>
>On Sun, 7 Dec 1997 11:26:57 EST JW KIMBALL <JWKIMBALL@aol.com> writes:
>>Well the old saying of keep the smoke inside or it will quit working
>>seems to
>>be true.
>>
>>My TL922 smelled so I turned it off. Upon opening I found:
>>L7 on V1 smoked
>>R22 on V1 smoked
>>C33 and C32 on V2 smoked
...
...snip...
>Sounds like a simple case of internal arcing in the tube. A 10-20 Ohm
>resistor in the HV lead would possibly have minimized the damage.
>The grid chokes are also way too large in current capacity. Replace with
>150-200 ma types which have both extra resistance to provide a bit of
>degeneration and will act better as current absorbers.
>
Chokes make flaky fuses. Ordinary carbon film resistors are easier to
blow than chokes, and they are cheaper. Fast-acting 0.25A 250v fuses
would probably work.
>In extreme cases when the tube arcs or shorts you will also take out the
>Zener D-2, and Bias diode D-1 and caps C-3 and C-26.
If a gassy tube arced between the anode and the grounded grid, how could
current flow in the cathode bias Zener?
- With zero volts bias between the grid and the cathode, the tubes draw
around 300mA of cathode current. I don't see how 300mA could blow the
cathode bias Zener, Carl.
>If the amp failed while on 10/12M best to check PC-1 and PC-2 R values
>also. Replace with metal oxide.
>
Good advice, Carl, except that I would not be as hasty to replace the
resistors. 10m heating produces changes in the external appearance of
the resistors. If there is no external sign of overheating, and the
resistance has increased substantially, it is unlikely that 10m or 12m RF
did the damage.
Rich...
R. L. Measures, 805-386-3734, AG6K
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