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DX500 DEI to HG swap

loosecannon

loosecannon

Sr. Member
Mar 9, 2006
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Hi all,

im curious to know if anyone here has had to do this before and what they found.

im going to be swapping out some blown DEI's for HG's soon, and since all the schematics on CBT are based around the old toshiba pills, im not sure what the current models that have HG's have in them as far as tuning capacitor values, turns ratios and such.

even a photo that i can enlarge of a current model HG DX500 would be helpful.
or maybe there are current schematics out there and i just can't find them?

thanks for any input on this.
LC
 
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I am in the process of replacing the dei in my four pill with RFP brand hg. I have not powered it on yet because I was wondering the same thing. I assume people just drop them in and go, but I have to figure out what to look for if something goes wrong when I key up.
 


Ranch55 Well-Known Member




Joined:
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343
Ranch55 said: ↑
I have another Texas Star DX 500V amplifier in from a friend to take a look at. He purchased it new about 2 months ago.
It is experiencing high VSWR's on any antenna, but almost flat on a dummy load. This information is according to an experienced tech who has already had it.
He asked me to take a look at it.
My initial suspicion is the DEI transistors that it came with, based on the information he provided.
I won't have an opportunity to look at it for awhile yet.
Keep you posted.
Click to expand...
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.

#29 Ranch55, Jan 17, 2020
 
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Here is a video where BBI mentions that the output tune is different with the "painted" print transistors vs the ones that are laser printed that he said tuned very close to the Toshiba. Its in the beginning of the video where he shows the flats that the transistors come in. How to determine the output tuning I don't know.

 
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He also shows in the video to use an antenaylizer into the output coax connection to dial in the output tune. I know that the load is reflected thought the transformer, but does this method see the capacitor that is across the ferrite tubes on the transistor side? This gives us a clue but I don't think that we can know what makes the transistor itself happy unless it is putting out RF? I think this is the capacitor he was talking about, not the final output tune?
 
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Ranch55 said:


Ranch55 Well-Known Member




Joined:
Jan 17, 2016
Messages:
398
Likes Received:
343
Ranch55 said: ↑
I have another Texas Star DX 500V amplifier in from a friend to take a look at. He purchased it new about 2 months ago.
It is experiencing high VSWR's on any antenna, but almost flat on a dummy load. This information is according to an experienced tech who has already had it.
He asked me to take a look at it.
My initial suspicion is the DEI transistors that it came with, based on the information he provided.
I won't have an opportunity to look at it for awhile yet.
Keep you posted.
Click to expand...
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.

#29 Ranch55, Jan 17, 2020
Click to expand...
Can you share what value tuning capacitors were used
Ranch55 said:


Ranch55 Well-Known Member




Joined:
Jan 17, 2016
Messages:
398
Likes Received:
343
Ranch55 said: ↑
I have another Texas Star DX 500V amplifier in from a friend to take a look at. He purchased it new about 2 months ago.
It is experiencing high VSWR's on any antenna, but almost flat on a dummy load. This information is according to an experienced tech who has already had it.
He asked me to take a look at it.
My initial suspicion is the DEI transistors that it came with, based on the information he provided.
I won't have an opportunity to look at it for awhile yet.
Keep you posted.
Click to expand...
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.

#29 Ranch55, Jan 17, 2020
Click to expand...
Can you share the value of the tuning capacitors that were used please. Thank you
 
Ever since Toshiba Stopped production on the 2290 and 2689 transistors, several companies have offered "CLONES" of them. All I can say about whether they are as good as the original Toshibas is to open one up and look at the construction. Check the gold bonding wires as to number and quality. If the clones are the same, chances are they will perform almost as well as the original Toshibas. If not , . .

_ 399
 
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