>Hi All -
>
>I am looking for some advice on the repair of a TL922A.
>
>I had been checking out a TL922 that I had not used in a year, when it
>developed a problem. When tuning up on 15, the power suddenly dropped for a
>second and then one of the fuses blew. After replacing the fuse, the amp
>came back on but the output would not go much over 400W. It seemed like
>only one tube was actually being used. As it turns out, when I looked at
>the tubes during transmit, only one of them was turning red.
>
? The 922 has a tendency to take off intermittently c. 120MHz. When this
happens, there is a surge in grid current, This problem and the fix is
discussed in articles on my Web site. Also see article on SB-220.
- To save fuses when troubleshooting an amplifier, clip-lead a 300W, 120v lamp
across each fuse holder and remove the fuses.
>When I opened the amp, I did not see any obvious damage and I planned on
>replacing the tube with a spare that I had. Before doing so, I decided to
>look under the tube. What I found is that one of the coils between the grid
>and ground looked melted (but not burned) and was no longer a DC short.
>
>My question is what may have caused this problem. Did the coil merely fail
>(I vaguely recall replacing one of these before) or could something else
>have failed, such as the tube, that caused the coil the fail.
>
>The complication here is that the amp is in Barbados so I cannot do any
>further diagnosis and I must bring down any spare parts that I might need.
>Therefore any insight prior to my next trip would be appreciated.
>
>As a general comment, I was surprised to see this method of grounding the
>grid. Is there a better way to do this that I should consider.
>
>73, Tom W2SC 8P1A
>
>
>_______________________________________________
>Amps mailing list
>Amps@contesting.com
>http://lists.contesting.com/mailman/listinfo/amps
>
Rich, AG6K, 805-386-3734, www.vcnet.com/measures
|