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Success Stories If you have successfully repaired or restored a piece of equipment, why not write up what you did and post details here. Particularly if it was interesting, unusual or challenging. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

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Old 15th Mar 2016, 5:25 pm   #1
vinrads
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Default Strange fault cured!

The problem was on a Emerson 888 transistor radio this the one with pre set L/W having replaced all the usual capacitors and a re alignment of the i,f 's all was fine until it was fitted in it's case then the LW disappeared.
This was found happen only when the battery pack was fitted it fits close to the osc coil ,strange thing the osc coil had no screening can but the IF's had , a screen was tried on the osc coil but it did not like this at all,no amount of adjusting would bring it back on freq ,then I noticed that the slug was at the bottom of the coil,a quick tweak to the top with the batteries in brought back the L/W.
Had it been got at ? but it cured the problem a re alignment of the RF circuits all is working fine now . Mick.

Last edited by vinrads; 15th Mar 2016 at 5:36 pm.
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Old 15th Mar 2016, 9:20 pm   #2
Skywave
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Arrow Re: Strange fault cured!

No - I don't believe it had been 'got at' - in the sense that you're thinking. But let's summarily re-cap on what you have reported.

1. The osc. coil is not screened. (Which I admit, is unusual).
2. When you introduced a screen, the osc. coil 'did not like it'.
3. When the batteries were inserted, the problem arose: the coil 'did not like it'
4. With the set out of the case - and the batteries thus not in close proximity to the osc. coil and no additional screen fitted - all was O.K.

Sounds to me that the batteries - containing metal and probably the outer case, being at 'ground' potential - were de-tuning the osc. coil. Ditto with the additional screen that you tried.

So it seems to me that that set has only been 'got at' in that sense.

But the important thing is that the entire job is now a 'success story': well done.

Al.
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Old 15th Mar 2016, 9:31 pm   #3
vinrads
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Default Re: Strange fault cured!

Hi thank,s for the reply I realise the osc was being de tuned due to the batteries but why was the osc never fitted with a screening can ?
The reason I suggested that it had been got at was because all the other coils had there slugs at the top! Mick.
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Old 16th Mar 2016, 12:38 pm   #4
Skywave
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Arrow Re: Strange fault cured!

No screening can: why? Regretfully, I have no idea! And you comment that the tuning slugs were at the limit of their travel. Now not wishing to sound rude nor unjustifiably derogatory, but somehow that observation and the 'missing' osc. coil screening can does seem to throw a doubt over the quality of the design of that unit.
But it's the end result that matters most of all - and in this case, that result - for you - was a success.

Al.
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Old 16th Mar 2016, 2:38 pm   #5
G6Tanuki
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Default Re: Strange fault cured!

What kind of batteries? A lot of transistor-radio batteries in the 1950s/1960s/1970s had a cardboard outer-case over either 'layer' calls or a Zinc-Carbon construction - no ferrous metal so any detuning would be limited.

Modern ferrous-metal-cased batteries would have much more of a detuning effect.
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