[Yaesu] FT-200 PA drive problem
ZL2AAA
[email protected]
2003年8月24日 09:48:42 +1200
The coupling cap between 12by7 and the grids of the 6146's was notorious for shorting and placing positive voltage on the grids
.It also appears that the value [100pf ??] is also critical 73's Morrie
----- Original Message -----
From: "Martin Sole" <[email protected]>
To: <[email protected]>
Sent: Saturday, August 23, 2003 3:08 PM
Subject: [Yaesu] FT-200 PA drive problem
Have an FT-200 on the bench that has been modified to take 6146's
instead of the 6JS6's. Problem is very little output on all bands.
Measuring with a scope across a 50 ohm load on the transverter low level
output I see about 850mV rms, say 14mW on 10m, decreasing at lower
frequencies because of the small value coupling cap no doubt. Is this
enough to drive the 6146's? I'm not sure if I need to be looking at the
PA or the driver circuit until I can figure out which is the problem.
The tubes check out fine in another rig, 6146's in a KWM-2A and the
12BY7A in a Drake T4XB. Any ideas?
73
Martin, HS0ZED
Moderator: Ray Brown, KB�STN
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