Carl, You should adjust for the correct current. That said, the meter is at best difficult to read accurately.
The better way is to measure the voltage drop across the cathode resistors. R32 and R33 on my T4XB schematic. First see that they are both still 15 ohms, if not replace. Then measure the voltage across those resistors while adjusting the bias. According to ohms law, they should have about .5 volts to be at 33 ma. So 2 tubes each at 33 ma each is 66 ma, which is very close. The little bit off is still far more accurate than the error in reading the meter. 73, Ron WD8SBB --- On Sat, 2/11/12, Carl Maniscalco <[email protected]> wrote: > From: Carl Maniscalco <[email protected]> > Subject: [Drakelist] Setting the bias on a T-4X > To: [email protected] > Date: Saturday, February 11, 2012, 6:46 PM > Hello all-- > > I'm still new to the Drake world and just today got the T-4X > I've been restoring over the past few months working thanks > to one of Garey's CD-ROMs. I've got a question for the > experts, however: I've read the instructions and set the > bias control on my AC-4 so the plate amperes meter on the > T-4X reads .07A. However, when I check the the actual bias > voltage with a DMM, it's around -48 volts rather than the > expected -65 volts. If I adjust the voltage to -65 V, I get > about .02A on the meter. > > My question is, should I adjust the bias control for the > specified voltage or the specified amperage? > > --Carl Maniscalco, KJ6BSO > _______________________________________________ > Drakelist mailing list > [email protected] > http://mailman.zerobeat.net/mailman/listinfo/drakelist > _______________________________________________ Drakelist mailing list [email protected] http://mailman.zerobeat.net/mailman/listinfo/drakelist
