President AR144 making no more than 5 watts?

[doffo]

Hello,

The President AR144 I got in a couple weeks ago seemed to be doing ok, but I realized that something wasnt right. Sure enough, the radio is refusing to do more than 5 watts, maybe 6ish watts no matter what mode. AM and SSB the radio wont go passed that. Driver and final Bias were set to 30/50. I am wondering if possibly the final is shot? The reason being is that when I was going to set the AM carrier, it shot up passed 10+ watts when you keyed up, and adjusting it did nothing. That is when I found a very hot transistor near the back. I believe the part was a C711. I replaced it with a C945. Now I could set the AM carrier and thought everything was ok. Even if the final is bad, would it still product any power output?

Any help is always appreciated. Thanks.
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After trying it again, what is happening is that you basically have to yell into the mic to get it near 10 watts, and thats with the ALC fully opened and the mic gain all the way clockwise. If you talk the normal 4 inches from the mic, it barely modulates a couple watts on SSB. On my Cobra 146 GTL, you dont even have to talk loud and she works fantastic and easily does 10 watts+.

 

[nomadradio]

Not to put too fine a point on it, but does the final transistor have a type number meant for sideband radios? Or did someone cheap out and substitute one meant for AM-only radios?

Worth checking.

73

 

[doffo]

Not to put too fine a point on it, but does the final transistor have a type number meant for sideband radios? Or did someone cheap out and substitute one meant for AM-only radios?

Worth checking.

73

The radio looks to of never been serviced, but just to be sure, it is a Mitsubishi 1969 final.

 

[doffo]

For fun I did replace the final since I was going to change out that ceramic piece behind it, and same results as before. Least I do have an original Mitsubishi 1969 final ill just save for another radio. PA mode is loud and clear.

 

[doffo]

I think the mystery is sorta solved.

For whatever reason, it mighta been the potentiometer to blaim. The other radios with similar boards don't even have a mic gain adjustment, and its basically "jumpered" under the board like my Cobra 146 GTL is and the very last Sears Roadtalker SSB mobile radio. I did just that, and now it seems to be ok and actually putting out 10 watts without me having to yell into the mic.

Now the issue is the audio is coming in a little too hot, and the ALC adjustment almost has the smallest window before its letting all the audio go through and going up to 10 watts. Before even with the mic gain attached, it too also was the same where it had little to no window fully clockwise, and backing it down just a tiny bit made it so you really had to yell in it. What can I check along the way to be sure there isnt a capacitor maybe needing a different value? I was tempted to compare both boards of the Cobra 146 GTL and follow things to see if cap values or resistor values changed.

Here is the picture for reference. (Both the top side 3 original wired that I desoldered), and the little jumper after the fact.