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I know this post is a little old, BUT.......... I have one of these ALS-500M amplifiers to use in mobile use for all bands. Manufacture date sticker inside is 02/2022 ....... Quality control sucks. It would not key when everything was connected. I had to troubleshoot the amplifier using...

It's a mobile amplifier. Good to run as 144inBama suggested above. Run it at 14 volts and it will run for years.

And that also gets back to my suggestion of checking the bias resistance and bias voltage as the first step. The issue would have shown up then at the beginning, and then followup with testing the transistors. Would have saved the OP a bunch of time. Bias checks is always my first step in...

Yessir, you would be correct, but notice that I said a proper license class does allow full legal power output of 1500 watts on 10 meter band. (General and Extra class)

Yes, but it's not illegal on 10 meters with proper license. and this antenna performs well on 10 meters.

Check the bias resistance first ......... Then check the bias voltage.........very quickly....... These are the two easiest things to do FIRST without changing out components and guessing.......

Check the bias resistance of the transistors first. Of course, with all DC power removed/unplugged from amplifier.

Well, nomad is right, if the amplifier heat sink is getting / staying hot, then that means the heat is being generated by the RF power transistors. It would be prudent to check the transistors bias resistance first, then do a quick check of the transistors bias voltage.

Definitely shorted somewhere. Just so you know, the on/off switch does not remove power to the amplifier. The on/off switch removes power from the relay and preamp function. A shorted D4, or C18, or C19 could cause this. Or a couple of other components.

It is easy to modify, and Solid state amps are produced the use a PTT keying line.

Sounds as if the keying transistor is shorted..... Whichever it is, it's an easy fix. Texas Star amplifiers are not complicated. Sometimes take a little time to pin point the issue, but I have repaired/rebuilt quite a lot of Texas Star amps. The TS 350 and 500 are the easiest to repair, if it's...

Hello Gatekeeper ....... Your ole friend, RANCH 55, just sayin' howdy ..... The Candy Blue 6 transistor amp still truckin. along just fine....... Later .......

LOL...... like that is suppose to mean something........ Still not legal anywhere, ....... "I can do what I want, whenever I want" Yep, could get interesting and funny with a "newbie" who knows everything.....

Bombardier said: Hello,do you happen to have the modifications for the Texas Star DX1600 by chance? Thanks if you do,,much appreciated. Is this the information you are asking about ? MODIFICATIONS CW Transmitter To AMP Conversion Texas Star DX1200 - DX1600 Documentation Project...

Check capacitors C29 & C38 for being open or extremely out of specification. ( I recently had a Texas Star 500 with an open C38 capacitor that exhibited the symptons you are indicating). Also check capacitor C45 for open or out of specification. As you may know, the output combiner resistor...

Okay, I did just exactly the procedure above as stated by "Handy Andy". I had considered this before. I set the Ammeter up inline with the power supply as above, no RF..... First, I checked the current as it was since I set the gate voltage at 4 vdc previously. The current was 1.752 amps at...

Sounds like the internal amplifier board bias voltage is not being set correctly. I had this same issue until I got some guidance from Handy Andy on setting the amplifier board bias voltage correctly. Once done correctly, I haven't had any more internal amplifier blow the transistors.

This board was built and assembled by Tom , W8JI, ctr engineering........