>
>
>-----Original Message-----
>From: measures <2@vc.net>
>To: AMPS <amps@contesting.com>
To: <amps@contesting.com>
>Date: 13 September 2000 02:36
>Subject: RE: [AMPS] Blown TL922A... What to do?
>
>
>>
>>>
>>> I like the idea of modeling the circuit. However,
>>>much of the circuit is not considered. People often don't realize that
>>>that there are additional inductances due to the current paths thru the
>>>chassis and often these impedances are in both the input and
>>>output circuits. I have seen many amplifiers that have very long paths
>>>from the anode (PLATE) thru the coupling capacitor, PI input capacitor, to
>>chassis and
>>>back to the grid and cathode circuit. Sometimes this path is a foot in
>>>length or more
>>>. This single loop amounts to nearly a uH of inductance with
>>>who knows what other impedances tied to it and signals sharing the path.
>>> My electronics instructor used to say often the problems with a circuit
>>>is the component you can't see. Especially with RF circuits.
>>>
>>Amen to that, Bill. Who would ever have guessed that there is a
>>Z-step-up L-network hidden inside the Tune-C in a 922?
>
>
>C'mon, Rich, make with some details. Where's the L, where's the C, what are
>their values, and do they predict the required voltage step up?
>
Good point, Steve. This is perplexing. The tune cap. connects to c.
27mm of #12 busswire, so that could be involved with the series
resonance. The trouble with schematic diagrams is that they are quite
accurate.
I have heard of many 6000v tune caps that arced over in TL-922s. The
peak potential at C-Tune should be no more than 2800v. Something weird
has got to be stepping up V.
>
cheers
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
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