New Texas Star Sweet Sixteen 1600

[Ranch55]

Well, I went and picked up another brand new Texas Star Sweet Sixteen 1600 amplifier, that I don't really need. But the costs of these 1600's are really starting to go up and up. I just got it before the big price increases.
It has the Toshiba 2SC2879 transistors in it.
But I am pretty sure they are the "knock-off" Toshiba's.......
If they are like the last ones that came in another Sweet Sixteen I have, then they may be pretty good ones.
We'll see. If not, I do have some original, genuine Toshiba's that may go in.

 

[Ranch55]

Working on doing a full power wire upgrade on this new Sweet Sixteen.
The power transistors are the Toshiba's (knock-offs) same lot as the last new Sweet Sixteen, 6-J ........
I'm going to give them a go, as the last bunch are working pretty darn good.
Adding a cooling fan kit also. I have repositioned the fan thermal switch directly on top of the heat sink so as to get actual thermal switching. This is the third time I have performed this modification. Also added a switch to toggle between always on and thermal operation.

 

[Ranch55]

I completed the upgrades to this new Sweet Sixteen .....
The factory power wire to each board was 12ga. I upgraded each board to it's own 10ga. marine grade cable..
I added two 8ga. ground cables.
I added direct power wires with RF chokes to each output transformer.
I replaced the 4 filter capacitors (1000uf 16V) with new 2200uf 25V electolytics.
I added the 4 fan cooling fan kit. I purchased this amp bare, no cooling fans.
I moved the cooling fan thermal switch off the #2 PCB, and mounted it directly on top of the heat sink. This is the third Sweet Sixteen I have done this upgrade to and the amps operate much cooler.
I also added a switch to the front panel to toggle between thermal switch cooling or always on cooling.
All bias resistance checks are spot on. The initial bias voltage check to each board to also good.
I'll give this amplifier a good test on the bench in the next day or so to check if the input or output tuning capacitors need any tweaking.
I have a Palstar DL 2.5 HP dummy load I do all my amplifier testing and tuning with.
I also have some photos I'll share later.

 

[Dmans]

73
David

 

[Shockwave]

I completed the upgrades to this new Sweet Sixteen .....
The factory power wire to each board was 12ga. I upgraded each board to it's own 10ga. marine grade cable..
I added two 8ga. ground cables.
I added direct power wires with RF chokes to each output transformer.
I replaced the 4 filter capacitors (1000uf 16V) with new 2200uf 25V electolytics.
I added the 4 fan cooling fan kit. I purchased this amp bare, no cooling fans.
I moved the cooling fan thermal switch off the #2 PCB, and mounted it directly on top of the heat sink. This is the third Sweet Sixteen I have done this upgrade to and the amps operate much cooler.
I also added a switch to the front panel to toggle between thermal switch cooling or always on cooling.
All bias resistance checks are spot on. The initial bias voltage check to each board to also good.
I'll give this amplifier a good test on the bench in the next day or so to check if the input or output tuning capacitors need any tweaking.
I have a Palstar DL 2.5 HP dummy load I do all my amplifier testing and tuning with.
I also have some photos I'll share later.

Only thing I might add here are diodes in place of the low value 1/4 watt resistors they use in the bias voltage divider, to ground. They can be anything from 1N4001 to 1N4007. The stock bias circuit literally has ZERO voltage regulation, so that a 10% change in input voltage, causes a 10% change in bias voltage. That can be way more than a 10% change in bias current too. Most vehicle electrical systems are designed to fluctuate 10%, between when the engine is not running and full alternator output. That's the difference between 12.6 and 13.8 volts.

If you're not able to confirm bias current and don't want to adjust the value of the wire wound resistors to insure proper idling current, the best bet may be to just install these diodes in parallel with the existing resistors left in place. This will insure that replacing the resistor with the diode, does not allow more voltage to drop across the diode, than the stock resistor. It's safer to be a little under bias, rather than over and the diode will clamp that voltage to a safer level, if the input voltage is ever more than normal.

If you add diodes, you might as well place them on top of the output transistors to allow some thermal tracking. There should also be .01 uf ceramic disk caps across the diodes, to prevent them from rectifying any RF.