Texas Star DX-250 repair

[Greg T]

If you do put new transistors in it, don't apply any power before you have checked R8 for a proper resistance reading. It tends to blow out when transistors fail. When it does, the bias current on the RF transistors goes through the roof. Can blow out a new pair of RF transistors before you key it more than a few seconds.

http://www.cbtricks.com/Amp/txstar/dx250_dx350/graphics/ts_dx250_dx350_sch.pdf

You'll never guess how I learned about that pitfall.

73

Yes, Exactly what i would do. Check all the components dealing with input and transistor circuitry. I'm FAR from being a tech, but i can read a meter and can usually figure out what else would fail. This is a strange one, though. Having two transistors I would guess this amp likes about 6 to 10 pep watts of drive. The damned radio gave it a 15 watt carrier on SSB just prior to the death. When I pulled the cover I would have bet there were discolored resisters on the input side. I see nothing. NO signs of heat, anywhere. Maybe she blew so fast that it didn't have time to cook things. LOL