Hrm, do those booster/isolation units come with instructions? How does the
boost work? I will avoid it if possible.
Do these boosters work with the high frequency of the filament winding from
the flyback? I thought they were only for units that used 60 Hz to power
the filament.
Couldn't I just use the current winding on the flyback, and remove the ground
reference? My board does not have a Wintron flyback, but the new replacement
flyback that became avalable in the last few years. I think if I just
unsolder the resistor that is conected to the wire on the core, and the
other end of the wire, and connect them directly to the heater connector,
that should be isolated. I'm just wondering if that may impact other
windings in the core as the filament now have a new reference about 180 volts
(which is gets from the short in the CRT).
___
Ken
Rodger Boots wrote:
> If you use the isolation/booster transformer, avoid boost unless you
> have no other choice.
>
> On Sep 27, 2013 2:06 PM, "Rodger Boots" <rlboots2@gmail.com
> <mailto:rlboots2@gmail.com>> wrote:
>
> Isolation used to be done with an isolation transformer. These are
> getting hard to find.
>
> Do NOT recommend tapping on the neck or the "blow the short out"
> techniques---not for heater-cathode shorts.
>
> See EBay item 150546845743.
>
> On Sep 27, 2013 1:43 PM, "Ken Sumrall" <k_lists@scrapheap.net
> <mailto:k_lists@scrapheap.net>> wrote:
>
> And Rodger guessed correctly. Sad face for me. :-(
>
> After probing around with a scope, and checking signals, it
> became clear
> something was going on in the tube. So we swapped the blue and
> green
> drive wires in the connector, and powered it back up. If the
> issue was
> with the electronics driving the tube, we expected the overall
> gree hue
> would become blue. And if the problem was in the tube, it would
> stay
> green. And it stayed green.
>
> After some research, we found this:
>
> http://www.repairfaq.org/REPAIR/F_monfaqa.html#MONFAQA_002
> <http://www.repairfaq.org/REPAIR/F_monfaqa.html#MONFAQA_002>
>
> And it looks like our three choices are:
> 1. Tap the neck (gently) with the crt face down and try to
> dislodge the short.
>
> 2. Try blowing the short out (with a current pulse), but this
> risks blowing out the heater filament too. I have a Sencore
> CR-70 which I recently acquired, but I've not yet powered it on.
> And the manual says it doesn't clear heater-cathode shorts
> because it can blow out the filament too.
>
> 3. Remove the ground reference from the filament and float it.
>
> The last option sounds intriguing. Does anyone think this is a
> bad idea?
> Do I need to worry about improving insulation on the heater
> winding or wires to the CRT? IIRC, the cathodes are only about
> 180 volts, so I think the insulation on the wires will be
> sufficient. Will the floated voltage on the wires affect other
> coils in the flyback? If so, we could create a separate power
> supply for the heater.
>
> Comments? Suggestions?
>
> ___
> Ken
>
>
> Rodger Boots wrote:
>
> Heater-cathode short in CRT green gun? Don't suppose you
> have a CRT tester?
>
> On Sep 11, 2013 6:10 PM, "Ken Sumrall"
> <k_lists@scrapheap.net <mailto:k_lists@scrapheap.net>
> <mailto:k_lists@scrapheap.net
> <mailto:k_lists@scrapheap.net>>> wrote:
>
> The monitor on our Star Wars sit down machine at work is
> having
> issues. It started with an intermittent issue where the
> screen
> would suddenly turn green, and it was very bright and
> all the
> retrace lines were showing, and all the lines were out
> of focus.
> Smacking the cabinet would sometimes bring back a good
> picture.
> Then we also lost vertical deflection, so we opened it
> up to take a
> look.
>
> The deflection issue was easy to fix. We replaced a few
> transistors, and a fuse, and it was working again. The
> other issue
> we're still struggling with, in fact it's much worse,
> and is mostly
> in the bad state, with occasional flickers of it working
> correctly.
>
> We initially thought it was a bad connection in the CRT
> socket, as
> it seemed to change as I was poking the socket with a
> wooden stick.
> So I replaced the CRT socket harness with a spare one I
> had. That
> didn't work. So poked some more, and started to think
> there was a
> loose connection in the focus block. But then poking
> further didn't
> do anything.
>
> So, we started to suspect that something is just
> randomly working
> for short moments, and whatever I was poking when that
> happened made
> me think that was the issue.
>
> We are now wondering if maybe the green drive transistor
> is shorted
> on? That would explain everything looking green, and
> the retrace
> lines, and the brightness. Would that also explain the
> poor focus?
>
> Any other suggestions?
>
> Thanks!
>
> ___
> Ken
>
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Received on Fri Sep 27 15:23:19 2013
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