[AMPS] Blow TL922

[measures]

>
>
>HERE IS THE STATUS SO FAR !!!
>
>Hi there.
>
>Thanks for all these useful replys. I never used such a
>great source like this one.
>
>I located the zenner diode as defective but it takes
>about 1-2 weeks to get a replacement. 

The zener diode can be replaced with a series of c. 7, 1A forward-biased 
diodes. Such an arrangement is much more rugged than a zener.  

> The L2
>between grid and ground is also defective. 

The 470uH grid choke can be replaced with a 1/4 to 1/2 W carbon film 
resistor to act as a grid fuse.  .  .  R can be 20 - 30 ohms.  Add c. 
1000pF to the existing grid bypass to protect the fusing resistor from 
15m / 10m RF.  The fusing resistor helps to protect the tube from 
filament to grid shorting during the intermittent 120MHz osc.  //  It is 
good precaution to high-pot- test a 3-500Z/8008 that toasted a choke.  If 
the withstanding V between fil. and grid is not at least 6kV, a short my 
result when the tube is hot.  A shorted tube will destroy the filament 
transformer in a factory-stock 922 (or SB-220) unless the amplifier is 
promptly switched off.  To avoid the problem, Disconnect the pos. 110v  
source from the bias contacts on the relay.  Connect the existing 100k R 
across the Common and NO contacts.     

> It's a
>470 uH one wich is not easy to find. That will take
>also about twoo weeks.
>
>I keep you updated ....
>
good luck,  Helmut 
>____________________________________________
><A>bort, <R>etry or <I>nfluence with larger hammer !
>
>-----Ursprüngliche Nachricht-----
>Von: Helmut (DF7ZS) <df7zs@gmx.net>
>An: AMPS@contesting.com <AMPS@contesting.com>
>Datum: Donnerstag, 24. Februar 2000 13:37
>Betreff: [AMPS] Blow TL922
>
>
>>
>>Hi there.
>>
>>I have a TL922 by Kenwood and the folowing happend to it:
>>
>>On Standby-Mode (after some minutes operation) I heard
>>a loud "bang" . As I looked on the panel the IP-Meter was
>>showing 500mA. Remember the Amp is set to STANDBY
>>not to operate nor the PTT is hit.
>>
>>My guess was maybe a missreading so I pushed the PTT
>>and sended out a short burst via mike. The Power meter
>>showed that the AMP is delivering about 1000 watts as
>>normal. Back to standby - the IP reading is still 500mA.
>>
>>I turned the thing off.
>>
>>Any Ideas what happend ?
>>Anyone had a simular problem in the past ?
>>I am also seeking for a Service Manual to
>>download or faxpoll.
>>
>>Thanks for any help !!!
>>
>>73sss
>>
>>            Helmut (DF7ZS)
>>____________________________________________
>><A>bort, <R>etry or <I>nfluence with larger hammer !
>>
>>
>>
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>
>
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>

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