Common items you passed up that turned rare when you wanted them
dwight.elvey at amd.com
Tue Jan 31 16:48:09 CST 2006
No, even the tube may be revived some. You can
often run the heater at a higher voltage for some
time and check the emission periodically. Usually,
you can safely run the filament at 1.5 to 2 times
the rated voltage for 5 or 6 hours. It is usually
done with no cathode current while at the higher
voltage and then return to normal levels to check
for the current. It would help to have a tube
tester but I suspect that just measuring the voltage
drop across a resistor in the cathode circuit
someplace would tell if there was any improvement.
You graph the increase in current. At some time,
you don't get any improvement so you stop there.
No sense wasting the filament.
You could control the voltage with a variac
and a transformer.
Do make sure that the tube is the cause. Raised
voltage on the filament can shorten the life of
the filament and at times cause cathode to
If the image is well focused and not over sized,
the main rail voltages are OK.
>From: "Richard" <legalize at xmission.com>
>In article <200601311927.LAA29559 at ca2h0430.amd.com>,
> "Dwight Elvey" <dwight.elvey at amd.com> writes:
>> >[...] I do have one monitor. I haven't tried
>> >to power it up, but written on the case is the word "DIM", presumably
>> >identifying a failure in the monitor somewhere. I've never repaired
>> >monitors, so I'm not sure what a dim image is suppose to indicate.
>> >Failing HV drive circuitry?
>> HV would cause blooming of the image. Dim image is weak cathode
>> in the tube or problems in the circuits controlling the cathode
>> to gate voltage levels.
>So... if its the tube, there's nothing to do but replace the tube?
>Egads... I wonder how hard it would be to find a compatible
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