[Boatanchors] Please review & comment on my Heath Warrior HA-10 amplifier design changes

[Rick Poole WA1RKT]

From: "Gary Schafer" <garyschafer at largeriver.net>
Sent: Sunday, November 23, 2014 5:03:35 PM
>>
>> Moving the meter series resistor to the other side will give
>> you the same circuit that you now have but it will screw up
>> your meter when switched to plate current and plate voltage.

Good evening, Gary.

For the plate current, I'd have to reduce R11 from 10K to 9.61K... a relatively insignificant change, but in any case one that can easily be done.

As for the plate voltage circuit, I'm changing the bleeder and shunt resistors anyway.  It's nuts to have a 60K 100 watt (!!!) bleeder resistor there, generating all kinds of heat.  I have calculated several combinations of bleeder resistor and plate voltage meter shunt that are a LOT more reasonable in power dissipation, more like 5 to 10 watts, while still giving a reasonable capacitor discharge time.

>> It wouldn't hurt to also place diodes directly across the meter
>> for added protection of the meter. even though a lot of voltage
>> will appear across the meter it may help the meter survive.

A lot of voltage is right.  The meter would be asked to handle more than 10 times, something like 14 times, its rated current.  I can't imagine any meter surviving that.  A 390-ohm resistor in series with the meter, then back to back diodes (or maybe one diode... can the meter ever see a negative voltage?) across the resistor/meter series combination, and the most that the meter will be asked to handle is about 1.4 times its rated current.

I'm redrawing the schematic per the changes we all have discussed, and should have it up onto the web page in a day or two... gonna be tied up for much of tomorrow getting my furnace replaced ($$$$$$$$$-sigh) :-(

Rick WA1RKT