Re: We are KILLING our HV diodes...?

Here is more of the discussion:

----------------------><-------------------------
The problem in this is that when grounding the tube you also ground the
cascade.
The very high charge, especially when just turned off, is present on the
anode but ALSO on ALL stages of the cascade.
As you probably know the cascade is a chain of hightension diodes built in
a solid state housing.
The discharge can cause the underlaying diodes in the cascade to discharge
THEIR charge through the "upper" diodes, thus blowing them.
IE, the charge can eventually blow from linetransformer THROUGH the entire
cascade.
Sometimes these units are built together in a single housing, making the
exchange even more expensive.

Just one tiny little resistor, costing almost zilch, can prevent this.

Check this out, some TV's have a build in discharge unit almost exactly the
same construction as you described, only with a built in resistor.
Other manufacturers put a warning on the picture tube to discharge only
with a resistor.
Now why would they do that ?

I'm also aware of the fact that this resistor is not always used by
"qualified" service personnel.........
So far the statement qualified.

The cascade won't always blow, but it sure can and sooner or later you will
find that you just did ran out of luck (and a lot of money)

Hans
---------------------------------><--------------------------------------

Now, I think he is REALLY on to something here, and feel it is our best
interest to consider following his recommendations, especially as one of
our most serious problems relate to both Flyback (Linetransformer or
HighTension overseas) and or the HV diode (like on the B&W Vector games).
We settled on a 3 to 5 watt 1M resistor as having the best chance of not
internally shorting, yet doing the job with little risk to the diodes.

You are on your own now...I will be sending a synopsis of this to the
Monitor FAQ, as well as the news groups later today...and updating my web
page on monitor removal!

John :-#)#
At 11:49 AM 4/22/2000 , Matt J. McCullar wrote:
>I'm not sure I understand this. If you've got the power disconnected,
>and you discharge the CRT by grounding the anode, how can that damage
>the diode in the HV cable?
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Received on Sat Apr 22 16:03:15 2000