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Hints, Tips and Solutions (Do NOT post requests for help here) If you have any useful general hints and tips for vintage technology repair and restoration, please share them here. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

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Old 24th Aug 2017, 9:27 pm   #1
Karen O
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Default The wonders of slug tape

I recently rebuilt a CRT NBTV monitor into a more compact enclosure.

Everything went fine, except I now had patterning on the raster!

I knew straight away what the problem was: the field from the little LOPT. It was causing tiny deflections of the spot, especially at the side of the screen closest to the LOPT.

I knew from past experience that the patterning is nothing to do with the CRT voltages. It is a kind of velocity modulation as a result of the tiny deflections.

Anyway, the solution was a flux band around the LOPT and copper slug tape was just the job.

For the non horticultural, slug tape is adhesive copper tape that you stick around your pots to deter slugs (it apparently gives them an electrical tingle that they find objectionable).
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Old 24th Aug 2017, 11:29 pm   #2
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Default Re: The wonders of slug tape

I think we used to call a similar thing "spot wobble," this was deliberately introduced from the frame output circuitry and could be switched on and off.
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Old 25th Aug 2017, 1:12 am   #3
Karen O
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Default Re: The wonders of slug tape

Hi Alf,

My monitor actually includes spot wobble. There's an additional coil just behind the centring magnets.

I'd happily exploit the field of the LOPT if only it produced an even band of light. Instead it causes small light and dark blocks.

The problem is noticeable because I run EHT generation asynchronously to the line and frame scan. In a regular telly interference fom the LOPT is less obvious because it is synchronised to the line scan.
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Old 25th Aug 2017, 8:45 am   #4
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Default Re: The wonders of slug tape

We have a few reels of that serrated Copper tape, it certainly has uses other than zapping invertebrates. The adhesive seems to be fairly robust as it is coping outdoors thus far.

I don't know how the adhesive will cope with heat long term...but even if it becomes compromised and a short is caused one would hope that the worse you'll get is a splat, a green flash and a nasty smell (I can feel an experiment coming on)
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Old 25th Aug 2017, 2:28 pm   #5
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Default Re: The wonders of slug tape

The same stuff is sold on longer reels as EMC shielding tape. No prizes for
guessing the origins of the tape round my veg tubs in the garden
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Old 25th Aug 2017, 3:03 pm   #6
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Default Re: The wonders of slug tape

Two common sources ( amongst others) for this copper tape are the £ shops and Wilko. We've noticed that the £shop stuff has less effect on snails/slugs,as is the adhesive's longevity so perhaps similar effect for electronics.
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Old 15th Sep 2017, 8:29 pm   #7
The Philpott
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Default Re: The wonders of slug tape

I have just experimented with Cu tape across a car battery and the destruction was quick, but undramatic. I don't think there's TOO much of a worry there.
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Old 17th Sep 2017, 10:44 pm   #8
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Default Re: The wonders of slug tape

Lucky there wasn't any stray hydrogen about! That CAN be dramatic!
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Old 21st Sep 2017, 5:53 pm   #9
The Philpott
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Default Re: The wonders of slug tape

Very true, that was a bit daft really! I did get caught out once by an incinerator- (an oil drum, inevitably, with the usual holes cut in it) Having used a dribble of stale petrol as accelerant, all the fumes accumulated in the bottom and the resulting FOOMF sent all the timber i was trying to burn up to an altitude of 20'. My father managed to do the same thing 6 months later and said to me 'you'll never guess what happened the other day...'
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Old 21st Sep 2017, 6:12 pm   #10
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Default Re: The wonders of slug tape

On topic please.
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Old 22nd Sep 2017, 6:39 pm   #11
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Default Re: The wonders of slug tape

Quote:
Originally Posted by Karen O View Post
Anyway, the solution was a flux band around the LOPT and copper slug tape was just the job.
Hi Karen.

Out of interest, in what position is the flux band fitted on the LOPT? It would be good to see a pic of this put into practice. I seem to remember seeing copper tape on some types of chopper transformers in switch mode power supplies and wondered if this is for the same purpose.

Regards
Symon.
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Old 25th Sep 2017, 10:22 am   #12
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Default Re: The wonders of slug tape

Quote:
Originally Posted by The Philpott View Post
I have just experimented with Cu tape across a car battery... I don't think there's TOO much of a worry there.
Hello, I've read the thread several times but try as I might, I don't understand the relevance of , to paraphrase 'not too much of a worry there'. Not too much of a worry about what?!

Did you mean across the lugs as a trial fuse? I just don't get this at all, the use of the 'worry'
I do own reels of adhesive copper tape, however, and use it for joining sheets of copper plate as well as for screening.
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Old 28th Sep 2017, 1:29 pm   #13
Karen O
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Default Re: The wonders of slug tape

Symon,

There's a write-up and illustration here:

http://www.encyclopedia-magnetica.co....php/flux_band

Essentially, the band must not pass through the core, otherwise there will be fireworks!
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Old 29th Sep 2017, 8:59 am   #14
The Philpott
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Default Re: The wonders of slug tape

Hi Al, i meant there was no big flash or cloud of vapourising copper.. (I didn't really think there would be, but was just checking!)
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Old 29th Sep 2017, 11:14 am   #15
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Default Re: The wonders of slug tape

Hi Karen

Thanks for the link, it's an interesting read and I have learnt something new.

Regards
Symon.
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