Realistic TRC 457 heats up, drifts, un adjustable

[vswr]

From 399's (sadly defunct) site:

Locate D23 (next to VR7). In the Realistic rigs a 220 ohm resistor is in the D23 location. Replace this resistor with a 1N914 or 1N4148 diode. (observe polarity). This change will make the Realistic 858 mod limiter the same as all of the other brands. Really opens up the audio. Replace C87 with a 10uF 16v electrolytic cap.

Gotcha! Will get at that asap! Thanks and 73s! Great help from all you guys!

 

[vswr]

From 399's (sadly defunct) site:

Locate D23 (next to VR7). In the Realistic rigs a 220 ohm resistor is in the D23 location. Replace this resistor with a 1N914 or 1N4148 diode. (observe polarity). This change will make the Realistic 858 mod limiter the same as all of the other brands. Really opens up the audio. Replace C87 with a 10uF 16v electrolytic cap.

Done! No kidding! Who needs a power mic when you have mod like this. I had to tone it right down its a screamer! Thanks forcthatbtip!

Sadly, I am still having constant issues with ct2, ct3, and AM. Turn one and it offsets the other. Then adjusting AM through it all out of alignment again. If I go by the sams adjustments, my center is at 2 oclock on lsb. Ive never had a radio so tough to align like this. I tried using a mini muffin fan to cool down the TO3 transistor but I can hear the fan through the speaker especially loud on AM. Might have to figure out a way to isolate it because somehow the motor rotation sound is feeding back into the DC and then working its way into the audio. Maybe using shielded wiring or using a voltage regulator like a 7812 or both. There has to be some method to keep it from drifting but I'm lost.

 

[loosecannon]

VSWR,

something you said in one of your posts prompted me to ask, what color is the heat sink compound you are using?

you said "top of the line CPU compound" and many times that type of compound is conductive.

if the compound you are using on that TO3 transistor is grey/silver, then i would say thats your issue with the heating.

you need to use the white silicon non-conductive grease.

just a guess but i thought i'd mention it.
LC

 

[vswr]

VSWR,

something you said in one of your posts prompted me to ask, what color is the heat sink compound you are using?

you said "top of the line CPU compound" and many times that type of compound is conductive.

if the compound you are using on that TO3 transistor is grey/silver, then i would say thats your issue with the heating.

you need to use the white silicon non-conductive grease.

just a guess but i thought i'd mention it.
LC

Good point! I havent done it yet but yeah it would be conductive. I'll stick with the white stuff. Thanks!

 

[loosecannon]

ok well then that's not the problem.

I apologize if this seems pedantic but have you done a continuity test from the body of that transistor to the metal chassis of the radio?
LC