Howdy! I am thinking of a Texas Star DX500V and was wondering how the variable actually works. Does it just pad the input and drop the drive power? Thanx in advance!!
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Quick Texas Star ?
- Thread starter Greg T
- Start date
yes, the pot on the outside of the radio swamps more and more of the input signal to ground as you turn it down.
You could replace the pot with a fixed value resistor if you just wanted it set a certain way forever.
people tend to run them all the way up because this will help the pot itself last longer.
that pot is being asked to handle some current in this setup, and the pots used in these amps can/will eventually fail with enough abuse/use.
it really comes down to what your particular set up is.
if you have a radio that has a variable RF power knob on it, then it would be better to use that than the variable on the amp. why create all that power and then just heat the room up with it.
if you don't have a convenient way to turn the power into the amp down, and you need a way to adjust the amp's output, say, if you were driving something else with it, then maybe the variable is a good option for you.
personally, i would rather have the straight up DX500 and just use the radio to change the drive level.
LC
You could replace the pot with a fixed value resistor if you just wanted it set a certain way forever.
people tend to run them all the way up because this will help the pot itself last longer.
that pot is being asked to handle some current in this setup, and the pots used in these amps can/will eventually fail with enough abuse/use.
it really comes down to what your particular set up is.
if you have a radio that has a variable RF power knob on it, then it would be better to use that than the variable on the amp. why create all that power and then just heat the room up with it.
if you don't have a convenient way to turn the power into the amp down, and you need a way to adjust the amp's output, say, if you were driving something else with it, then maybe the variable is a good option for you.
personally, i would rather have the straight up DX500 and just use the radio to change the drive level.
LC
Thank you much for the rapid response! Well, I am running a Yaesu FT-990 which will match up perfectly with the DX500v on SSB because my variable RF out on that rig will adjust from 10 watts pep to 125 watts pep and maintain full 100% modulation. BUT, I can only vary between 10 watts and 30 watts dead key on AM. I was hoping to keep radio at 10 watt minimum and make up the difference with the variable on the amp. It will be a rare occasion I would use this on AM to begin with, but I just don't want to kill something IF I do.
EDIT: Or, possibly replace the variable with a much heavier piece?
Last edited:
wait, you want to run an FT-990 into a DX500?
on SSB?
so, the texas stars are unique beasts in that they are never on high power mode when the SSB delay button is pushed in.
that means that any time you want to talk on SSB you will be switching in some attenuation which will lower the output of the amp to less than 400 watts PEP (not sure exactly how much but that would depend on the input power).
Now i think i am understanding what you are asking about.
you see it as using the variable knob on the front of the amp to compensate for the fact that you are deadkeying 10 watts in to it.
is that right?
if so, you are thinking backwards.
think of it this way.
that amp is built to take a 4 watt deadkey and 20 watts of swing (AKA 20 watts PEP).
if you switch on the green button, or the yellow button, or both, you are incorporating some high wattage resistors that are taking some of that 4 watts and shunting it to ground. that is going to create heat inside the amp. Hey, no biggie, it's meant to handle that.
now if you were to deadkey 10 watts into that amp, then you can see that you would be working those same resistors more than twice as hard, and while your output will still be higher than if you deadkeyed 4 watts in, the amp is getting hot really quick because those poor resistors are working over time.
the same thing happens on SSB, but if you can get your PEP down to 10 watts, or even 20 watts, then the amp is made to handle that and it will work for you on SSB.
HOWEVER!
the question becomes why you would want to do that.
remember how the texas star amps SSB delay button also lowers the output?
that means that you have a radio that will do 100 watts PEP on its own and you want to turn it down to 20 watts PEP to do maybe 350, possibly 400 watts.
that 400 watts will gain you 1 additional S-unit in someone else's receiver over the 100 watts the Yaesu does on its own.
this is the part where people usually stop listening and just day F it, i want to run my amp!
to each their own.
point is, why complicate your life, deal with jumpers, power supplies, and more hassle just to gain 1 S unit?
hey, if that is what you need then go for it.
I don't know your situation.
either way, never deadkey more than 4 watts into that amp on AM regardless of what buttons are selected or where the variable pot is.
good luck with it.
LC
on SSB?
so, the texas stars are unique beasts in that they are never on high power mode when the SSB delay button is pushed in.
that means that any time you want to talk on SSB you will be switching in some attenuation which will lower the output of the amp to less than 400 watts PEP (not sure exactly how much but that would depend on the input power).
Now i think i am understanding what you are asking about.
you see it as using the variable knob on the front of the amp to compensate for the fact that you are deadkeying 10 watts in to it.
is that right?
if so, you are thinking backwards.
think of it this way.
that amp is built to take a 4 watt deadkey and 20 watts of swing (AKA 20 watts PEP).
if you switch on the green button, or the yellow button, or both, you are incorporating some high wattage resistors that are taking some of that 4 watts and shunting it to ground. that is going to create heat inside the amp. Hey, no biggie, it's meant to handle that.
now if you were to deadkey 10 watts into that amp, then you can see that you would be working those same resistors more than twice as hard, and while your output will still be higher than if you deadkeyed 4 watts in, the amp is getting hot really quick because those poor resistors are working over time.
the same thing happens on SSB, but if you can get your PEP down to 10 watts, or even 20 watts, then the amp is made to handle that and it will work for you on SSB.
HOWEVER!
the question becomes why you would want to do that.
remember how the texas star amps SSB delay button also lowers the output?
that means that you have a radio that will do 100 watts PEP on its own and you want to turn it down to 20 watts PEP to do maybe 350, possibly 400 watts.
that 400 watts will gain you 1 additional S-unit in someone else's receiver over the 100 watts the Yaesu does on its own.
this is the part where people usually stop listening and just day F it, i want to run my amp!
to each their own.
point is, why complicate your life, deal with jumpers, power supplies, and more hassle just to gain 1 S unit?
hey, if that is what you need then go for it.
I don't know your situation.
either way, never deadkey more than 4 watts into that amp on AM regardless of what buttons are selected or where the variable pot is.
good luck with it.
LC
That’s bad combination one wrong slip and t star could be toast. Just to easy to cook it by accident. That radio will be fine with just a good antenna. Just saying
I get it, fellers. That's why I asked. I've never run a TS amp before as I have always had tubes. But I've been out of the hobby for many years and just wanted to put a little more umph into it when the conditions roll in.I appreciate the advice and will reassess my my plan a bit. I don't really need huge power and I will rarely, if ever, use it on AM. Anyone have any suggestions on a better choice of boxes for the set up? It's just that I'm tired of tuning the tubes. Probably my age. It's a pain to have to re-tune every time I change frequencies. Base or mobile is irrelevant, I have a 100 amp PSU.
Thanx much!
GT
Thanx much!
GT
I ran a 500V with a 2950DX several years ago. Even with the SSB delay engaged, you can still make 500W. Which is the most you'll want to get out of it, by the way. With that radio though, look into something like an AL-811 amp. That was what I ran after the 2950/500V, with a Icom IC718. It's better suited for that radio, and with the ALC hooked up and set right, you'll have a nice, clean signal, solid 600W on SSB.
Yeah, I've been looking into the SB220 and the 811s but they're just too much money. I can't believe how much things have jumped in the last few years. Back in the day we used to sell 1.5kw boxes for $350 to $400 depending upon tube condition. I'm old, broken down and retired so those pieces are no longer within reach.
if you want a texas star amp go for the DX1600.
the radio you have will drive that amp wonderfully and give you a real boost in power when you need it.
LC
the radio you have will drive that amp wonderfully and give you a real boost in power when you need it.
LC
Agreed but find a good used one as it seems ts is using a Chinese Toshiba 2879 look alike transistors lately. Word on the street is make sure your vswr is no more than 1.3. That goes for hg or dei units. Do not volt them.
So far I have found that the knockoff Toshiba 2879"s in my Sweet Sixteen are performing just as well, if not somewhat better, as the HG's and DEI's ......
They have a date code of "6J" ........
I don't know about any other knockoffs ......
But as this point, I wouldn't be any more against them than the other two mentioned above.
I will say that these "6J" date coded knockoffs are internally much more robust than these other two. They appear more like the original Toshiba 2879"s. The tabs are attached internally much better than the other also.
They have a date code of "6J" ........
I don't know about any other knockoffs ......
But as this point, I wouldn't be any more against them than the other two mentioned above.
I will say that these "6J" date coded knockoffs are internally much more robust than these other two. They appear more like the original Toshiba 2879"s. The tabs are attached internally much better than the other also.
I'm pretty much open to any brand. I just want something that does what I want it to do. I've spoken with MANY box builders and it seems everyone is backed up and not taking new orders. I was kinda hoping to get something from Gatekeeper or BBI, but that ain't gonna happen. Gatekeeper (1883) hasn't even made a video in over a year. BBI said he's backed up for more than a year so no orders. Have spoken to a few others but they all say the same thing. I belong to a group on FB about linears and a guy was selling a Palomar 500 Elite. I messaged him and made a deal at $350.00 shipped. Well, it was a scam and I lost the $350.00 and FB will not help get it back. So, that cut my budget tremendously.
Wow that sucks. Too many fb scammers. I barely have an account anymore.
Yes as far as a fresh build goes, good luck. You might get away with having someone re-pill/repair/freshen up a clean used amp. The way things are atm you'll be hard pressed to find a decent working used amp. Let the Gov drop another stimulus check and you'll see even less. Ive been watching multiple classifieds for months and didnt see much that was decent and affordable. I got lucky a couple weeks ago and found what i was looking for but it took almost a year. Be patient and keep looking.
I also took a beating on Ebay. Long story that I won't bore you with, but I sold a Palomar 350Z, listed as NOT WORKING, FOR PARTS ONLY, and the guy took it, robbed the input switch from it, then complained to Ebay and they gave him his money back and I had to pay the return shipping on top of it. So, I have a 350Z that needs an input switch on the back but can't find anyone to fix it.
Had a little ts 250 no variable did a dad gum good job until I got greedy with power and KAbooom! But was awesome for what I been doing. Now I’m runnin barefoot until I find something else . But I hear the 500 is a monster but never owned one.
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