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Another New Texas Star DX 500V
- Thread starter Ranch55
- Start date
I don’t understand what variable could exist beyond the transistors. Im sure they’re not individually tuning the amps since it’s all fixed value parts, but I would think the general tuning recipe would work more times unless the transistors were all over the map.
Was talking to Recon in messages last night and he seems to be having issues with his also.
Was talking to Recon in messages last night and he seems to be having issues with his also.
Refraining from any further opinion , subjective, objective, or sarcastic , I had just one experience with DEI power transistors. I will not have another.
Same here.
I have a pile of DEI transistors that I took out of TS amplifiers before the amps were ever used.
Shadetree Mechanic
Delaware Base Station 808
Not as good as the Toshiba's in my opinion.
But definitely better than DEI's ......
I wish you could say what other forums there are that are talking about TS 500's?
I remember when this subject came up there were some other guys talking about having SWR issues.
Copper was one.
There was also a long standing thread here, and over on Bennies forum talking about the chokes that Texas star was using getting overheated and causing SWR issues.
This did not seem to be a problem years ago.
Now it seems that using DEI Transistors has made the problem worse.
73
Jeff
Copper was one.
There was also a long standing thread here, and over on Bennies forum talking about the chokes that Texas star was using getting overheated and causing SWR issues.
This did not seem to be a problem years ago.
Now it seems that using DEI Transistors has made the problem worse.
73
Jeff
This is beginning to remind me of the problems with sweep tubes that arose when they were becoming obsolete.
The factories kept turning out the sweep tubes used in base linears in the 1980s after the TV factories had long since stopped buying them by the millions.
Manufacturing batch size came down.
So did quality.
The percentage of "dud" new tubes kept creeping up until they finally stopped making them altogether, and shut down the factories for good.
The very best, stoutest tubes like 6LQ6, 6KD6, 8950 and the like were made in the 70s when demand was high, and production quantities were highest.
Seems to me the Toshibas were famous for reliability more because they were made by the bazillions. Toshiba had their "cookie cutter" dialed in to the Nth degree.
The DEI and HG transistors are no doubt being made in smaller quantities than the Toshiba parts ever were. Bipolar RF transistors are becoming dinosaurs just like the sweep tubes were 35 or so years back.
This is not the only root of why they don't hold up as well. Got some pics I need to share next chance I get. Turns out the collector lead on the HG transistors is not anchored all that terribly well to the package. Gotta be gentle to it getting them installed. Makes removing them risky business.
Film at 11.
73
The factories kept turning out the sweep tubes used in base linears in the 1980s after the TV factories had long since stopped buying them by the millions.
Manufacturing batch size came down.
So did quality.
The percentage of "dud" new tubes kept creeping up until they finally stopped making them altogether, and shut down the factories for good.
The very best, stoutest tubes like 6LQ6, 6KD6, 8950 and the like were made in the 70s when demand was high, and production quantities were highest.
Seems to me the Toshibas were famous for reliability more because they were made by the bazillions. Toshiba had their "cookie cutter" dialed in to the Nth degree.
The DEI and HG transistors are no doubt being made in smaller quantities than the Toshiba parts ever were. Bipolar RF transistors are becoming dinosaurs just like the sweep tubes were 35 or so years back.
This is not the only root of why they don't hold up as well. Got some pics I need to share next chance I get. Turns out the collector lead on the HG transistors is not anchored all that terribly well to the package. Gotta be gentle to it getting them installed. Makes removing them risky business.
Film at 11.
73
That is what I also said in another post about the HG's being difficult to work with ...
I read somewhere that Texas Star was using matched sets of DEI now to improve things. IDK
thought they stopped making DEIs. It would seem we would be seeing factory TS boxes with HGs.
I been waiting for the swap over before buying.
thought they stopped making DEIs. It would seem we would be seeing factory TS boxes with HGs.
I been waiting for the swap over before buying.
Okay, made it around to taking care of this amplifier.
First thing, I connected it to transceiver to observe the performance.
1) .... High VSWR reading in transmit , 2.5 plus ....
2) .... One board getting significantly hotter than the other board. Indication of unbalance in output ....
3) .... Output combiner resistor getting extremely hot, also indicating unbalance in boards output .....
So, pulled the power transistors and pulled the boards.
1) .... The transistors were not matched as tested ....
2) .... Found a glob drip of solder under the input splitter. Appeared that it was touching the heat sink.
3) .... Found some kind of foreign conductive material under one of the collectors on the other board, and it was also touching the heat sink.
Took care of the two above issues and reinstalled the boards.
Replaced the output combiner resistor that was getting hot.
Installed 4 new RF Parts branded HG transistors ...... RFP 2SC2879 .......
Did not need to do any re-tuning as it was good.
The previous tech who had worked on it had already completed a very good power wire upgrade and the tuning capacitors he had installed were spot on.
14.0 vdc on the power supply ......
Dummy load VSWR was at 1.01 ~ 1.1 .........
On the antenna, VSWR was at 1.25 ~ 1.35 ......
16 watts (PEP) in produced 330 ~ 350 watts out .......
50 watts (PEP) in produced 450 ~ 475 watts out ......
All four transistors performing well and within 3 to 4 degrees of each other.
Output combiner resistor not getting hot any more, just warm .....
The customer is extremely happy now. He only pushes the amp with 16 ~ 20 watts PEP .......
His power supply is a 70a Astron set at 13.8vdc .......
I told him that it should last him years running it like that.
Mike tried to get the guys at Texas Star to simply place a insulator under the boards before assembly .
They never did.
Not to make an excuse for sloppy work.
I agree with that description.
Today I read a post that Texas Star is increasing the price on there amps 10% across the board.
They should step up quality control 25%.
73
Jeff