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ts 250 hdv
- Thread starter bginn
- Start date
Interesting question . . .
There are some guys here on this forum that can answer that. I will venture a guess or three, since I am new to understanding amp circuits and how they work.
I guess that the amp's keying transistor and relay would be the same. So would the receive amp.
The filtering capacitors on the board might be questionable, as a change in the main transistors might have different requirements to achieve the same result.
But I suspect that the final transistor biasing resistors are different and must be changed for 'AB1 biasing' for the 2879.
The combiner circuit might be a bit anemic for the extra power put to them and may also need to be modified with larger gauge wire. Perhaps larger ferrites too.
The main input power wires will also need to be changed out to a much heavier gauge for sure.
Since it is the variable power amp; I know that the variable control itself has been prone to failures. That is well-known.
There is one member on this forum called "TeasStarAmpRepair" that would know the answers for sure. He is a retired repair man for Texas Star. But as I said there are others who know amps fairly well, such as "mackmobile43" and a few others forum members do - I'm sure. More answers from those who do know - to follow . . .
There are some guys here on this forum that can answer that. I will venture a guess or three, since I am new to understanding amp circuits and how they work.
I guess that the amp's keying transistor and relay would be the same. So would the receive amp.
The filtering capacitors on the board might be questionable, as a change in the main transistors might have different requirements to achieve the same result.
But I suspect that the final transistor biasing resistors are different and must be changed for 'AB1 biasing' for the 2879.
The combiner circuit might be a bit anemic for the extra power put to them and may also need to be modified with larger gauge wire. Perhaps larger ferrites too.
The main input power wires will also need to be changed out to a much heavier gauge for sure.
Since it is the variable power amp; I know that the variable control itself has been prone to failures. That is well-known.
There is one member on this forum called "TeasStarAmpRepair" that would know the answers for sure. He is a retired repair man for Texas Star. But as I said there are others who know amps fairly well, such as "mackmobile43" and a few others forum members do - I'm sure. More answers from those who do know - to follow . . .
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Both Robb and 9c have answered your question. The 2879 is not a direct replacement for the 2290 pill. There is work needed in the circuit before and after prior to it being a direct replacement. Besides the extra few watts no one will be able to tell besides you looking at a watt meter.
http://www.worldwidedx.com/amplifiers/59097-texas-star-amp-repair-free-help.html
Troubleshooting
I was wrong about the bias resistors values if you read the TS troubleshooting guide. If you do end up replacing the stock transistors, I would replace those resistors at the same time. Perhaps with a better wattage rating and the more accurate carbon film type resistors. Just thinking out loud here . . .
Troubleshooting
I was wrong about the bias resistors values if you read the TS troubleshooting guide. If you do end up replacing the stock transistors, I would replace those resistors at the same time. Perhaps with a better wattage rating and the more accurate carbon film type resistors. Just thinking out loud here . . .
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Its not worth messing with part replacements for running the 2SC2879 transistors. I suggest just replacing them with new 2SC2290 transistors and keeping that linear amplifier stock and reliable. I will however tell you the biggest secrets and easy and cheap saftey precautions to keeping these amplifiers working and trouble free.
1. PUT A FAN ON THOSE HEAT SINKS heat is the biggest killer for electrical devices such as Transistors a $10.00 well worth it precaution.
2. With the 2SC2290 transistor keep the input drive power between 20 - 30 watts again WITH A FAN ON HEATSINK. Better off staying at 20 -25 watts for staying cleaner.
3. If running it in the house keepiing power supply voltage at 14.2 Volts at idle keeps the voltage from dropping to far which Ive seen some power supplies drop farther than others in voltage under a load.
4. Dont run more power that what it takes to get the job (contact) done. Remeber it only takes 100 wats to talk around the world on a good day and can be done with less if conditions are good. Theres no need to run wideopen pounding the piss out of the amplifier when its not even necessary.
I own a few Texas Stars and they are my favorite linear amplifiers as and Ive used them on 10 - 12 meters they are clean (if ran right) and are exremely reliable also if ran and treated right. Remember number one is keep in well ventilated area and keep cool with a fan and it will serve you a very longtime as mine all have.
1. PUT A FAN ON THOSE HEAT SINKS heat is the biggest killer for electrical devices such as Transistors a $10.00 well worth it precaution.
2. With the 2SC2290 transistor keep the input drive power between 20 - 30 watts again WITH A FAN ON HEATSINK. Better off staying at 20 -25 watts for staying cleaner.
3. If running it in the house keepiing power supply voltage at 14.2 Volts at idle keeps the voltage from dropping to far which Ive seen some power supplies drop farther than others in voltage under a load.
4. Dont run more power that what it takes to get the job (contact) done. Remeber it only takes 100 wats to talk around the world on a good day and can be done with less if conditions are good. Theres no need to run wideopen pounding the piss out of the amplifier when its not even necessary.
I own a few Texas Stars and they are my favorite linear amplifiers as and Ive used them on 10 - 12 meters they are clean (if ran right) and are exremely reliable also if ran and treated right. Remember number one is keep in well ventilated area and keep cool with a fan and it will serve you a very longtime as mine all have.
What Tony said...........plus, watch the input dead key on AM. Just because the 250 and 350 say HD on them it does not mean you can dead key 5-10 watts into them. All they need is 1.5-2 watts, 2.5 at the most. You want a 4 to 1 peak to carrier ratio. Too much dead key input makes them run very hot.
I had my amp done that way years ago and it still works great. I dont remember what all was done but it can be done. I use it for ssb on the base powering it with a 70 amp astron supply or for a driver for my bigger stuff. I was using it when talking to robb the other day.
The only difference between the 2 amps is the output finals and a direct swap is not an issue.
You will need to remove one wire turn in the input transformer.
I looked at the parts list on cbtricks and it all good.
So since you have to remove a wrap then it's not a DIRECT SWAP. Come om Mack why give out bad advice your smarter then that.
You will have to change 3 capacitors ,1 resistor and go to 1 turn on the input transformer http://www.cbtricks.com/Amp/txstar/dx250_dx350/graphics/ts_dx250_dx350_sch.gif
Well you'll have your soldering iron out so all you do is desolder one end of the winding in the input transformer, unwind one turn which is push the wire out the back side of the transformer, push it back through to the front side then cut wire leaving enough to resolder to the board and you're done.
There is a little more involvement to replacing the transistors but is straight forward and basically a DIRECT SWAP so I didn't mean to hurt your feeling by proving you wrong so please accept my apologies.
After checking the schematic, it isn't all that hard after all. I would still change out the bias resistors to the best that you can buy. This would ensure that the resistance stays stable and by using a resistor that has a higher wattage rating might help that. This is all conjecture; but it also stands to reason.
If one read the troubleshooting guide that I posted on this thread earlier, you can see that the damage done is most likely due to four main reasons. Too much heat/keying down too long, too much input power into the amp from the radio, feeding the amp too high voltage, and running the amp/antenna with a poor SWR.
If one read the troubleshooting guide that I posted on this thread earlier, you can see that the damage done is most likely due to four main reasons. Too much heat/keying down too long, too much input power into the amp from the radio, feeding the amp too high voltage, and running the amp/antenna with a poor SWR.
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