Texas Star Sweet Sixteen (Older Model)

[Ranch55]

Well, it is going with the ASI 2879's …...
But it is not producing as much power output as I expected. It's as if the transistors are reaching saturation early …...
With 50 watts PEP input, max power output is about 750w output.
With 80 watts PEP input, max power output is about 800w output.
This is on 14.5 VDC …….
It is tuning okay with relatively low, acceptable VSWR on the input side …..
Still doing some analyzing ……..
At this point, I somewhat reluctant to install any of my HG's or Toshiba's …….

 

[999]

I wonder if the caps on the input and output transformers need different values or if the windings need to be changed?

 

[Shadetree Mechanic]

Maybe the output capacitor needs some tuning?

 

[Ranch55]

I have tuned the input capacitor to bring the input tuning down to a good swr input.
The output tuning is showing a VSWR with the stock capacitors at 1.3:1 , not bad.
I removed 1 turn from each input transformer with no change in output power.
I tried an experiment with another Texas Star DX 350V amplifier that is mine.
I removed the 2 Toshiba's from the 350, installed 2 new ASI's.
I had to retune the input capacitor slightly, output was very good already.
Same radio setup with both tests.
Maximum power output with 2 Toshiba's was 350 watts.
Maximum power output with 2 ASI's was 260 watts.

This tells me that the ASI 2SC2879 transistor just will not produce the same power output as the Toshiba 2SC2879 transistor.
Unless a different number of turns on the transformers would do it.
The current turns are Input=4turns ……. Output=6turns …….
But they are producing as per the spec. data sheet …...100 watts PEP per transistor

 

[ExitThirteen]

Sounds like it was a good thing I didn't buy any of the ASI 2879's. I'll stick with HG's or Toshibas.


~Cheers~

 

[2NC995]

Maximum power output with 2 ASI's was 260 watts.

Sad to hear. A DX350 with 2 Toshibas will pretty easily show 350 watts...or at least mine does.

Maybe we're learning why the ASIs never took off.

 

[TIN_CAN]

Sounds like it was a good thing I didn't buy any of the ASI 2879's. I'll stick with HG's or Toshibas.


~Cheers~

Speaking of HG's Carl built offers 2 versions of the HG 2sc2879 and HG 2sc2879C anyone else aware of these 150w versions? If they are decent mabey pick up a spare set for my sweet 16.

https://carlbuilt.net/shop?olsPage=products/hg-2sc2879

https://carlbuilt.net/shop?olsPage=products/hg-2sc2879-c

 

[Ranch55]

I was thinking about putting in a set of HG's to see what it does …..

 

[Ranch55]

Speaking of HG's Carl built offers 2 versions of the HG 2sc2879 and HG 2sc2879C anyone else aware of these 150w versions? /QUOTE]

Yes, I have seen them for sale on the ICA website.

 

[Ranch55]

But I will say that the ASI 2SC2879 transistor does seem to be as robust as the Toshiba.
It has the thicker ceramic insulator as the Toshiba, and seems to be able to take quite a bit of abuse and keep on going.
I just don't see the same power output as the Toshiba. But much tougher overall than the HG's and DEI's ……...
I am going to have to bite the bullet one of these days and pop the insulator off one of the used ones to look at the internals ……. I really want to know ….

 

[Ranch55]

OKAY , I did pop the lid on one of the ASI 2SC2879 transistors …….
It looks to be manufactured as robust and tough as the Toshiba 2879 transistors.

EXCEPT, the actual amplifying surface is only half as much as the Toshiba.
All the tabs are attached fully, as the Toshiba is. The ceramic base and cover is just as thick also.
When I saw the amplifying area, I could see why the ASI will not produce the same power as the Toshiba, or the HG, or the DEI ……..
But it will do what the spec. data sheet indicates...….. 100w ~ 125w max...….

The HG & DEI transistors have almost the same amount of amplifying area, but they are configured differently internally ….. And the ceramic base and cover are quite a bit thinner, with the tabs not being fully attached as the Toshiba and ASI.

My thoughts: the ASI 2SC2879 transistor is okay for a replacement, it will be just as tough as the Toshiba, just do not expect the same power output.
I don't like to try to get all I can out of my transistor amps, so I would be okay using them in one of mine, or someone's repair, as long as they are aware of the difference in power output to expect.
Probably won't find anymore of the ASI's anywhere anyway. What I got was NOS.

Now back to the Texas Star DX 1600 Sweet Sixteen:
I am now going to install some HG's I purchased from ICA Manufacturing and see what the amp will do with those.
But I have worked all the bugs and issues out of the amp.

 

[Ranch55]

I have stuck a fork in this Texas Star Sweet Sixteen, "Hot Plate" model .......
The HG's did not perform any better than the ASI's. The HG's were more aggravating to tune.
I did change the input and output tuning somewhat.
VSWR's are within acceptable operating range and maximum power output is up around 1100 watts with output VSWR of 1.2~1.3 .......
It is done, and I left the HG 2SC2879 transistors in it.

 

[2NC995]

I have stuck a fork in this Texas Star Sweet Sixteen, "Hot Plate" model .......
The HG's did not perform any better than the ASI's. The HG's were more aggravating to tune.
I did change the input and output tuning somewhat.
VSWR's are within acceptable operating range and maximum power output is up around 1100 watts with output VSWR of 1.2~1.3 .......
It is done, and I left the HG 2SC2879 transistors in it.

What’s it take for drive to get to 1100w?

Mine has DEIs I’ve never driven it beyond an output of about 900 watts, which shows about 100 amp draw...more than enough for me.

 

[Ranch55]

Just this minute checked this.
76 watt dead key into the amplifier produces 1003 watts output with VSWR @ 1.18 : 1 .....

 

[Tokin]

This is my neighbors Gatekeeper sweet 16 with HG 2879 transistors. I saw a 40w dk with a swing to 1800w pep on a PDC700 meter driving with his 2995dxcf base. Hes 15 miles north of me as the crow flies and hes loud, very clear but he says he bleeds a little. Ive never heard him bleed me at home but I guess folks closer to him have had problems. There was a small church across the street from him at one time and he mentioned problems there too breakah breakah hahaha.
He loves the amp but it isnt used daily.

Mr Dirty Whiteboy 521 Tampa/Moon lake.