[Heathkit] DX-60 Final Amplifier Tube Question

[Glen Zook]

No problems with the 6293.  It is basically a 6146A/8298 with a heavier plate.  The 6293 is rated at 1000 watts input when used in pulse service.

All that is required to use the 6883 and 6883A / 8032 in the SB-101 is to change the heater ("filament") connections on the final amplifier tubes from series to parallel.  I have modified a number of the Heath SB-Line transceivers to do this.  I definitely put a "sticker" on the final amplifier cage warning that the final amplifier tubes have been changed so that someone doesn't replace the tubes with the 6.3 volt tubes.
 
Glen, K9STH


Website:  http://k9sth.com


________________________________
 From: Drew P. <drewrailleur807 at yahoo.com>

Does the 6293 cause the same problems as the 6146B sometimes does?
And, is the 7212 more like the 6146/6146A or is it more like the 6146B?

I have an SB-101 having 6146B installed (I didn't do it).  Even with careful adjustment of neutralization using an RF voltmeter on the output, the final amplifier is still sometimes unstable when attempting to load into loads not having a very low SWR.  The final will sometimes oscillate when attempting to load into a 100 watt light bulb.  The 6146B's are "Penta", and show a date code for 1993.  The workmanship is poor - one tube is 1/4" shorter than the other, on one the envelope leans quite noticeably to one side; on one, the electrode structure appears to be crooked and not square to the mica.  These reputedly were made for Penta by Shuguang.

I lately has the rig loaded into a non-reactive 50 ohm dummy load, showing a mere 100 mA of plate current.  I turned my back for a minute, and when I looked to the radio again, the plate current was 400 mA, the output was way up, and one final tube plate was glowing an ominous orange, the other was dark.  Before I could get the rig shut down, the incandescent tube flashed over and blew the fuse in the HP-23 power supply.  I guess it's time for new final tubes.  I like the idea of installing 6883/6883A.