Re: Power rating on ST-70 resistor
- From: Chris Hornbeck <chrishornbeckremovethis@xxxxxxx>
- Date: Thu, 13 Sep 2007 02:43:49 GMT
On Thu, 13 Sep 2007 02:06:32 +0000 (UTC), Leigh Orf
<orf@xxxxxxxxxxxxxxxxxxxxxx> wrote:
I'm not 100% sure changing the 15.6 jobber was an official part of any
of the upgrades I did; but I do recall both of them being far from 15.6
ohms, and knew that its value could be changed so long as the bias
voltage was set to match the change.
The value of this special resistor "seems" important, but its history
is now often lost. Dynakits are from an era long before three-
digit-accurate DVMs in every toolbox. But one accurate voltage
reference was available to everybody, a fresh battery.
No, there was only one kind. Arf.
This value of cathode resistor was chosen so that, at rated bias
of 100mA, the same voltage would appear across it as across a fresh
battery. Your meter didn't need to be accurate, only repeatable.
Cool, not?
Nowadays, separate resistors for each cathode are highly
recommended, along with separate bias trims. 10 ohms at 1/4
watt is idling dissipation (50mA) in this use, so a power
rating somewhat larger, but still small enough to provide
a fusing effect is needed. Call it half a watt or a watt.
Your work is done.
All good fortune,
Chris Hornbeck
.
- References:
- Power rating on ST-70 resistor
- From: Leigh Orf
- Re: Power rating on ST-70 resistor
- From: Sal Brisindi
- Re: Power rating on ST-70 resistor
- From: Peter Wieck
- Re: Power rating on ST-70 resistor
- From: Leigh Orf
- Power rating on ST-70 resistor
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