handle 50W for 7msec?

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normanstrong

Jan 1, 1970
0
John Robertson said:
Not an expert on instantaneous surges in resistors (you could ask my
daughter - she is in third year physics ;-) but I would suggest that
you consider using Flame-Proof resistors in this application. these
are resistors that open internally and do not burn up your board when
they fail...sometimes known as a fuse resistor....

John :-#)#

This is an entirely different situation. The maximum flux density is
fixed by the core material, and cannot be exceeded, no matter how much
current you feed through the coil.
 
D

Dana Myers

Jan 1, 1970
0
Roger said:
Check for wire wound resistors, they are most likely to be capable of a high
pulse of current.

I strongly suspect that a wire-wound resistor is totally
unsuitable for this RF application.

Dana
 
R

Roger Gt

Jan 1, 1970
0
Hi, good point. It should be Non Inductive winding of course. It has been
done!
I have two dummy loads I made this way. But they are Ni-Chrome in oil!
 
O

OK1SIP

Jan 1, 1970
0
Anyway, we had problems with the 7805 regulators shutting down from
overtemp. They were mounted on the PCB with a small heatsink.

Hi all,
overheating should not be neglected. In my professional life I
encountered a device made by a famous company, which had a 7805 on a
heatsink, a processor and several customer chips inside a tightly
closed plastic box. All was O.K. at power-up. I was called for service
after two days. The device was hot and really did not work. I let it
cool down and all was O.K. again - for next two days. I was forced to
remove the top cover of the box forever. The device has been working
for several years now.
Proper cooling seems to be a must.

BR from Ivan OK1SIP
 
R

Roger Conroy

Jan 1, 1970
0
The amount of time and energy expended on discussing this question by far
exceeds the cost and effort of just going ahead and frying a few of them in
a "hands-on", "live fire" destuctive test.

73
Roger
ZR3RC
 
B

Bill Turner

Jan 1, 1970
0
The amount of time and energy expended on discussing this question by far
exceeds the cost and effort of just going ahead and frying a few of them in
a "hands-on", "live fire" destuctive test.

_________________________________________________________

While the above statement is true in a literal sense, the time spent
discussing the issue is time well spent. Woe to any designer who learns
his craft by "live fire" testing.
 
U

Uns Lider

Jan 1, 1970
0
I worked for a small company that was owned by a conglomerate. The
conglomerate said that they'd never use any of our equipment that were
in a blue case. Which, since almost everything was in a blue case...

Anyway, we had problems with the 7805 regulators shutting down from
overtemp. They were mounted on the PCB with a small heatsink. So we
had to ECO them by adding a few inches of wire and bolting the 7805 to
the aluminum case, which soaked up plenty of heat. After that, no
more weird behavior.

It wasn't WG Security Products, was it? Doesn't sound like it. A while
back I got a used video quad that they had made, and the 7805 was mounted
like that. Also, the 7805 was blown.

-- uns
 
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