Discussion in 'Amplitude Modulation' started by KD6CXW, Sep 1, 2019.
I need to spend more time reading and not being sleep deprived before working on any thing that could be fatal, the unit has protective circuits. hopefully I never need to replace the fuse it has a little bit of a price tag, although it is cheaper than the components its protecting . picked up protective choke and its plenty heavy to handle the transmitter .
WD4TC has one as well. Good friend.
Put Iron in , insulated bottom with 3/4 " plywood with a 1/4" silicon rubber mat on top, then sat the iron on it . Wiring was interesting, had three different schematics to go by, luckily Phil had posted one that fit mine. Have low voltage so put in oscillator and driver tubes. did not want to put in 4-400s until hi voltage is checked out. Not enough current to pull in k-2 for hi voltage, don't know if its because no crystal or no 4-400 or both.
Mine is getting a bath when it cools down. Then I am starting a top to bottom restoration. K3FEF told me I put her on the air too soon and that is probably why I have had all these problems. I will tell you that running with a ham band crystal and modifying the driver will cause issues. The designs for this are basically Tuned Grid Tuned Plate. TGTP are typically prone to oscillation. I had to use a spectrum scope (my Flex) to watch the outpoot. If I didn't tune her up just right, the sucker would spew garbage all over the band. You will want to add a neutralizing cap to stabilize your grid drive as you adjust TUNE and LOAD on the final. Finally, my advice is to forget crystal control and directly drive the grids with a plastic radio; about 15-20W for full outpoot. A friend is sending me a network to do this. Also waiting on new mod iron.
Bypassed under load relay for high voltage to come on, had strange voltages, narrowed down to plate transformer bad.pulled out some times 800 volts other times ? and will blow breaker or fuse.
now searching for replacement.
Contact W7TFO. He may have iron left over from his parts 707.
There is a guy who took over a transformer rewind service for hams but not sure if he is up and running yet.
Thanks Phil for the info, Dennis is hooking me up for the plate transformer.Did you get the info on directly drive the grids with a plastic radio?
Hope to have transformer in a week or so and want to start testing and do mods then.
CXW's iron will go out as soon as we are back from the land of power outages...Los Angeles!