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mats73 1st April 2003 05:32 AM

"Output" resistors(quick Q)?
Would there be any disadvantages in using 4 paralleled resistors with a value of 0,68 ohm instead from the standard 6 resistors with 1 ohm value(the 4 resistors would be rated at 5 Watt)?:scratch:

(It is for an Aleph 60)

mpopovics 1st April 2003 05:47 AM

You can use it, without any problem, if the paralelled value is the same.

mats73 1st April 2003 08:47 AM

Well, its not exactly the same, but I guess it is within the tolerances.

Just about 2 percent off and power rating 20 Watt instead of 18 so I guess it should be fine then.....

uli 1st April 2003 08:54 AM

Donīt forget that every Fet needs its own resistor!

Uli:devilr: :devilr: :devilr:

mats73 1st April 2003 10:18 AM

I donīt mean the resistors that are on the same boards as the Fets, but the resistors named R22- R27 on the "main" board of the Aleph 60.

uli 1st April 2003 10:27 AM

your choice
hi mats,
itīs up to you, even 2 0R33 parallel is ok as long as
their power handling ability is twice as high as the possible
power they have to handle.
10A x 1.65V = 16.5W -> each resistor should be 15W + to
be on the safe side.
You can calculate maximum current thru these resistors by
bias current divided by (1 - current gain of the CCS)
ALEPH2: 3 / (1 - 0.69) = 3 / 0.31 = 9.68 A.

Uli:nod: :nod: :nod:

jh6you 1st April 2003 11:34 AM


Originally posted by mats73
power rating 20 Watt

No reason to hesitate. :)


Nelson Pass 2nd April 2003 10:07 PM

It'll work fine. Tolerance need only meet about 10%.

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