[Heathkit] Question on SB-200 meter circuit, replacement

[wb8jkr at juno.com]

 The plate current and grid current metering works
the same way, in the grid position the meter reads the
voltage drop across R15 the 1.5 ohm resistor, in the
plate current position the meters reads the voltage
drop acorss R12 the 1.0 ohm resistor, with R14 being
a series multiplier for the meter movement.

Mark  WB8JKR


On Thu, 23 Sep 2004 12:05:26 -0400 "Dennis Berry"
<dennisberry at worldnet.att.net> writes:
> I'm trying to understand the metering circuit on the SB-200 
> amplifier.  The meter I have seems to be off on the high voltage 
> reading, and I'm just trying to understand the circuit operation 
> better.  But, with me and understanding meter circuits and their 
> multiplier resistors, well it's like me and statistics.  My brain 
> sometimes just gets locked up and comes to an abrupt halt.
> 
> I've got a decent 200 ua meter that will fit in the existing space 
> fine, but it's internal resistance is 450 ohms.  So I need to 
> understand how the original circuit uses the resistors chosen for 
> grid, plate and HV in order to adjust the values for this meter.
> 
> If someone has done this and would care to pass on some knowledge, 
> that would be great.  You can contact me off list if you will, as I 
> may have some follow up questions as I work my way through this.
> 
> I know this is simple stuff, but it's just one of those areas where 
> it doesn't always make sense to me, and I'm sure with some good 
> clear descriptions it will make sense.
> 
> Thanks in advance to anyone who responds, 
> 
>     Dennis
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