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It appears that now, my older Eimac 3-500Z tubes are the cause of the parasitic oscillations. I replaced the tubes with a newer set of 3-500ZG's and it seems to be working much better.? It seems the

If you're looking for a quality mechanical coaxial switch, with high-power capacity, low loss through UHF frequencies and very well-controlled (50 Ohm) impedance, the Bird CoaXwitch products are an

Reducing the HV can be done with a variac, lightbulb, heater elements, ?etc. but the filament primary needs to be isolated from the HV transformer primary.

Dow-Key transfer relay that can be placed anywhere and controlled from the operating position.

You want what's known as a transfer switch.? B&W made them and I see them for sale on eBay from time to time.? Here's the only one I found on a search just now, but it will do exactly what you need

Bob, Just so I understand fully, When you "key" the amp (no driving power) the plate current "goes to max"? On my L-4B the plate current max is? 1A !? If it is indeed MAX (1A) the power supply

Update: The TR7 includes a 500Hz. filter, a 1.8kHz. filter and a 6kHz. filter. Thanks, Robin Midgett K4IDC [email protected]> wrote:

Just throwing spaghetti against the wall here... Maybe your 7610 does not like the input circuit of the amp and is breaking into oscillation? Maybe you still have a relay issue. Hot switching can

Those units have F connectors...typically used in 75 ohm CATV circuits. Probably not suitable for 50 ohm radio circuits. Thanks, Robin Midgett K4IDC [email protected]> wrote:

Well, Alpha must have put that extra choke in there for a reason. :) This amp was built in 1977 and was still working. It was idle for many years before it saw light duty in the W0BJQ club shack until

Bob, I know you probably don't want to hear this, but have you considered 'exorcism'? Keep plugging away at it and I'm sure you'll figure it out. 73 de Steve, NR4M

Just got it back together after a full inspection.? Burnished the TR relay contacts, dirty but not arced. Now notice on low power CW mode, the Plate Current goes to max when I keyup and then takes

Down the page the specs say? +20 dbm.? Isn't that 100 milliwatts ?? Very low power . Ralph ku4pt

I have tried 2 different sets of tubes. Both were matched sets and seem to work perfect in my friends L4B.. Bob

This has been going on for a while, so please excuse me if I ask if you have tried different tubes. Steve Wedge, W1ES/4 Time flies like an arrow. Fruit flies like a banana. Sent with [Proton

I use multiple Alpha Delta 4-port and 2-port switches. Good isolation and have handled legal limit for over 17 years. Good up to 2 meters, but I only run 100 watts on 2 meters. Rob, NC0B

Yes, pse measure the uh when u have a chance.? ?BTW, that extra 15 uh is effectively out of the circuit.? Once you add the bypass caps at the base of the main plate choke, it's then game over.?

I have looked very closely at the tuning caps and cannot find any areas of arcing. It now seems that the problem is the TR relay is hanging up with some contact not releasing. I am going to remove it

Sounds to me like big vhf parasitic oscillation … to start with you need to get the hv supply power reduced for testing without destruction …. A very handy thing to have is a high power series

I don't recall the symptoms you are having, but have you checked the plate tuning cap for any signs of arcing? Bill N0CU [email protected]> wrote: