On Mon, 18 Feb 2008 22:10:47 -0500, DC wrote:
>How good is the final tube in a Titan 425 thats been un-used for
>ten years?
I agree with Bob that the most likely problem purely from sitting
is the lytics in the power supply. I would turn it on as Bob
suggested, letting the caps reform if they're going to. Chances
are at least some will be bad. But they may not blow -- they may
simply open, and that will show up as reduced plate voltage UNDER
LOAD, but not without a load. And you'll get reports of
hum/buzz/nasty CW note.
If that happens, kill the power and let the HV discharge for a
long time. Yes, there's safety protection, but when that safety
protection discharges the HV it can start blowing out transistors
and even melting a trace on the PS rectifier board!
To check the caps, use a traditional VOM like a Simpson 260 on its
medium R scale. Check the R in one direction, leaving the probes
in place long enough for the VOM to charge the caps, then reverse
the probes. A GOOD cap will show strong charge and discharge
current (low resistance) in both directions. A BAD cap will show
much less. Measure them all and you'll get a fell for what normal
is. Replace only those that check bad, then fire it up and repeat
the process. Chances are if one is bad another will be.
BTW -- there is a detailed pdf of the schematic of the Titan 425
on my website. http://audiosystemsgroup.com/publish It shows
everything but the RF (which is by far the simplest part).
73,
Jim K9YC
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