The First test

This is a very initial test as soon as I replaced the choke.
To revive the old tube not used for a while, I guess that I will cook it without the HV applied. Then I will make the ande red to activate getter.


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Date: Nov. 12, 2006
Test gear: Bird 4413, Dummy 636N, Exciter= IC706Mk2G
Vac = 215 V (down to 210 V when key down) HV = CW (~2100 V)


FREQ (kHz) Po (W) HV (V) Ip (mA) Ig (mA) BAND
1820 800 1700 660 260 160
3525 900 1650 710 290 80
7050 950 1650 680 290 40
10110* 680 1700 520 190 20
14100 900 1700 640 260 20
18100 800 1600 760 270 15
21100 800 1650 680 250 15
24900 720 1700 650 220 10
28500 820 1700 660 260 10

* High input SWR

TL-922 plate choke rebuild

The Plate choke of TL-922A



Why this plate choke arced? My guess is that the voltage difference between the coil surface and the tip of the output capacitor exceeds the breakdown strength of the air (between the surface and the tip) at the moment. I will later add a silicon insulator at the tip of the output cap.

The coil diameter is about 0.33~0.35 mm.

I bought some enameled wire from the local wire shop on Saturday morning. Then I rebuild the choke coil as shown above. I tried to make it as similar as possible with a slightly different size of enamel coated wire. No time to measure actual coil inductance. (yeah, the test gear was far far away at that time)

I put it the amplifier and, it worked for all 9 bands!!

TL-922A fan specification

Rotron fan: AC 100 V 7.5W, 1.25 m^3/min (~44 cfm), 1300 rpm at 60 Hz, ~45 dBA

Those 3-500Z glass tubes require airflow of 13 cfm at 0.082 inches-H2O for anode dissipation of 500 W.

* Maybe I change it with a 88 cfm fan and some sort of heat-controlled fan-speed? or something smarter??

TL-922A Improvement

The broken TL-922A arrived via CJ shipping service on Oct. 25, 2006. It is heavy (~31 kg, the amp alone)