[AMPS] Blown TL922A... What to do?

[measures]

>
>> Has anyone been able to measure the frequency of oscillation in, for
>> example, TL922? What dip frequencies are found with a GDO in a 922? In
>> other amps?
>
>
>I'm missing something in the above Steve.
>
>Tell me how a GDO can be used to measure the mode of 
>resonance? How do you know the impedance is high, instead of 
>low? How do you know what you are measuring in a complex 
>system, since it has no directional ports?
>
>I can dip my amplifier tank on 1.8 MHz. Does that mean it 
>oscillates there also?
>
>These are serious questions, don't take them as flip remarks. I'd 
>like to know those answers.
> 
>> >Of course you nee a real amp to measure. What amplifier do you
>> >have available? If you have one that I have, we can go through the
>> >measurements and compare results on here.
>> 
>> 
>> I don't. I've never mastered a straight key, so I've not been able to pass
>> the code tests to get on hf over here. A degree and 25 years designing rf
>> for a living doesn't count. I'm hoping to sidestep the system by taking
>> Extra class exams next month.
>
>OK, so you can't measure a PA...and haven't measured one. 
>Without doing that, on a device that measures impedance of 
>coupling between ports, how do you know all this stability 
>handwaving is true?
> 
>
>> For sure, if you have a low impedance at a given point and frequency, it
>> is difficult to generate high voltage there, and if you mistune the output
>> network you can get a high impedance and lots of volts at the tune C.
>> That's simple fact.
>
>You can get MANY times the normal AC voltage.
>
A test by the owner of a SB-220 indicated that the max. mistune potential 
for the tank was 3700v.  My own tests semi-confirm this.  

>As a matter of fact, underloaded tanks are commonly used in HV 
>supplies. TV sets use a "flyback" transformer that steps up voltage 
>far beyond the actual turns ratio, because it is an "underloaded 
>tank". 
>
>Your car uses a similar principle to generate the ignition pulse.
>
zzzzzz

>Remove the capacitor from an ignition coil, or the capacitance 
>resonating a flyback transformer, and the voltage will drop like a 
>rock to the normal voltage expected using the turns (impedance) 
>ratio. The same thing happens in a tank, and the TUBE is 
>subjected to those peak voltages just like the bandswitch.
>
>I can make virtually any HF amplifier arc and damage something by 
>mistuning or having the correct load fault/exciter transient.
>
If an antenna tuner cap. or a lightning-arrestor gap arcs, it is possible 
to arc the tank in an amplifier.  

>I can't make many of them arc by removing parasitic suppression, 
>and I've never been able to make a bandswitch arc that way unless 
>the PA oscillated at the fundamental frequency, or near it. 
>
bananas 
 
>> There's a few types of amp that crop up regularly here with problems, such
>> as TL922. Anyone near Newbury got one I can poke around inside?
>> 
>> Steve
>
>Try this test. Excite the anode with a VHF signal source, and move 
>downstream through the anode and tank system measuring 
>voltages.
>
>I'll send you $100 if you find a commercial HF amplifier that steps 
>the anode voltage UP as you move through the tank.
>
>I'm sure we will all agree that if, when the anode is excited by a 
>signal source at the frequency where the alleged "parasitic" 
>occurs, in order to cause an arc downstream, the voltage would 
>have to be stepped UP.

The VHF stepup L-network that arcs the bandswitch is hiding inside the 
Tune-C.  Congrats on making this important discovery, Mr. Rauch. 
>
>It would take about 500 dollars to buy brand new equipment that 
>would measure this effect, most people already have the equipment 
>sitting in there room.
>
€  ?

>Why, when such a measurement is so easy, haven't more people 
>made it?
>
500 bucks would pay for 21 trips to the best pizza joint in Camarillo, 
California. 

>That one simple measurement conclusively proves (I've made it) the 
>claims tank components arc from VHF parasitics on frequencies 
>far removed from the tank resonance is wrong.
>
€  Bad news, Tom.  You can not disappear the Tune-C resonance.  The genie 
is out of the bottle.  You win.  The self-recognized "expert" looses.  
>
later

-  Rich..., 805.386.3734, www.vcnet.com/measures.  
end


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