The Defpom Forum, for RadioMods, S&M Software and Music by The Defpom

This one has been boiling my brain for sometime since I havent been able to get on for a while. Well I am back and I finally get to dish this one out.

I do alot of work on radios, but have never put my hands in an amp literally. I got a tornado 100 today and the problem with it described to me is that it keeps popping the finals. I have not been able to test it yet as putting new finals in it is a bad idea knowing it will kill them.

I know a few things about how to fix the relay and sensing diodes for rf and the preamps, but when it comes to output power, havent stepped foot there yet.

Any ideas or suggestions on why the finals keep popping is welcomed and also do the numbers face the input or output transformer? Man, I been losing it lately not being on the net....

Umm, turning them around the wrong way will definitely pop them, and fast. If the amplifier has a bias circuit, it could have been damaged. If so, it could feed way too much DC bias current into the RF power transistors' base leads. THAT would pop them too, but usually not quite so fast. If you remove the RF power transistors, hook up the power, and then activate the relay, you should not see more than 0.6 Volts DC on the foil pad for each base lead. If you do, there's a problem with the operating bias. On the other hand, many CB linears have NO fixed bias circuit, and you'll measure zero Volts this way.

One lead will have a corner lopped off the end. That terminal is the collector, and it connects to the larger set of transformers on the amplifier's output side. The lead opposite that one is the base, and goes to the shorter set of ferrite transformers, the input side. The remaining two leads coming out each side are both connected to the emitter, and go to ground.

I found many years ago that not all manufacturers print the type numbers to be upright with the base lead towards you. Haven't seen any new ones with "upside-down" lettering in many years, but it got me out of the habit of using the type markings to orient them.

73

The amp could be oscillating at Audio or a lower RF frequency.
that could be an easy death 4 rf pills as the power of the oscillations could be easily higher than the ratings of the pills and that combined with bad matching of the circuit impedances and or antenna impedance / reactance at the frequency of oscillation would definitely spell death 4 the pills.
I also concurr with nomaradio about his suggestion as this is a definite possibility. Especially if there is no thermal limiting in the bias circuit.
All the best, Dazz In Auz.