[South Florida DX Association] TL -922 amp users

Norman Alexander npalex at bellsouth.net
Sun Nov 28 13:12:23 EST 2010


Members-

I ran across this "warning" regarding the keying voltage/circuit of the TL-922 
amplifier and thought it might be of interest for anyone using or contemplating 
acquiring that model amp.  



Norm W4QN

=======================================================================

> After connect an amplifier TL-922 to PAPTT ( jumper in RE
> position), my MKII is crashed and lost the firmware, USB is
> detected but no load new software.

TL-922 is a *very bad* PTT design.  Not only does it use a
HIGH NEGATIVE voltage for the relays, there is *no* "spike"
diode, no capacitor to damp the spike and no resistance in
the PTT line to limit the current.  I strongly recommend
that any TL-922 owner install a "soft key" upgrade like the
SK-220 from Harbach Electronics:
<http://www.harbachelectronics.com/_mgxftp/pdffiles/SS100SK220TL922.PDF>

Without a soft start modification or the use of an EXTERNAL keying
relay, the TL-922 generates a large negative spike on the PA PTT
ground (return) and the chassis of MK II.  This spike can result
in REVERSE voltage on the solid state devices which will result
in failure that is not covered by warranty.

73,

   ... Joe Subich, W4TV
       microHAM America
      http://www.microHAM-USA.com
      http://groups.yahoo.com/group/microHAM


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