On Sun, 11 Oct 98 15:40:13 -0800 Rich Measures <measures@vc.net> writes:
>>
>>
>>On Sun, 11 Oct 1998 01:29:16 -0700 (PDT) igor rosky
><irosky@yahoo.com>
>>writes:
>>>
>>> I have just lost a 3-500z in TL922, it has also caused a lot of arc
>>>damage to the load capacitor, which has very fine plate spacing,
>does
>>>anybody know if this is still available from Kenwood, or is there a
>>>suitable substitute that will fit in its place.
>>>
>>>Igor
>>>
>>
>>Arc damage more likely caused the 3-500Z to fail.
>
>How would an arc at the Load-C cause tube failure? An arc looks like
>a
>low Z load -- and that would produce little or no grid current
>compared
>to a 50 ohm load.
If the antenna relay or antenna presented an intermittent open circuit
the resultant grid current may have damaged the tube over time. Repeated
TL-922 hot switching can and does cause relay contact spacing to change
over time futher exacerbating the problem.
Arcing only occurs after the capacitor voltage breakdown is exceeded.
On another note, the SB-220 Load cap IS NOT a replacement for the TL-922.
Completely different values and dimensions.
The SB220 is 800pf total and the 922 is 1920pf in 2 switch selected
sections.
Kenwood part # is CO2-0008-05
73 Carl KM1H
>
>> That Load capacitor
>>does not like high VSWR or hot switching from that archaic TX-RX
>relay.
>
>amen
>>
>>Kenwood still carries TL-922 parts, check their web page or call
>>310-639-5300 for the Service Dept.
>>While you are at it make sure there is no damage to the grid and bias
>>circuit components.
>>
>>Cant blame this one on parasitics I bet!
>>
>If the damage is only to the Load-C, I agree. Only a high-pot will
>tell
>whether the fil. helixes are bent or not.
>
>
>Rich. Measures. Web site: www.vcnet.com/measures
>
>
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