Shouldn't be a problem in removing the ground reference.
Modern isolation/boosters are probably all made to be driven from a flyback.
At a total of $11 their isn't much risk involved in trying it. And with the
number of wires on this beast I wonder if they aren't creating their own
virtual ground reference/protection against high voltage spikes that could
damage the other guns.
On Sep 27, 2013 2:23 PM, "Ken Sumrall" <k_lists@scrapheap.net> wrote:
> 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>
>> <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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