SB-200 Amp

[Walter or Margaret Korab]

Hello All,
           I'm installing all the mods recomended for the SB-200 and I wanted to check the
input impedance at each of the input coils. One suggestion was to temporarily install
a resistor that matches the input cathode impedance, to each of the cathodes to ground
on the 572B. This is of course a check without powering up. I have an mfj 259b, but I can't
make any sence out of what I'm finding.  The impedenace measurements are all
reactive, when Xc =Xl the frequencies are no where near the Fr should be and R is no
where near 50 ohms. I tried it with a cathode resistor of 50 ohms and without, both
measurements were the same. Tests were done with the tubes in place and holding in the
antenna relay. I know the accuracy is 2nd best without powering up, but if I can just get
close I could fine tune under power. Any Ideas?    Also, any ideas on the best way to
lower the filament voltage?  Should be 6.0V, I have 6.8V.
Thanks,
Walt,  w3fnz

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