>At 01:22 AM 11/19/97 -0800, you wrote:
>>>is a 3cpx800a7 the same tube as the 3cx800a7 (difference being the "p").
>>>and can 3cpx800a7 be a replacement for the 3cx800a7 in my titan amp?
>>>thanks....Steve
>>>
>>The 'p' usually means rated for pulse duty. It outta work ok in linear
>>service. Are you replacing kaput tubes in your Titan 425?
>>Rich---
>>
>>R. L. Measures, 805-386-3734, AG6K
>>
>>
>
>No Rich. I just got these tubes for a spare set should I ever need them.
>Hopefully, I won't. Any idea on how long a set of these tubes should last
>under reasonable conditions ? ...
>
With 13.0 v on the heaters, probably about 20k hours, Steve. However in
the Titan 425 I worked on, both tubes were on the verge of failure after
25 operating hours.
- The symptom was an arcing problem somewhere in the hv circuitry. The
trouble was traced to loose gold melt-balls causing occasional
anode-to-grid arcs in the tubes. However, I was able to move the gold
melt-balls into the bases by tapping on the anode coolers, whilst
measuring the leakage current with a high-potential tester. When I
started out, the leakage current in both tubes was over 50uA. After
tapping, the leakage current decreased by a factor of around ten. The
final fix was to install lower VHF-Rp parasitic-oscillation suppressors
and to tape a "DO NOT INVERT" warning label on the top of the cabinet.
Rich---
R. L. Measures, 805-386-3734, AG6K
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