amps

[rustyc]

Looking at two texas star amps dx1200 and dx1600 what is the differance in pills the 1200 has 2290 pills and the 1600 has 2879

 

[mackmobile43]

2290 is a 60 watt device and the 2879 is a 90 watt device.

 

[wavrider]

http://www.worldwidedx.com/installation-station-setup/136626-texas-star-1200-1600-a.html

Same question a while back good thread with lots of info here.

 

[9C1Driver]

The 2290 is an 80 watt final, the 2879 is 120 watts per RF Parts.com

 

[AudioShockwav]

They have changed the data Sheets since the second generation of 2290/2879`s have come out.

They "now" rate them at 60 watts for the 2290 and 100 watts for the 2879.

This Page At RFParts.com http://rfparts.com/transistors_specs.html
Shows the old numbers At 80 and 120

This Page Shows the New numbers for the 2290 @ 60 watts
And the 2879 @ 100 watts if you click the links to the "new" spec sheets
http://rfparts.com/transistors_2SC.html#2221

The original 2290 was a 80 watt final, and the original 2879 were a 120 watt final.



The thing is, the data sheets reflect "min" specs at 12.5 volts in a test jig.
We all know they will exceed the minimum values in the data sheets, even more so at the nominal voltage put out by today's auto`s typically more like 13 to 14 volts with the engine running.

Texas star rates the DX 1200 at 900 watts out with 100 watts of drive
They rate the DX 1600 at 1200 watts out with 100 watts of drive.

Texas Star Export Feature Chart

I feel they are pushing it a little, but I disagree with the statement that a 1200 will only do 480 watts peak envelope power ... AVG... I will go for that but not PEP.
I think the terms pep and AVG get tossed out there together too much.
There IS a difference in the 2 terms.


73
Jeff

 

[psycho]

They have changed the data Sheets since the second generation of 2290/2879`s have come out.

They "now" rate them at 60 watts for the 2290 and 100 watts for the 2879.

This Page At RFParts.com Transistor Specifications at RF Parts Company
Shows the old numbers At 80 and 120

This Page Shows the New numbers for the 2290 @ 60 watts
And the 2879 @ 100 watts if you click the links to the "new" spec sheets
2SC Transistors at RF Parts Company

The original 2290 was a 80 watt final, and the original 2879 were a 120 watt final.



The thing is, the data sheets reflect "min" specs at 12.5 volts in a test jig.
We all know they will exceed the minimum values in the data sheets, even more so at the nominal voltage put out by today's auto`s typically more like 13 to 14 volts with the engine running.

Texas star rates the DX 1200 at 900 watts out with 100 watts of drive
They rate the DX 1600 at 1200 watts out with 100 watts of drive.

Texas Star Export Feature Chart

I feel they are pushing it a little, but I disagree with the statement that a 1200 will only do 480 watts peak envelope power ... AVG... I will go for that but not PEP.
I think the terms pep and AVG get tossed out there together too much.
There IS a difference in the 2 terms.


73
Jeff

I think 480 average for a 1200 is optimistic to say the least. 375-400 should be about right, never saw one do anymore than 800 watts peak. The "Hot Plate" is not all that hot, but it is a half step up from the 667. The 1200 is just 2 TS400s in one case plus the 400 is rated at 400 watts peak and they actually do just that.
It is pretty interesting that the newer 2879s are rated 20 watts less but have almost doubled in price. Remember Pearl Harbor!!!!!

 

[Eastside]

Better have at least a 150 amp alternator in your vehicle.

 

[mackmobile43]

The 2290 is an 80 watt final, the 2879 is 120 watts per RF Parts.com

You must be under driving yours. ^^ ab v c^^

 

[unit248]

I think the manufacturer specs emphasize the maximum output level at which you can maintain linear operation. The are a bunch of amateur radio transceivers that use a pair of 2SC2879s as finals (Kenwood TS-440, 450, 850, etc...), but those radios are all limited by design to 100 watts PEP. The ALC circuits are set to clamp the output at that point and no higher. By contrast, 11 meter "two pill" amps with the same transistors are often described as being good for 200 watts or more. (Granted, the ham rigs are almost certainly using a different bias strategy too.)

Now, can you actually drive them that hard? Well, maybe (with proper cooling), but once you push them outside their linear operating range, you will induce some distortion. It's not as bad as over-driving to the point where the positive modulation peaks flatten out (e.g. clipping), but the output will not be an entirely accurate representation of the input either, and that still equals distortion. It's very subtle (even with a scope it might not be very obvious), but the engineers that design the output stages for amateur rigs are more picky about this sort of thing, so their designs are more conservative.

-Bill

 

[AudioShockwav]

I agree with what you have said about Linear Operation , we all know that the guys that run these style of amps are not to concerned with IMD or Harmonics.

Now, can you actually drive them that hard? Well, maybe (with proper cooling)

Yes they can in fact, Tom, W8JI tested, documented, and validated that it is indeed "possible" to produce in excess of 250 watts from a single 2sc2879.
And you might be surprised that the Harmonic content is not as bad as you would assume.

Just out of curiousity I bolted up a single 2SC2879 in class C (zero bias) in a single ended amplifier with resonant transformer. Heatsink is massive and I used a soft copper gasket for better heat transfer, no grease.

On 5 MHz I can easily push it to 30 amps Ic at 18 volts and get almost 300 watts output. At about 30 amps my supply shuts down. I didn't filter the output beyond the resonant transformer but the 2nd harmonic was about 15 dB down and 3rd harmonic much less level than that. Harmonics were pretty much gone after the third. The harmonics clearly contribute less than 10% to the output measured.

The statement a single 2SC2879 can produce 250 watts is accurate, so long as linearity and long term reliability are not factors, and the 250 watts does not have to be "harmonics" or things that mislead power meters (although this could be true in some cases).

You can not rely on Data sheets for absolute ratings, often they are stated in Min ratings, such as Gain, or even Typical ratings because the MFG wants some room to wiggle.
They also do the test in a "test jig" with a supply voltage of 12.5 volts, again as has been already said, the avg auto now runs about 13.8 to 14 volts.
In the test that W8JI did above, the supply voltage was 18 volts.....so even though the transistor was rated by Toshiba to only be a 120 watt device, you can see what it was capable of, and how the Harmonic content was not "off the scale" even at the extreme level it was tested at.


Again, I will Quote W8JI:

It is common for people to think data sheet numbers are all hard limits, but a large amount of the data in sheets is NOT a hard limit.

A Zener diode would be a hard limit for voltage, but not for current or dissipation. The part might actually handle two or three times the rated current or dissipation before failing.

Resistors are the same. The resistance is absolute, but the dissipation or voltage rating (yes, they have voltage limits) is not. A 2 watt metal resistor might stand 5 watts for months or years before failing. A 2 watt resistor, like a carbon comp, might fail in a few thousand hours at 75% percent of rated dissipation. This is why standard resistors make about the worse fuse in the world, but some people think they are fuses that pop open with a modest overload.

Tubes and transistors are no exception. If you look at all the data sheets for the MRF150 you won't find it outputs 600 watts per transistor anywhere, but in pulse service it can. I built a medical device that ran over a kilowatt on two MRF-150's and they last years and years in the field.

A single 3-500Z can output several kW in low duty cycle operation, and can run 150% of rated anode current for years without accelerated failures, but the data sheet doesn't say it can do that.

73 Tom

Now, after all of this is said, do you want to run these transistors like this...no.
But the point I am trying to make here is the Mfg data sheets are not the end all of what a RF device can do.


73
Jeff

Note:
Tom, W8JI is the chief DESIGNER of amplifiers for Ameritron both solidstate and tube types. He also designed and has built very high powered amps for the ISM business.

 

[BOOTY MONSTER]

w8ji has also said ...................

OP
"Originally Posted by KB3HLK
On another forum, there is a guy claiming that a 2sc 2879 can produce 250 watts on the fundamental freq. at 18v for more than a few seconds. I told him he would blow it apart.... Isnt there a video showing this somewhere so I can shut this guy up? I dont have the time or money to make a jig and show him on the specan it not possible, let alone 2879s are $30 now."

reply frm w8ji

"Better be careful in arguments like that. Data sheets, especially poor ones without much data like the Toshiba sheet, and not absolute limits. All the data in the Toshiba sheet linked is for linear applications.

I haven't specifically operated a 2SC2879 at absolute maximum output, and the data sheet linked from this thread gives no indication what that might be in deep class C. It only lists linear AB service, but it is a 250W dissipation device. At 50% efficiency that is 250 watts output, and a deep class C operation might push that device to 60% or more efficiency.

I designed a medical RF device that ran two MRF-150's at 1200 watts output pulse in class C operation. They went to get them manufactured and Henry Radio told my client it would never work based on linear operation SSB data sheets. They came back to me complaining, and we tested and ran several units for MONTHS under all load conditions from short to open at full power. Hundreds of units were built and not a single unit failed even after several years of field use.

At Prime Instruments we used a very tiny FET the size of a 3N3904 to switch several amperes of pulse at 150 volts in assembly line device to charge meter movement magnets. It would never come close in linear duty, but in hard off-on switching it was fine.

Don't think a data sheet, especially one lacking so much data as the one linked and only listing SSB linear tests, is an absolute limit for all modes.

If you wanted to bet him based on it being linear, that would be one thing. If it was based on raw output with no regard to distortion or conduction angle (class) he could easily be correct.

73 Tom "

http://forums.qrz.com/showthread.php?248732-2sc2879-producing-250-watts-hahaha

post 1 and 5

the thread was posted in response to a thread that started here

http://www.worldwidedx.com/amplifiers/57320-hundreds-watts-per-2879-a.html

"Note:
Tom, W8JI is the chief DESIGNER of amplifiers for Ameritron both solidstate and tube types. He also designed and has built very high powered amps for the ISM business."

ameritron specs their als-500 series of amps as 500 watt amps . so they expect a clean 125 per 2879

http://www.ameritron.com/Product.php?productid=ALS-500M

my opinion is that since more than doubling power didn't let me talk farther (200 to 500) why stress the equipment and dirty the signal up when the only real world potentially positive effect is seeing a meter swing farther to the right .....

 

[AudioShockwav]

my opinion is that since more than doubling power didn't let me talk farther (200 to 500) why stress the equipment and dirty the signal up when the only real world potentially positive effect is seeing a meter swing farther to the right .....

Quite Correct.
My point was not disputing that the real world requires you to double the power to have a noticeable increase, it is that Data sheets are not the last word when it comes to output, and the "Assumption" that as voltage goes up and output goes up, is they suddenly become Spark gap generators.

I didn't filter the output beyond the resonant transformer but the 2nd harmonic was about 15 dB down and 3rd harmonic much less level than that. Harmonics were pretty much gone after the third. The harmonics clearly contribute less than 10% to the output measured.

ameritron specs their als-500 series of amps as 500 watt amps . so they expect a clean 125 per 2879

And we would all agree that Ameritron is held to a much higher standard than the Amps we are talking about, they are expected to live and meet standards that are non existent for what we are discussing, along with the fact that the Amp you are quoting about must do so under a much wider frequency range as well.

Bid difference in a Texas star amp and the ALS 500
You have been around long enough to know that.


73
Jeff

 

[psycho]

One of the guys in the tri county area has an Ameritron AL1500 and that is one outstanding piece. Pricey but even Booty would sport wood looking at that on a scope. :laugh: