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Old 25th Jul 2004, 10:12 pm   #1
yestertech
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Default Removing /loosening IFT slugs

Anyone got any top tips for removal /loosening ( for alignment purposes ) IFT slugs from the cores of the transformers on the 50's style components? Many times I have had a slug which stubbornly refuses to budge, despite prior removal of wax or paint. With the flimsy construction of the more modern units , it pays not to be too heavy handed !!!
Breaking open discarded ones often reveals the slug to have virtually welded itself to the screwed thread of the former. Similarly, what is a foolproof way to remove the paint or wax in the first place. ?? ( maybe just " leave well alone " ??)
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Old 25th Jul 2004, 11:03 pm   #2
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Default Re: Removing /loosening IFT slugs

Have you tried Acetone (nail varnish remover)?

Chris
 
Old 25th Jul 2004, 11:07 pm   #3
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Default Re: Removing /loosening IFT slugs

Andy, Ear wax remover (Earex) is good for shifting cores locked with wax or Rocol core locking compound (black gunge).

For the white paint used by Bush in the later sets, use acetone (nail varnish remover).

In either case, apply a few drops and wait several minutes, especially with well hardened wax. Then screw the core gently inwards, making sure you use the proper tool with a flat blade. A screwdriver will usually break a ferrite or dust core, due to the blade being tapered.

Regards, Leon.
 
Old 26th Jul 2004, 8:09 am   #4
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Default Re: Removing /loosening IFT slugs

I've also used a hairdryer when slugs have been particularly stubborn. Gentle even heating is best.

I like the Earex suggestion...not tried that. Nail varnish remover could be a bit dodgy with some plastics I think.

Rich.
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Old 26th Jul 2004, 10:53 am   #5
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Default Re: Removing /loosening IFT slugs

Thanks for the suggestions guys - I have used acetone with success, but as Richard says, I am slightly worried what it might do to the plastic former. The ear drops do seem to work on the wax sealed units, but again, sometimes even with a " clear view " of the slug, they do not budge! The worst case I had was in a Murphy, where the slugs had hex slots and even with exactly the right Hex key, the slugs still did a self detsruct, as they had virtually 'fused' to the former - As to the right tool, I am guilty of using said screwdriver, but the trimming tools from MAPLIN are so useless they break at the slightest strain. Anyone point me at a good source of trimming tools ?? ANDY
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Old 26th Jul 2004, 11:59 am   #6
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Default Re: Removing /loosening IFT slugs

One suggestion about jammed slugs is that with heat from the radio, the coil formers 'shrink' slightly over time with the result that the core is firmly jammed. Some coil formers are better than others in this respect and I suspect it is due to the material they are made from.

Under these conditions, it is difficult to know exactly what to do as removal of wax or paint is unlikely to free the core. I had an experience like this with a Pilot 'Little Maestro' that I restored. Being a 'midget' AC/DC set, it had obviously run quite hot over the years and when I did a re-alignment, one core was jammed solid and no amount of heating or other methods would free it. In the end I left it alone as IF alignment was almost spot-on with the other cores. Interestingly, the jammed core was in the transformer nearest the output valve.

So I think the choice is yours. Either leave it on the assumption that it won't have drifted or break it out and use another core from a scrap transformer. However in doing this you may find that the replacement core sticks where the former has shrunk....!

Rich.

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Old 26th Jul 2004, 1:58 pm   #7
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Default Re: Removing /loosening IFT slugs

Richard and Tony - thanks for the thoughts ! I am with you regards " leave well alone " if stuck, as for most AM sets it won't matter over much - However, when the core is in an FM IFT and if it's the discriminator, its good to know one can adjust to get them 'spot on' . Maybe I just need to stop chasing perfection !! ANDY
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Old 26th Jul 2004, 6:25 pm   #8
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Default Re: Removing /loosening IFT slugs

I had a Murphy A170 in which all of the IF cores were eventually freed - except one.

In this situation, the remedy is easy. De-tune the free cores, then peak the stuck transformer winding to its resonant frequency by swinging the generator. Then align the rest of the set to this frequency. The actual IF frequency is not too critical, but it is obviously necessary to have all of the tuned circuits in resonance together - unless the design uses stagger tuned circuits.

The old dog of a Murphy aligned perfectly giving excellent results and good sound (once the 'speaker had been centred) for a standard superhet.

Regards, Leon.
 
Old 17th Aug 2004, 12:20 am   #9
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Default Re: Removing /loosening IFT slugs

And here's one for Real Men...

"Instructions for releasing the cores are as follows :
1. Iron Dust Cores (large). Soak a piece of cotton wool in methylated spirit and place on top of the core. Set light to it and allow it to burn out. The core should now be eased gently. If it is still tight, repeat the process. [...]"

(From 'The R1155 Communications Receiver' Practical Wireless, June 1957, p.258.) Honest!

Neil F.

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