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Texas star dx 500v
- Thread starter 66gto
- Start date
I already did that. I don't completely remove them i unsolder the base & collector. I have a Peak Atlas DCA55 they show O.K. like i posted. i checked base resistance and voltage they are spot on. All 4. Something else is throwing the Tune Off , I think a capacitor is the culpret. I changed 7 resistors on the rear board plus two capacitors, thats where the problem started rear board.
Shadetree Mechanic
Delaware Base Station 808
I have heard of people having problems with solder balls getting stuck under the boards. Might be worth a look to take the boards off. Might have one transistor with low gain? Might be something with the splitter giving one board more drive? The combiner problem is a balance of power problem.
Last edited:
66gto,
i hope this doesn't come across as mean, but my advice to you is to start reading some books on RF amplifiers and how they work instead of using the parts cannon.
every time you swap out parts you are introducing other variables into the equation.
any time you replace pills with anything other than exact drop-in replacements, you are going to have to re-tune the box.
also, sometimes solder connections on the top of the board are left unsoldered because they are soldered on the bottom side of the board. not saying this definitely happened to you, but ive seen it in a lot of texas star amps.
be sure to remove the PC boards from the amp and look for long component leads or solder blobs that could be causing issues.
because of the floating PC board design of texas star amps they are very prone to this type of issue.
good luck!
LC
i hope this doesn't come across as mean, but my advice to you is to start reading some books on RF amplifiers and how they work instead of using the parts cannon.
every time you swap out parts you are introducing other variables into the equation.
any time you replace pills with anything other than exact drop-in replacements, you are going to have to re-tune the box.
also, sometimes solder connections on the top of the board are left unsoldered because they are soldered on the bottom side of the board. not saying this definitely happened to you, but ive seen it in a lot of texas star amps.
be sure to remove the PC boards from the amp and look for long component leads or solder blobs that could be causing issues.
because of the floating PC board design of texas star amps they are very prone to this type of issue.
good luck!
LC
The resistor gets hot because one of the two push-pull transistor pairs is delivering less power than the other. If one pair shuts down altogether, that's a big imbalance. But if one pair puts out 2/3 the power of the other pair, that resistor still gets hot and smokes. Only when the both transistor pairs deliver equal power will the resistor stay cold.
Pinning down what causes the imbalance is a horse of another color. Finding which of the two pair is running weak can be done by unhooking one, then the other pair's input and output. Compare the wattage you get from the front pair and the rear pair. Keying it this way will deliver much less than half normal wattage, but there's a good chance one pair will be weaker on the wattmeter and point to where you should look next.
73
Pinning down what causes the imbalance is a horse of another color. Finding which of the two pair is running weak can be done by unhooking one, then the other pair's input and output. Compare the wattage you get from the front pair and the rear pair. Keying it this way will deliver much less than half normal wattage, but there's a good chance one pair will be weaker on the wattmeter and point to where you should look next.
73
I pulled the rear bord about ten days ago ,found nothing wrong. still looks like new. also before i replaced all 4 pills i checked them on my peak atlas DCA55 they all were within 4 points on the hfe. also i watch a lot of u-tube to see if i can get info about this problem. hard to find. ihave searched for this exact proble and came up with nothing. still searching.
Check capacitors C29 & C38 for being open or extremely out of specification. ( I recently had a Texas Star 500 with an open C38 capacitor that exhibited the symptons you are indicating).
Also check capacitor C45 for open or out of specification.
As you may know, the output combiner resistor (R29) getting hot is indicating an out of balance output between the two output transformers .......
Also check capacitor C45 for open or out of specification.
As you may know, the output combiner resistor (R29) getting hot is indicating an out of balance output between the two output transformers .......
Most texas star small transformers and large can be found pretty much made up on Ebay. As well as combiners. I have fat fingers so I just buy them and check them for correct tune to the transistor im using. the TS500-TX667 are the same except for the driver is a 2290 so you must use the appropriate one. I change the drivers to a 2879 so all of mine use the same. Hope this helps. Those DEI transistors are not worth making ear rings out of!!!
Greg T
WDX-945 (Jazz Singer) Upper Peninsula of Michigan
You'll never convince me of that. Over two years on mine putting out nearly 700 pep and running strong.
Greg T
WDX-945 (Jazz Singer) Upper Peninsula of Michigan
Just as a side note, Gregg at WEE (Stryker warranty Service) told me that Texas Star is officially out of business and liquidating their inventory. I'm sure their dealers are all getting first dibbs.
Shadetree Mechanic
Delaware Base Station 808
Man that's kind of a sad note, Texas star has been around a long time.
John told me once that Texas star is who acquired galaxy back in the day so it'll be odd if Galaxy continues.
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