[Amps] TL922 Problem.

[Rich]

>Hi everybody:
>
>After both CQWWīs, SSB and CW; my old 922 (16 years) itīs so tired. I have
>some problems with the T2 (see photos); itīs ok the Ip and Hv but the relay
>donīt works and itīs smells bad (like a toaster). I need to know the
>reference of this transformer to replace it, but havenīt the reference. Can
>anybody helps me?.

T2 is usually destroyed by a tube that shorts from the grid to the 
filament/cathode.  When a short occurs, the +110VDC relay power supply 
shorts to ground and the unfused transformer becomes toast during RX 
unless the 922 is quickly switched OFF.  
The grid-filament short is apparently caused by a surge in grid current 
when the TL-922 intermittently oscillates at c. 120MHz. (photo of shorted 
3-500Z on p.15 of Sept., 1990 *QST*, "Parasitics Revisited"). //  To fix 
such an amplifier, the toasted transformer and the shorted tube must be 
replaced.  (the shorted tube is usually the one with the damaged grid 
RF-choke).  To prevent a repeat of the same problem, lower-Q VHF 
parasitic suppressors can be installed.  All of these problems also apply 
to the SB-220 - which Kenwood-san seemingly copied.  An article on 
Circuit Improvements for the Heath SB-220 appears on my Web site.
>
>Thankīs in advance, and Iīm waiting for Santa, with a new amplifier.
>
Currently built amplifiers are not without some of the same problems, so 
better ask Santa to bring you a soldering-iron.

have fun, Pedro 

>73 DX de Pedro, EA 4 KD
\

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