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DEI Transistors

Tokin

The Man With No Shoes
Oct 31, 2019
1,697
3,065
273
55
SandBox
I will contact Mike at Galaxy to confirm this.
Again welcome to the forum.
If youre new to the transistor amp world again welcome and be very very careful as you first have lots to learn about not getting burned. Toshiba chinesium fakes have been around for about 10 years now and are popping up everywhere. Not saying theyre a bad transistor, they just aren't Toshibas. Texas star was using the 6j lot code fakes for about a year until they were called out on it. Thats when they went back to dei pills which are made by hg. Even being built by the same manufacturer the dei chips are inferior to the hg chips. Many reports of dei pills popping for no reason. Most builders have adopted hg as their primary transistor. I believe TS gets the dei pills cheaper in bulk than hg pills and just like the crappy wire and fuses thats why they use them.
Lots of junk "toshiba" amps popping up on Ebunk too. Hacked together and trying to get top dollar. Get close up pics so you can see every lot code as people are slapping in fakes with real to sell junk burned up boxes fast. If you still want to take the chance get pics on the insides and send them to a reliable builder/repair tech to confirm its not a giant pile of junk before bidding/buying.
As far as dei goes they get a vote of no confidence here.
 

Shockwave

Sr. Member
Sep 19, 2009
3,785
3,289
273
I think if you're talking in terms of "normal" usage this is correct. However, being that wires have an ampacity rating kinda messes the works. These amplifiers are actually starved because the power wires are much too light. I'm not saying the current is actually being used by the amp, but rather being lost in the wire and/or converted to heat. Once the amplifier is fed properly, the current is no longer lost in the journey.
Resistance in a wire doesn't cause current to be lost and converted into heat. It causes voltage to be dropped along the length of the wire. Depending upon the voltage dropped and the resistance of the wire, determines the amount of heat generated.

While there are some devices that can draw more current when voltage is reduced, such as induction motors, inverters and switch mode regulated power supplies, an RF amplifier does not exhibit this characteristic.

Here, a 50% reduction in voltage, automatically creates a 50% reduction in the current being drawn and results in an output that is only 25% of what it was before the voltage was reduced.

The only way for RF output power to increase while DC input power decreases, is if you were able to increase the efficiency of the output matching on the amplifier in question. Reducing the DC voltage to an RF amplifier is actually one of the most efficient ways to reduce its output power. This is because it does not alter the output impedance of the amplifier, like reducing the drive level would.
 

Greg T

945 (Jazz Singer) Upper Peninsula of Michigan
Sep 18, 2014
753
1,105
153
69
Escanaba, Michigan
Resistance in a wire doesn't cause current to be lost and converted into heat. It causes voltage to be dropped along the length of the wire. Depending upon the voltage dropped and the resistance of the wire, determines the amount of heat generated.

While there are some devices that can draw more current when voltage is reduced, such as induction motors, inverters and switch mode regulated power supplies, an RF amplifier does not exhibit this characteristic.

Here, a 50% reduction in voltage, automatically creates a 50% reduction in the current being drawn and results in an output that is only 25% of what it was before the voltage was reduced.

The only way for RF output power to increase while DC input power decreases, is if you were able to increase the efficiency of the output matching on the amplifier in question. Reducing the DC voltage to an RF amplifier is actually one of the most efficient ways to reduce its output power. This is because it does not alter the output impedance of the amplifier, like reducing the drive level would.

I am not an electrical scholar so I cannot argue the points intellectually. Being a mechanic and golf car technician for 50 years has taught me many things. I do know that if a wire is getting hot at the terminal, it is a bad connection and bad connection has high resistance. I also know that if you draw too much current thru a wire with too low ampacity it heats up. This is how electric heaters and incandescent light bulbs work.
Aside from that, I also know that my amplifier barely reached 470 or so watts of pep while drawing 60+ amps using the factory 12 ga wires and chinesium fuses with about 20ga wire ganging them. Powering each board with it's own 10ga wire directly to the power supply netted 650+ watts of pep and now only draws 40+ amps. Nothing else was changed. I can't make a comparo vid because I don't have a "before" , but I can make one of it running now, if you need to see it.
 
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Shockwave

Sr. Member
Sep 19, 2009
3,785
3,289
273
I am not an electrical scholar so I cannot argue the points intellectually. Being a mechanic and golf car technician for 50 years has taught me many things. I do know that if a wire is getting hot at the terminal, it is a bad connection and bad connection has high resistance. I also know that if you draw too much current thru a wire with too low ampacity it heats up. This is how electric heaters and incandescent light bulbs work.
Aside from that, I also know that my amplifier barely reached 470 or so watts of pep while drawing 60+ amps using the factory 12 ga wires and chinesium fuses with about 20ga wire ganging them. Powering each board with it's own 10ga wire directly to the power supply netted 650+ watts of pep and now only draws 40+ amps. Nothing else was changed. I can't make a comparo vid because I don't have a "before" , but I can make one of it running now, if you need to see it.
All I'm saying is if increasing the wire gauge to one with a lower resistance causes the current to drop, we need to be looking for another reason which doesn't defy ohm's law as the cause for this.

Consider things like every wire going in or out of the linear also acts as an antenna which can pick RF up and couple it back to the amplifier as feedback or an oscillation. Just moving a DC wire in reference to a coax cable that may have some common mode currents on it, can cause all types of unexpected changes.

You don't need to make a video because I'm not questioning your honesty here. I'm simply suggesting that the reduction you saw on your ammeter, has to be the result of something other than a reduction in resistance on the DC feed cable.
 

Greg T

945 (Jazz Singer) Upper Peninsula of Michigan
Sep 18, 2014
753
1,105
153
69
Escanaba, Michigan
All I'm saying is if increasing the wire gauge to one with a lower resistance causes the current to drop, we need to be looking for another reason which doesn't defy ohm's law as the cause for this.

Consider things like every wire going in or out of the linear also acts as an antenna which can pick RF up and couple it back to the amplifier as feedback or an oscillation. Just moving a DC wire in reference to a coax cable that may have some common mode currents on it, can cause all types of unexpected changes.

You don't need to make a video because I'm not questioning your honesty here. I'm simply suggesting that the reduction you saw on your ammeter, has to be the result of something other than a reduction in resistance on the DC feed cable.

Whatever it may be, Texas Star has been suffering from it for decades. There are countless videos on You Tube about it, which is where I got the idea to upgrade mine. Many builders have shown how inadequate the power system is in these amplifiers, and how the voltage stabilized, current draw dropped and output power increased when upgraded. What I'm saying is that the power wires are so inadequate in these amps that they are being starved.
 

Shockwave

Sr. Member
Sep 19, 2009
3,785
3,289
273
Again welcome to the forum.
If youre new to the transistor amp world again welcome and be very very careful as you first have lots to learn about not getting burned. Toshiba chinesium fakes have been around for about 10 years now and are popping up everywhere. Not saying theyre a bad transistor, they just aren't Toshibas. Texas star was using the 6j lot code fakes for about a year until they were called out on it. Thats when they went back to dei pills which are made by hg. Even being built by the same manufacturer the dei chips are inferior to the hg chips. Many reports of dei pills popping for no reason. Most builders have adopted hg as their primary transistor. I believe TS gets the dei pills cheaper in bulk than hg pills and just like the crappy wire and fuses thats why they use them.
Lots of junk "toshiba" amps popping up on Ebunk too. Hacked together and trying to get top dollar. Get close up pics so you can see every lot code as people are slapping in fakes with real to sell junk burned up boxes fast. If you still want to take the chance get pics on the insides and send them to a reliable builder/repair tech to confirm its not a giant pile of junk before bidding/buying.
As far as dei goes they get a vote of no confidence here.
DEI's lack of durability extends beyond their counterfeit Toshiba parts too. I've experimented with several of their 1200 watt RF transistors.What I can tell you is, take them outside of their specifications just a little bit and they go pop! While we should expect a part to fail when operated beyond its specifications, other reputable manufacturers incorporate a lot more headroom into their parts and that equals a lot more reliability.
 

TRASHYTRAM

OICU812
Jul 19, 2021
33
16
18
Again welcome to the forum.
Toshiba chinesium fakes have been around for about 10 years now and are popping up everywhere. Not saying theyre a bad transistor, they just aren't Toshibas. Texas star was using the 6j lot code fakes for about a year until they were called out on it.
I believe TS gets the dei pills cheaper in bulk than hg pills and just like the crappy wire and fuses thats why they use them.
Lots of junk "toshiba" amps popping up on Ebunk too.

Thanks for the interesting & Valuable information on this subject!
 

Shockwave

Sr. Member
Sep 19, 2009
3,785
3,289
273
Whatever it may be, Texas Star has been suffering from it for decades. There are countless videos on You Tube about it, which is where I got the idea to upgrade mine. Many builders have shown how inadequate the power system is in these amplifiers, and how the voltage stabilized, current draw dropped and output power increased when upgraded. What I'm saying is that the power wires are so inadequate in these amps that they are being starved.
I'm in 100% agreement here. There is no doubt that the wires and DC fuses being used create more voltage drop than desired. It certainly is a good idea to upgrade any wiring or fuse holders that get hot when in use. The fact that your amplifier is drawing less current now, is an indication that whatever problem you may have been having before, that caused more current with less output, is no longer present.

Efficiency went up without making changes in the output matching section of this amplifier. For that to happen, means that it is likely you had an oscillation present before this upgrade and that was ruining your efficiency. Once the oscillation is knocked out, all output power is on the fundamental frequency and efficiency increases.

One possibility may be the removal of all the extra wiring around the stock fuse holders. That also removed a path for RF to find its way back into the DC line.
 
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TRASHYTRAM

OICU812
Jul 19, 2021
33
16
18
Your a new member here, if you take a little time to read the forum, you will find that a lot of the guys here have been doing this radio stuff for a while.
Mike, from Texas Star has a account here , he could chime in any time he wants, in fact I am the one that sent him a e mail and suggested he join years back.
There is a very good user base here that have years of radio and amp experience, many work on and build equipment .

Welcome to the forum.

73
Jeff

Thanks, I'm sure all of this has happened & you are correct Mike is a great guy.
I guess it's all water over the dam now.
 

Greg T

945 (Jazz Singer) Upper Peninsula of Michigan
Sep 18, 2014
753
1,105
153
69
Escanaba, Michigan
I'm in 100% agreement here. There is no doubt that the wires and DC fuses being used create more voltage drop than desired. It certainly is a good idea to upgrade any wiring or fuse holders that get hot when in use. The fact that your amplifier is drawing less current now, is an indication that whatever problem you may have been having before, that caused more current with less output, is no longer present.

Efficiency went up without making changes in the output matching section of this amplifier. For that to happen, means that it is likely you had an oscillation present before this upgrade and that was ruining your efficiency. Once the oscillation is knocked out, all output power is on the fundamental frequency and efficiency increases.

One possibility may be the removal of all the extra wiring around the stock fuse holders. That also removed a path for RF to find its way back into the DC line.

If you've ever looked inside a TS you've seen the pathetic excuse they have for fusing. Two fuses, with a solid core piece of maybe 20ga wire tying them together, and a single 20ga solid core running from the fuses to each board. When I opened it up I just shook my head. I ripped it all out and soldered a stranded 10ga power wire to each board, and the same with the grounds, leaving the OEM ground strap between the boards intact. I now have two 10ga hots and two 10ga grounds coming from the amp, terminated via 175A anderson power pole. With NO other changes being made, the power jumped, the draw dropped. It was that simple. And I 'm still only driving it with 30W pep which should be perfectly safe. I am getting rave audio reviews whenever I'm DXing so I must not be anywhere near the saturation point.
 
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bevis

Member
Sep 28, 2020
65
23
18
56
I thought all I had to do was wrap the fuse in aluminum foil & that would solve the problem.

Come on man ( pedo-pres reference intended ) , you know that aluminum foil is only good to about 50 amps. You have to break out the copper tubing to run with the big dawgs. The Reynolds wrap stays on the porch or it gets the hose..
 
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144inBama

Sr. Member
Apr 22, 2020
619
1,059
153
53
Lower Alabama
View attachment 46527
Come on man ( pedo-pres reference intended ) , you know that aluminum foil is only good to about 50 amps. You have to break out the copper tubing to run with the big dawgs. The Reynolds wrap stays on the porch or it gets the hose..

aluminum foil is good for 250-ish. Here's the redneck fuse guide.....

e5b26071-5c68-496d-b6cf-e7aae83f2713.jpg
 

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