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That Diode (in the lower right hand corner) that you marked with a question mark is installed backwards. Instead of having negative volts on your control grids, those tubes are cooking with plus volts. Reverse the diode and check the 300 uf capacitor (C5) in the low voltage circuit (maybe that...

I am going to explain how the 12 volts is distributed between the two 6 volt tubes IF, your Palomar 300A (the one with the separate power supply) is running 6KD6's or 6lf6's then, you will find that the source voltage comes in pin 1 of the tube and goes out of pin 12, pin 1 of the second tube...

It looks like it was built yesterday and it has that "Elkin" looking cabinet. I cannot see where the tuning control for the first stage is located but, it was designed for radios from the 4 watt era. Expect about 500 watts out. . PS: If you wanna know more about it, take some more pics...

There is a seperate winding for V1 and V2 on the power transformer, it is a center-tapped 40 Volt AC winding. The driver tubes are wired in parallel, pins 1 and 12 are the filament connection and should have 20 volts on them. The RF input is supplied to the Cathode (Pin 2). Pins 5 and 9 are...

WHOA, I Think You Have A Problem! Maybe it just the lighting and / or the fact that you have a fan blowing on that first stage; those first 2 tubes look like they are on fire. The first two tubes should run the same color as the final tubes. Something looks wrong from here. Those first 2...

Please kill the CAPS LOCK key. I have constructed a few '813 boxes, one was control grid driven with separate positive screens volts and negative going voltage bias supply. Most "Homebrew 813 amps were grounded grid and just like an 500Z it required 30 -50 watts drive per tube to light those...

I hooked up amps and radios backwards more times than I care to admit but, what happens is that the relay clicks but, because there is no RF power going into the input stages, the amp does not put out power. Keying a 2510 into an amp one time cannot blow both the radio and the amp, you need to...

Back By Popular Demand For A Limited Engagement. My Icon is now on it's "Final Victory Tour", I retired it prematurely, your response brought it back!:thumbup: The Moderators are still out, there is no word on mandatory retirement so, It might be around for a while or might not.:confused...

Unfortunately, I am not from Australia, that is just a picture of of how *I* look when *I* bend over backwards to insert my head up my buttocks.:biggrin: .

Yes, it could be done but, think along different lines and come up with a better amplifier. The 811a tube was originally designed for audio use and it really wasn't for use at RF frequencies but, what do I know, the manufacturers use them all the time (but you don't see them operating above 30...

As in Butte, Montana I received a PM today requesting that I find another Avatar, is it really that ugly that it offends the sensibilities and dignity of the message board? .

In stand by, Ep (Plate voltage should be high and Ip should be low to zero) In Transmit, the Ep will dip a little while the Ip will increast at a higher rate.

Nailed it! .

Try turning the Mic gain down (if there is one) and see if the problem goes away, if possible try a different microphone. .

Find yourself a Workman PDC 5 SWR Meter and Matcher, put it in between your radio and the amplifier and use it to adjust the "SWR" (input tuning) into the amp. Turn the Matcher off when not using the amp. This is an external solution that is easily applied by appliance operators asking...

Find yourself a Workman PDC 5 SWR Meter and Matcher, put it in between your radio and the amplifier and use it to adjust the "SWR" (input tuning) into the amp. Turn the Matcher off when not using the amp. .

Just a dream for an inner city kid, I want a full sized 160 meter loop but, I am settling for 80 thru 10 operation only on a OCF Dipole. .

I wonder how much B+ is on those 8877's to claim 10 Grand PEP out of two of them? .

Commercial amps (which is what he seems to be trying to decide upon) are only designed to do so many watts and that's it; if the OP needs more "Headroom" then he has to move up to an "Export Model" with higher input/oouput rating or go Homebrew. .

If, your amp is working perfectly, you should only see the Screen Overload Indicator come on when you are loading it up heavly or if there is a problem in the screen circuit. If you suspect that the Screen Overload Indicator is not working properly (not lighting of even flickering) the the...