Gary, If youre sure the other multimeter functions are working, then check the switch contacts, R214(1K) and R211 (4.7 ohms). There isnt much else that could go wrong. The grid current is measured by
Terry, your comment confuses me. Are you saying one or more of the following: (a) The coil of the input relay shows continuity when the relay is removed from the amplifier. (b) The relay is energized
Good advice, Steve. Markku should also check the calibration of his RF wattmeter. In my experience, these often become quite inaccurate at the low end of the HF spectrum, and always in the direction
Im dubious about using conducting grease for roller inductors. Generally, Ive used a thin coating of dielectric silicone grease for that kind of application. The purpose is to lubricate the roller co
A cool tube, Hsu, kind of a throwback to the 1960s, when homebrewers were running 3-1000Zs and grounded grid 4-1000As. This is a BIG old triode that I bet is a beauty to see lighted up with that nice
Theres no such thing as a ground loop?That is not correct, Jim! Of course, ground loops exist, along with substantial documentation on how to minimize them. I first encountered ground loops in grad s
Seems to me this problem may not be so troublesome. The dc resistance of the hot filament is 7.5V/51A=0.15 ohms. If the B- return is on one side of the filament, and if we assume the plate current is
I agree with your analysis and suggestions, Jim. One might mention that the switcher needs to have a floating 7.5V output, so it doesn't provide a ground reference for the filaments. Then the series
I've long wondered whether these speed-up circuits that pulse vacuum relay coils with an overvoltage also exacerbate contact bounce and possibly shorten the relay life. Intuitively that seems reasona
As Jim mentioned, in 2006 LDG briefly sold an autotuner designed to match input networks of cathode driven homebrew amplifiers. The model was the AT-100AMP, a similar design to the LDG LA100 autotune
I agree, thats got be a rectifier. Sent from my iPhone _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/listinfo/amps
For meter protection I also use back-to-back diodes across meter terminals. However, rather than using rectifier diodes, I use fast small signal diodes, like the 1N914a. Aside from responding more qu
When building or rebuilding HV power supply rectifier banks, I try to match the diodes to the circuit requirements. Fifty years ago my HV rectifier banks were an ugly snarl of diodes, resistors and c
Steve, are you talking about the fan or the blower? What does it sound like? When does it happen? 73, Jim w8zr Sent from my iPhone _______________________________________________ Amps mailing list Am
Flex transceivers have an interesting way of compensating for amplifiers with slow T/R switching. As with other transceivers, one sets a delay time to allow the amplifier relays to close. With Flex t
I received this interesting inquiry this week from Bob W4ZST about the history of grid and plate current monitoring in grounded grid amplifiers. Bob writes, /Who came up with the idea of metering gri
Hi all, As you probably know, commercial automatic vacuum tube amplifiers have been available for more than decade, but they are expensive; their pricetag adds about $2000 to the cost of a comparable
Hi gang Heres a response I made to a question from my friend Paul W9AC. Paul and I have known each other for years, and he is a very savvy, technically competent ham (as you probably already know). I
Hi Carl, Youve got lots of great stories. BTW we got our ticket the same year. I was wn0zke in Kansas City, upgraded to General, then lived as G5APG in England for a year, then to Ohio as w8kfl. Got
Good question, Jim. Yes, you will definitely need to remove the detent assembly. You also will need to gear down the stepper motor a bit. Heres why: Stepper motors are typically 1.8 degrees per step,