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

[measures]

>
>> >You must be using a new definition of resonance. Can you tell me 
>> >what you mean?
>> >
>> zzzzz
>
>Sounds like you have outgassed. You need to take more nichrome.
> 
>> >This is a series-resonance, not L-network, and it is shunting the 
>> >path the tube must drive on VHF.
>> >
>> L-networks transform Z.  They shunt not.  
>
>Nice diversion, but it is not an L network at work. It is a series 
>resonance.

€  The Tune-C series-resonance frequency is Near the oscillation 
frequency - but not on it.  This is what transforms the Tune-C into a 
Z-stepup L network.  
> 
>> >If the tank could freely pass harmonics, or step up the voltage at 
>> >VHF to high levels, the amplifier would be a TVI nightmare. 
>> > 
>> If the tank were a high-pass Pi, VHF parasitic oscillation would be 
>> unlikely.  
>
>So you are saying an amplifying device driving a high load 
>impedance, all other things equal, is more stable than an 
>amplifying device driving a low impedance?
>
€  No.  

>You can do better than that Rich, you are arguing against your own 
>sales pitch!
>
>If the network looked like a high impedance as you "propose" 
>above, 

€  I did not propose this.  What makes you think that L-networks have 
high input impedance?

>instead of a short circuit, the amount of ESR used to 
>dampen the anode would have to be greatly increased. Any series 
>resistance would be a smaller part of the overall system 
>impedance, and for a given resistance Q would be reduced less.
>
>The tank is typically a virtual short for VHF and UHF energy, 
>because it has a capacitor shunting the input. 

€  The Tune-C is being operated *Near* a series resonance. 

>All your claims 
>about VHF parasitics damaging components are just "arm-waving" 
>to sell kits and slam manufacturers. 
>
€  Manufacturers discredit themselves.  For example, Bridgestone / 
Firestone  apparently knew about the tread separation problem in 1992, 
yet they did not fix it.  About the same time, I was driving my Dodge 
maxivan on the freeway when a sudden tread separation occurred in a 
Bridgestone tire.  So how did this happen?.  In a word, the answer could 
be *ringeshow* (pronounced rin-gay-show).  Ringeshow is a Japanese word 
which means that needed changes can Only come from the Number One (dai 
ichi) manager.  Any other person in management who suggests that a change 
is needed will almost certainly be booted out of the company because he 
violated ringeshow by dissing the #1 dude.  
Apparently, Ford also knew about the tread separation problem eight or so 
years ago, and they did nothing.   .  .   Ringeshow.  

At this moment, two 8877s which suddenly failed in an AL-1500 are being 
shipped to me.  My guess is that gold-sputtering is present in both.  
Eimac said that gold-sputtering results from oscillation.  If the tests 
proves me wrong, all of you will hear it here.  

>> >The impedance of the capacitor is highest at dc, and is reduced as 
>> >frequency is increased. That's why the tank is a low-pass network.
>> >
>> >If the parasitic is NEAR the fundamental frequency, or lower than 
>> >the fundamental frequency, it could indeed arc the tank 
>> >components over...maybe. 
>> >
>> At the HF/MF fundamental freq. there is not enough feedback C to sustain
>> oscillation.  
>
>That isn't always true, especially with tubes like 811A's and 572's 
>or tubes that don't have the grids correctly grounded.
>
€  Does anyone who owns a dipmeter know where a grounded 811A grid 
resonates?.  
 
>> >Nice try. Now we have single frequency parasitics exactly on 120 
>> >MHz, where the tuning capacitor has about ten ohms of reactance, 
>> >driving the tank capacitor with thousands of volts.
>> >
>> Mr. Rauch conveniently disappears the series-resonance in the Tune C to
>> support his agenda.
>
>Mr. Measures fails to understand series resonances have lowest  
>impedance, and less impedance than either "component" alone, to 
>support his nichrome sales. 
>
€  I know abundantly well that series-resonance has low Z.  PLEASE READ 
CAREFULLY
THE TUNE-C IS BEING DRIVEN WITH ENERGY THAT IS *NEAR* THE 
SERIES-RESONANCE, Tom. 
  
>> >What happen to your claim about grid resonance at 80 MHz, did it 
>> >move in this application to fit your needs?
>> 
>> no.  The tubes can oscillate above grid resonance. 
>
>Interesting. First they do, then they don't. Nice arm waving.
>
€  They can still oscillate.  We can't do anything about grid resonance.  
Lower Q VHF suppressors are seemingly needed.  
>
later, Tom.

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


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