Thanks, Jim. I think something is amiss on the display board. All of the
metered parameters (both meters) are reading about 1/2 their correct values.
All the resistor values in the chain that are on the HV filter board check OK.
In my judgement, it’s unlikely that both meter movements would go south, and
a.ll of the metered parameters get “processed” on the display board. The output
power LED bargraph reads OK (compared to my Bird), but it does not share the
board components that are common to the other metered parameters. Using a
calibrated HV probe/meter, I confirmed that the plate voltage that initially
read 1600v on the multi-meter was actually 3200v. I was able to bring the meter
reading to 3100v using the R2 cal trimpot, and that was at the end of the
trimpot’s travel. Was also able to bring the metered FORWARD power value up to
the actual value. It was also initially reading 1/2 the actual value. Sure
seems like I’ve got something on the display board that's common to all
parameters that’s shunting the voltages. Haven’t yet removed the display board
for t-shooting, but it’s looking like that’s unavoidable.
Assuming I can locate and correct the 1/2 scale problem, I’ll still need to
know what values of voltage are at the input to the display board for
calibrating the plate current and grid current. Just tuning up by “peaking” the
output power, without knowing what the plate and grid currents actually are
makes me nervous. But so far, neither the amp or the 3-500’s have complained,
and the output signal is clean according to contacts with pan scopes.
73,
Allen—W7GIF
> On Mar 1, 2016, at 4:03 PM, Jim Brown <k9yc@audiosystemsgroup.com> wrote:
>
> On Tue,3/1/2016 2:55 PM, P C Andy Anderson wrote:
>> Allen, have never seen a procedure for calibrating the meters or I would be
>> glad to send it to you.
>
> Somewhere I found calibration instructions for meters in the Titan 425. It
> involves the use of a voltage source applied to certain test points, as I
> recall. It's been a long time. :)
>
> 73, Jim K9YC
>
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