Curt I recently had a burned out fuse in my T4Xb and ended up changing a screen resistor and the meter resistors to get the meter to read properly. One of the finals (I was testing from used tubes was shorted) Put the original finals back in a a few resistors and it is working properly again. On the other hand it 'could' be just the fuse. Search the archives as I got some good help from several on the list also there are some pix and notes on my blog if you look back (it was sometime this past winter)
http://pgerhardt.blogspot.com Paul K3PG > > From: Curt <[email protected]> > > Subject: [Drakelist] T-4X filament fuse brunout and other strange > behavior > > To: [email protected] > > Date: Tuesday, April 27, 2010, 10:16 PM > > I had a surprising experience today > > when turned it, lights briefly came on then turned > > off. Turned out the filament fuse ( evidently the > > original ) had blown. Thinking maybe a tube filament > > had shorted, I checked current draw, 5 amps peak at turn on > > dropping to about 2 after warm-up. The fuse is an 8 > > amp fuse, and seem to recall fuses aren't quick to blow > > unless current is about 150% of the rating. > > > > So, does this just sound like a tired old fuse finally > > giving up, or is there something else to look into? > > > > Also, the plate current behavior seems more sensitive to > > drive than it used to be. On 40M, about 1/4 turn to go > > to 150 ma, then a very small amount more drive rotation > > causes the plate current to jump up to 250 ma. Efficiency > > doesn't seem as good as it once was either. 150ma used > > to show 40W on the tuner output meter, now about 25W. > > Bias cuurent set to 70 ma. PA tubes dying? Driver > > dying? both? > > Paul Gerhardt K3PG http://pgerhardt.blogspot.com QRP ARCI 6674 FP 274
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