General Lee question for the CB Repair Experts

Are you using a cheap meter?
Could be an unstable meter.

 

TR51 has been overheating and is likely leaky and thermally unstable. Often caused by many possible factors. Diode mods in the area on the bottom near the feet of TR51, or one in series with R238, and so on. Or R238 being changed to a value above 5,600 ohms. In short it may be going bad from excessive peak currents. A final or finals (if newer HP model) could be drawing excessive current. Antenna problems could have caused this to begin with. Or bias could be cranked too high by techs who do not really know the chassis. Poor antenna ground could be making the radio unstable. In any case TR51 is likely overheating and if leaky replacement is your fix, setting bias and other parameters properly, removing mods, and so on. You can replace the ceramic insulator with a large mica, clean everything and apply new heat sink grease. This gives better heat transfer out of it. Do not do this to the finals it will create too much capacitance from collectors to the wall. Best choice is a TIP36C. If metal tab you need to get the proper insulating hardware for the mounting screw, if plastic body then not needed. You will find they make both types. The extra capacitance will not bother it as TR51 only sees audio frequencies and the factory ceramic insulator really blocks heat transfer compared to mica. If TR51 is the problem you will notice talkback level is not stable, going from quiet to loud to actual squeal at times as it's temperature rises too high, especially if it is now leaky. In any case you need to find out why it went bad so the repair will last. As I stated mods especially combined with excessive bias or leaky finals are often the cause. Best before you replace things you talk on it checking first to see if one final is running hotter than the other. Usually you will notice lower than average power. If the finals are OK set the bias properly then move on to investigating TR51, of course inspecting for a diode swing mod in series with R238, or positive peak expansion (PPE) or negative peak compression (NPC) mods. Or one day you will be back where you are now.

 

RadioActive has been known to volt
the finals. I am surprised it has lasted
this long.

 

Wow your getting twice as many watts
out of that box as you should be.
Good job.

 

Keep in mind SWR could still have been an issue, except in your case it was what the radio saw looking into a very poorly designed input circuit in the amplifier. The other comment about volting finals - yes crap mod but remember this removes most current flow from TR51. Meaning while the finals could still be the problem due to being cooked, this scenario is unlikely from consideration of the TR51 issue. It would have then seen only the 2166 driver current, unlikely to ever be able to overheat TR51. By the way my TR51 comments are more from experience over many years and not so much theory, except as it applies to diagnosing your radio sight unseen. So Radioactive is still doing those mods? Amazing, when will people ever learn.

 

Radioactive would never get my business.....I have read on so many forums the bad results from them.