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Visual Electronics" 1KW AM tx info request...

A pair of 4-400s modulating a pair of 4-400s was very common in the 1KW world. Singer, Visual, CCA, McMartin, Bauer.... everyone built one. There's no magic in them, as long as the iron is good, you ought to be able to get it cookin'. I suspect the 4-400s are getting expensive and hard to find, but beyond that you should be able to get it running.
 
Nothing exotic about one of these. As long as iron is good, and the 4-400A tubes are OK, you should be golden. This one is not too much different from an old Bauer or CCA or McMartin.
 
Kent T said:
Nothing exotic about one of these. As long as iron is good, and the 4-400A tubes are OK, you should be golden. This one is not too much different from an old Bauer or CCA or McMartin.
Click to expand...

Careful about 4-400A tubes. Going back about 40 years (when last I worked with them) there were numerous brands. One of which (wish I could remember the name) had plates that looked like a length of black tubing that had been squashed into a vertical accordion shape. They always tended to run very hot on one side and were troublesomely short lived when run as modulators.
 
I have a couple or RCA 1r 's that run 4-400's and the only ones I have found to be reliable are the graphite plate Amperex branded tubes made in France. I get 18 to 24 months on them, but they are getting pretty salty, I think the last ones were about $350 each.
 
Amperex made some of the very best 4-400 tubes ever. Those tubes are long lived. EEV at one time also made good ones.
 
I have a RCA BTA 1R2 in backup service to the BE. When it was the main, the RF tubes lasted a long time and the modulators about 18 months at BEST.
 
4-400's in a Collins 20V with no filament adjustment available were an every 9 month expense. 4 of them topped a grand 15 years ago...I'd hate to see what they are now. You need to be in the 1% to operate one of these rigs.
 
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