Ok, now we have to find what happened...
As before - when things get hot, in the regulator - there are only several areas it feeds.
Mostly PLL, Display (LED Channel) Dimmer, MIC amp, AWI and the main Xtal (10.240) and IF (where pure quiet filtered DC is a must).- lastly the PIN diode section needing a quiescent current to help with RX noise.
This regulation is also sent to CB/PA switch - so when you switch to PA, TX switch and it's section turns off - If TR23 should cool down, then this is because it's output DISABLES TX but not the PLL - this PA mode may help isolate the draw heating up problem - if it gets (TR23 ) cooler, then the TX Switch area was at fault and needs investigation. (That has happened - hence the things to check are revered installed caps, they can stand some reverse voltage but hiss and leak vapors of sulfur smelling odors... along with drawing a lot of current in the process)
Very little else goes to regulation - all the other sections including Squelch - it's power is arrived to thru filtering and a diode
D21 - the Diode blocks the "backfeed" from cycling thru the regulator forcing it to drop current thru it trying to keep the radio working - it thinks it's a surge, the Zener would be cranked into conduction...so the part attempts to sink current thru itself - which will damage it..(D21 gives it Reverse Polarity protection too)
So knowing this may happen, they use R103 - 200 ohm 2W resistor as a bypass - it provides some cushion so that TR23 doesn't have to work so hard at regulation. It parallels TR23 - so it will sink current thru it - so if you're having issues, you may need to check R103 and ensure it's value is 200 ohms. This is a tricky section, for too much ohmic resistance - TR23 works harder, if you use too little - the current drawn thru TR23 will not be enough to keep voltages down to regulation levels - extra noise and erratic IF / RX operation.
- Some people I have done mods for, wanted Echo inside (amongst other) but needed an ~8+ Volt feed - which requires you to lower R103 to about 180 ohms, but keep the 2W rating - this keeps TR23 from blowing up - else if the Echo or other toy needs more current to operate, in comes the NTE-37 to it's rescue.
IF you feel the necessary needs, you can always sub in a NTE-37 - Hilarious but I've seen it done - will need your very idea of heat sink panel to dissipate heat from this...
Another aspect is the regulation circuit itself - Follow the current trail - Branches and all...
Capacitors...
- C119 - 100uF 16 volt, Regulator buffer/filter output
- C112 - 470uF 16 Volt, + 5V Regulator buffer/Filter output
- C114 - 100uF 16 Volt, + 5V Regulator INPUT Buffer/Filter
- C102 - 47uF 16 Volt, + 5 Volt INPUT Filter for PLL
- C11 - 10uF 16 Volt , PIN Diode Power / BIAS for RF GAIN
- C66 and C67 - MIC amp section past (R70) buffered thru a 330ohm resistor
So you have some work ahead of you.
This is why - when I saw the "red wire" looping back to ground - plus the harness work, I know that the meter lamps always need to be replaced, not everyone keeps the same wire coloring to help - but then too - I've had radios that used a meter lamp installed at the switch, but used so much heat they put a short across the switch. S205 t's a Dual Pole unit. One side feeds the Dimmer BASE circuit but gets power from the Regulator. The other side is 12V straight from the battery The lamp uses 12V thru a dropping resistor so you need only an 8Volt type for best illuviation results. But even with the best works done to it, it's still possible to "overheat" the switch and the contacts remelt together - this happens on old radio switches, they used Butyl-based plastics so they can show heat deformation (let alone stink). You had to move/slide the switch to the position of the contact underneath the tab so the heat would not deform it so quickly.
Sorry to see you lost the radio but TR23 heating up means more work needs to be done, so you may have lost the Regulator but you also may have lost the power filter section too - again - Bad - Old caps or reverse installed ones, can do the same thing. IF someone tried to mod it - they you have to find those sections and undo that damage as well.
I've given you a list of Caps in the feeder line from the Regulator - most are buffered thru a resistor - but if TR22 is bad, you can send full battery voltage back into the 8~9 volt regulator circuit (Short from Collector to Base) forcing TR23 to sink more current...
Ok, you have all my Cliff notes on this...