Yes, As I said in the PM, that resistor is on the output combiner were the 2, 2 transistor sections are combined into one for the output.
If it burns, it tells you that you have an imbalance across the combiner.
One or the other of the 2 sections is not putting out the same amount of power as the other.
The Transistors are all of the same date code, and all 4 are red dot
Motorola uses two methods to designate d.c. current gain of RF Power Transistors, color dot or letter code.
You can find the table here
All 4 should be very close in gain and output with each other.
Very carefully go over your work and make sure that everything was put back the same as it was before you swapped the transistors.
If anything was not correct, it could have caused the 2 stages to be un-balanced ( one side making more/less power than the other)
Also check the Bias Mods you were doing to make sure it is all correct.
Did you do any testing of the Bias voltage after doing the modification?
Also, ( as I had already said in PM`s) the 455/453 have higher gain than the 1446.
With the 1446`s RM says that on AM not to use the #6 setting with input of over 12 watts, as the 455/453 has higher gain, it will take even less drive .
I would also Float the Tabs on the transistors and check them again, to be sure they did not get damaged.
Um, did you get time to take a picture of the board in the Amp?
73
Jeff
