SB-200 Plate Voltage reading...

[John Farrington]

At 06:50 PM 05/04/2000 -0600, you wrote:
>Hi seeing as the meter is a 200uA movement , shouldn't the dropping
>string total 15 Megs instead of 14.1 Megs with the three 4.7 Meg
>resistors..?? Seems it would make the Voltage read about 7% too high...
>What are you SB-200 owners reading for Plate voltage with your stock
>meter strings...??? 73 de Jordan...

With just the 3 original carbon composition resistors the voltage drop
across each is too high for the value to remain stable over a long
period - they gradually change and cause an erroneous HV meter reading.
In place of R3 (three 4.7 meg), it's better to use a series string of
14 one-meg 1% film resistors 1/4 or 1/2 W, and replace R4 (to ground)
with a film 1% 15K 1/2 watt.  At 2400V the meter error will be trivial,
not worth the time that would be spent jiggering resistor values.

73

John Farrington  KE5ZB

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