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previous: Aaron Flynt I just got finished putting togethe... -- 6/12/1999 2:05 AM

Re: D.I.Y. Amp Help Needed

6/12/1999 12:16 PM
Michael	Re: D.I.Y. Amp Help Needed The reason your plate voltage climbs when the tubes are gone is that there is little/no current flowing through the various resistors in your power supply circuit, thus there is no voltage drop. (Ohm's law, remember?) In order for the voltage to drop across a resistance, there must be current flowing. With no tubes to conduct current, no voltage drop. Don't worry about that - as long as your PS caps can take the voltage. As to your shunt measurements, I don't have enough info. I prefer the cathode resistor method, personally. Safer, and I'm measuring the entire tube current (plate + screen). In fact, for my DIY amps, I put a 1/8" jack in there for each tube so I can measure the idle current without removing the chassis.

6/12/1999 12:16 PM

Michael

Re: D.I.Y. Amp Help Needed

The reason your plate voltage climbs when the tubes are gone is that there is little/no current flowing through the various resistors in your power supply circuit, thus there is no voltage drop. (Ohm's law, remember?) In order for the voltage to drop across a resistance, there must be current flowing. With no tubes to conduct current, no voltage drop. Don't worry about that - as long as your PS caps can take the voltage. As to your shunt measurements, I don't have enough info. I prefer the cathode resistor method, personally. Safer, and I'm measuring the entire tube current (plate + screen). In fact, for my DIY amps, I put a 1/8" jack in there for each tube so I can measure the idle current without removing the chassis.