I'm building an amplifier with a separate power supply. The PS is a unit that sits on the floor. I wanted a small desktop amp and there's no room for a rack. In the power supply section, I have a 0.3
They are cheap. <snip> Is this a safe arrangement? I am thinking of adding another diode from B- to chassis in the RF section. I don't see how this could hurt, but it might help clamp the voltage in
I think my initial message was misleading. I think my brain was foggy, too. I was conflating two different designs that I was thinking about! The tube is a 4CX1000A, AB1 with a swamping resistor. The
This site http://www.granta.g4axx.com/Linear_design_notes.php3 mentions a 500 uh plate choke specified as RF Parts no. RFC-4L. They tested it and report that it has no series resonances between 1 and
The top of the swamping resistor is connected to the grid, but the bottom is bypassed for RF and connected to the bias and protective circuits. You are correct that it is to provide a load for the ex
Thank you. I think I will use an additional diode, or two as W6WRT suggested. Yes, I always use a 20-ohm glitch resistor, which I put in the amplifier. The power supply has a pair of 15A breakers. Th
Well, I just finished the cover for my power supply. Removed the clear plastic from the aluminum sheet, and it is beautiful -- except for the blue printing that indicates the alloy, etc. How do you g
I have several large pie-wound chokes, most around 1 mh or more. The thing about this one is that they found no series resonances below 100 mHz. It seemed to me that 500 uh would work well on 160m. I
I tried some of the XYL's nail polish remover, which contains acetone -- it works! Tomorrow I'll get some pure stuff at the hardware store. Thanks to everyone who suggested this. Well, I just finishe
I bought a 100 watt Weller W100P temperature-controlled iron (not a gun) from a company that sells stuff to stained glass hobbyists. I have never been sorry. The thermal mass of the large tip makes s
I am putting together the grid circuit for my ab1 4cx1000a amplifier. I am about to mount a Caddock 100 watt resistor on its heatsink, and I notice what looks like a square of tape on the mating surf
The 813 has a relatively high output capacity (14 pf) so it can be difficult to get a reasonable Q on 28 mHz with practical components. It helps to use a vacuum capacitor with a lower minimum as the
This is so true! I am now the local expert in fixing computer monitors that failed because the small capacitors in the switching supply that powers the backlighting have gone bad. If your monitor has
If the amplifier is class AB1, then it can use a swamped grid circuit. There should be no need for neutralization with a 50 or 200 ohm resistor as the swamping resistor. I have never seen these tubes
How big does the pressurized subchassis have to be to smooth out the airflow? My amp under construction (4cx1000a) has the socket in a 7x7x2 inch box with the blower pushing air into the side. Too sm
I'm proceeding with my AB1 4CX1000A amplifier. I've taken the advice of several reflector participants and used a pi-section lowpass filter design for the input circuit. It is very simple: a 120 pf t
I had a similar LF oscillation issue with my 813 grid-driven amplifier. I fixed it by replacing a grid RF choke with a resistor. If you can arrange the biasing so that you do not have an RF choke in
In a conventional 3.2 kV HV supply that I've built for my new amplifier, I bypassed each of the electrolytics with an 0.01 uf disc ceramic capacitor. My thought was that there will undoubtedly be RF
Well, if you grounded the B+ on the plate side of the RF choke, you could have heated the choke enough to make smoke without burning it out. It would probably be discolored in that case. Where did yo
It does sound like a parasitic of some kind. But why suddenly? Another possibility: something in the system is arcing. An arc might have a similar 'jumping' characteristic. What I would do at this po