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TEXAS STAR DX 500 won't power up
- Thread starter long night
- Start date
One more question. If keying transistor is bad will amp still key up or not? Will power not transfer to power transistors if keying transistor is bad?
The box will sit there like you're not keying at all. It will power on but continue to be in stand-by mode even while keying....basically like it's not even turned on.
I have ordered the transistor and capacitor for my texas star dx 500. Once I replace these is it safe to test the keying function without being hooked up to the radio just to check it?
Thanks again!!
For a proper dead key, key the radio/amp, modulate into it, note the max PEP reading, then adjust the radio's variable power if equipped, if not use the variable on the amp to 1/4 of your max PEP, i.e. 500 PEP, your dead key should be no more than 125....100ish is preferable. So....don't worry so much about the exact radio dead key, just adjust it to 100-125 watt amp output. I believe my DX500V needs 3/4-1 watt of drive for a 110 watt dead key.
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That's a pretty good indicator the transistors are bad, but you should be able to look at the 10 ohm tattle-tail resistors (R18, R19, R25, R26) and determine that prior to even keying. Can you post a clear picture of the inside of the amp?
If even one of those four looks different from the other three, it's a bad sign. Darkening at the middle of the part strongly suggests a failed RF power transistor.
73
I am an old disabled guy without a smart phone, so I am unable to post pictures. The power transistors look great for what it is worth. Upon very close examination of this amp there are two resistors close behind the controls that appear to be burnt on the ends. They are blue with gold bands on one end, two black bands and a red band on the other end. Could they be the problem? Also the relative meter and light which are both new fail to work now. Thanks for your expert help and advice.
Your diagram does not show the same band colors, but they are aprox. where R8 and R9 are in your diagram. They are smaller then R18 and R19, more the size of R8 and R9.
Looking again they are located exactly where R18 and R19 are so that must be them, even though the bands are not exactly the same mine have burnt ends. I will see what I can find to replace these if you think they are the problem? I have trouble getting to my station out in the shop so I should bring the amp inside to my computer to be more accurate. Please bear with this old man. Thank you Sir.