Texas star 500v let out the smoke

[nomadradio]

Pull all the fuses. Put them back, one only at first. See if your receive-side current draw is there. If not, put in the next fuse and glance at the current meter. Should at least narrow down where to look. The other way is to unsolder the jumper wire feeding power to each two-transistor pc board, and seeing which one has receive-side current draw hooking them each back up one at a time.

The 10-ohm resistor from each transistor's base lead to ground is the most time-proven symptom of a blown RF transistor. A resistor that's visibly damaged points to the failed RF transistor. And lf all eight of them look good, that alone proves very little. A RF transistor can fail without releasing the "10-ohm smoke".

73

 

[Shadetree Mechanic]

If you found a ball of solider causing problems, it might be a good idea to pull the boards out to make sure there isn't one underneath. I have heard of that happening. If the transistors are all the same temperature, then I would say that they are all working. A dead one will be cold. So if they all work, but output is really low, I would look at the output tune capacitor.

 

[Xracerx13]

R29, a 100ohm 2W resistor, which is the final output combiner balance resistor and it is getting hot because there is an imbalance of power being put out from each 2 pill pair which runs to the combiner. The combiner L4 is the yellow torroid donut with magnetic wire wrapped around it that R29 connects in between. In short one board puts out more or less power than it should.
Which output transformer metal clad is 145* ?

 

[The mechanic]

R29, a 100ohm 2W resistor, which is the final output combiner balance resistor and it is getting hot because there is an imbalance of power being put out from each 2 pill pair which runs to the combiner. The combiner L4 is the yellow torroid donut with magnetic wire wrapped around it that R29 connects in between. In short one board puts out more or less power than it should.
Which output transformer metal clad is 145* ?

Front board

 

[The mechanic]

I give credit where credit is due. Shadetree mechanic, you were right. I caused the problem with the original repair of c45. When I soldered the coax back on it flowed under the board and shorted out. Thanks for the response bud.

The real thank you goes out to Super Lid. Walking me step by step through and giving me the courage to dive into something I would have never attempted without his guidance. Teaching me about bias voltage, checking transistors, and looking for the unexpected. Thank you. I’m afraid you’ll hear from me more as I put both boards, and all the transistors back in. You’re a great guy and “making” me go through with doing this I could never thank you enough.

Everyone’s response is much appreciated. I look forward to seeing other people’s posts as everyone I’ve dealt with has been encouraging and respectful. Thanks again to everyone and especially Super Lid. More than you know.