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Texas star 500v let out the smoke
- Thread starter The mechanic
- Start date
I was running amp on sideband and first key it smoked. Turned off and unfortunately no repair techs anywhere near me. Only thing I can make out on cap is 100v. This is right at the input coil. What do I need to check other than this and probability of bad transistors from fireworks?
Common failure cap. Needs to be replaced with a metal clad mica 91pf. A 100pf metal clad works too and easier to find. Better pic of the whole amp would help to diagnose the rest.
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I don’t see any “physical” damage to anything else. I’m nervous about the transistors simply because I really paid up for this amp a couple weeks ago. Here’s a picture hopefully you can zoom in and give me the expert opinion. Thanks guys
I did unsolder the cap that’s why the coax is not soldered in. If it’s as simple as trying a new cap could someone post a link to what to get. I really appreciate the responses. Used to have a local tech that was good on everything I took him. Sure do miss ol Mickey Mouse being around.
Thank you. Have one coming. Would you mind if I keep y’all updated?
Ok ordered and installed the cap. Turned amp on and relay keys, but 0 output on watt meter. Transistors are warming up on their own, and the large resistors on top of the transistors are getting hot on their own. Had to remove power wire to get it to quit heating I don’t have a clue what to check or do. The amp does not key on its own when turned on. Relay in amp keys with mic key. 0 watt output and is trying to self destruct with it turned on or off. Starts heating as soon as power wires are connected——-not my amp generic picture of resistors getting hot. All 8 above pills
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Yep. One or more of the pills has shorted internally. Had a few go that way over the years....... It likely failed when the cap went. Either the cap failing caused a pill to blow, or much more likely the pill failure caused the cap to blow.
What radio were you using to drive the amp? What was the SWR into and out of the amp before it blew? What kind of antenna?
FWIW I always hook up a dummy load when I am using a new amp for the first time. That way I know I'm keying into a perfect 50 ohm load with very very low SWR. If it works fine on the dummy load, then I'll go ahead and try it on an antenna.
Galaxy44 with a 3 watt dead key. Running an a99 with a 1.2 on channel 1 and a 1.4 on channel 40. —I went back out and checked a couple of things. There was a super small ball of crud I’m guessing from the cap that was between front board and rear board. Cleaned everything good and amp doesn’t get hot. Works but only making 55 watts. All pills are getting to about 85 degrees using a digital laser thermometer. Started at 44 degrees. Metal clad cap on one output transformer is getting to 140 degrees and other metal clad on second output transformer is getting to 88 degrees. Also r29 is gets to about 145. I have no parts available at all. Could r29 be causing the poor output power? Wouldn’t shorted pills either stay cold if completely dead or either get scorching hot? Thanks everyone