Matt, You can select a resistor to drop the EM volts down some more. This would allow you to drop the beam current. However the instrument will work just fine at your values. As long as you can adjust the loop gain on the A7 to get 40 on the 2nd harmonic I'd just leave it as is. I have a 5061B that has an excellent tube. The minimum E.M. is 1200V and my beam current is around 48 (mod on). I just use it that way as it's a hassle to tear into just to change the beam current indication. Cheers, Corby

I found it amusing in the 5061 manual that they suggest using the 10Meg input resistance of a Valve Voltmeter as a current shunt to measure beam current Andy www.g4jnt.com On Wed, 7 Jun 2023 at 19:16, Corby Dawson via time-nuts < time-nuts@lists.febo.com> wrote: > Matt, > > You can select a resistor to drop the EM volts down some more. > > This would allow you to drop the beam current. > > However the instrument will work just fine at your values. > > As long as you can adjust the loop gain on the A7 to get 40 on the 2nd > harmonic I'd just leave it as is. > > I have a 5061B that has an excellent tube. The minimum E.M. is 1200V and > my beam current is around 48 (mod on). I just use it that way as it's a > hassle to tear into just to change the beam current indication. > > Cheers, > > Corby > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-leave@lists.febo.com >

Corby Dawson via time-nuts <time-nuts@lists.febo.com> writes: > You can select a resistor to drop the EM volts down some more. > > This would allow you to drop the beam current. > > However the instrument will work just fine at your values. > > As long as you can adjust the loop gain on the A7 to get 40 on the 2nd > harmonic I'd just leave it as is. > > I have a 5061B that has an excellent tube. The minimum E.M. is 1200V and > my beam current is around 48 (mod on). I just use it that way as it's a > hassle to tear into just to change the beam current indication. Thanks for the confirmation Corby. I can adjust the loop gain to get a 2nd harmonic reading of 40 at the lowest beam current setting. However, I performed the loop gain adjustment (5-220 in manual) to set the A8J1 phase detector test output to +/- 1.6V when the fine frequency adjust is set to 200 and 300 (normally 250, where the test output is 0). After doing this, the 2nd harmonic reading is >50. When I adjust the loop gain such that the 2nd harmonic is at 40, the phase det test output is much less than +/- 1.6V. I suppose maybe that +/-1.6V is only applicable with a 25nA beam current. Is that right? Should I neglect the phase det test output setting of 1.6V and just set the loop gain such that the 2nd harmonic reads 40? Matt