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Old 2nd Oct 2015, 7:02 am   #1
happytiger
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Default Fitting a three core flex?

SPLIT FROM THIS THREAD:-

https://www.vintage-radio.net/forum/...ad.php?t=22531


You should also ensure that safety is restored to mfr specs, no bodges or "updated safety"mods.
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Old 2nd Oct 2015, 10:59 am   #2
DonaldStott
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Default Re: Test equipment for valve radio repair

Quote:
Originally Posted by happytiger
You should also ensure that safety is restored to mfr specs,no bodges or "updated safety"mods
Thanks for the comprehensive list of Test equipment I should be looking at long term...

In the interim I'm unsure what you mean by "You should also ensure that safety is restored to mfr specs,no bodges or "updated safety"mods"

I intend to replace the existing two core flex with a modern three core power cord with an inline fuse and use one of the tags on the chassis as an earth?

Last edited by DonaldStott; 2nd Oct 2015 at 11:02 am. Reason: Typo
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Old 2nd Oct 2015, 11:08 am   #3
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Default Re: Test equipment for valve radio repair

Quote:
Originally Posted by DonaldStott
I intend to replace the existing two core flex with a modern three core power cord with an inline fuse and use one of the tags on the chassis as an earth?
Be careful. You say the set is a 1956 Philips. It may have a dropper resistor and a live chassis or it may have an auto transformer and a live chassis. In neither case should you fit a three core mains lead.
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Old 2nd Oct 2015, 11:31 am   #4
DonaldStott
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Default Re: Test equipment for valve radio repair

Thanks Graham - I appreciate you pointing out the safety concerns.

I'm taking my lead from this post: -

https://www.vintage-radio.net/forum/...ad.php?t=30724

Howard states - "...and lastly fitted a new 3 core mains lead and this set has an earth tag already in place on the mains lead tag board on the top of the chassis."

And also this link: -

http://www.vintage-radio.com/recent-...ps-b3g63a.html

Tim states - "A length of white two core cable had been fitted which would have to be changed to 3 core, as this is an A/C only set." and "The new mains cable was fitted, the L and N conductors soldered directly to the switch (which is possible-just!) and the earth soldered to a nearby chassis tag."

The chassis tag referred to looks like this: -

Click image for larger version

Name:	Earth_Tag.jpg
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ID:	113716

(P.S. The chassis has been thoroughly cleaned after this picture was taken and is now pristine.)

I've not come across any reference to a LIVE chassis for this Philips radio but if anyone has information to the contrary it would be most welcome - many thanks.
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Old 2nd Oct 2015, 11:53 am   #5
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Default Re: Test equipment for valve radio repair

The Philips B3G63A has a proper mains transformer, so is not a live chassis design.
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Old 2nd Oct 2015, 12:27 pm   #6
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Default Re: Test equipment for valve radio repair

Thanks Graham for the quick response- that's put my mind at rest.
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Old 4th Oct 2015, 2:32 pm   #7
happytiger
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Default Re: Test equipment for valve radio repair

Quote:
Originally Posted by DonaldStott View Post
In the interim I'm unsure what you mean by [I]"You should also ensure that safety is restored to mfr specs,no bodges or "updated safety" mods"
The mains flex should only be replaced if its faulty or unsafe. You dont fit 3 core leads on 2 core sets.! Connecting chassis to mains earth is not a good idea (from a radio point of view) besides the hazard of multiple earth connections, (I will not go in to the technicalities here). As I mentioned no "updated safety mods" you are to aim for originality.
If you must fit 3 core lead, take the earth to a wander plug and connect to the earth socket, this is the only earth connection you should make.
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Old 4th Oct 2015, 2:55 pm   #8
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Exclamation Re: Test equipment for valve radio repair

Quote:
Originally Posted by happytiger View Post
You don't fit 3 core leads on 2 core sets.! Connecting chassis to mains earth is not a good idea (from a radio point of view) besides the hazard of multiple earth connections, (I will not go in to the technicalities here). As I mentioned no "updated safety mods" you are to aim for originality.
If you must fit 3 core lead, take the earth to a wander plug and connect to the earth socket, this is the only earth connection you should make.
Sorry, my friend, but most of that I simply cannot agree with.

If the set has a mains isolating transformer fitted to a metal chassis, then connecting the metal chassis to supply earth is a good idea. One reason being that such a mains transformer may have an electrostatic screen between primary and secondary. Amongst other reasons, this needs to be connected to mains earth for safety reasons.

Hazards arising from multiple earth connections are a matter of how the various mains leads are arranged where those mains leads connect to the wall-mounted supply socket(s) - so not a consideration of the wiring to (and within) the set itself.

As for connecting the in-coming mains earth to the set's 'earth' socket via a wander plug, that really is a bad idea! Suppose the wander plug falls out? Besides, the set's 'earth' socket is for connecting an 'R.F.' earth, not the mains supply earth! Doing what you suggest will could easily create various ' technical' (and safety) problems.

Finally, "aiming for originality" is simply a choice to be made by the item's owner - there are no rigid rules on this - provided that electrical safety is not compromised.

Al.
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Old 5th Oct 2015, 11:14 am   #9
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Default Re: Test equipment for valve radio repair

So I now have two completely opposite views on replacing the existing two core lead with a modern three core lead - my original plan was to also fit an inline fuse e.g. 800mA anti-surge, and to solder the earth wire to the tag on the chassis.

Previous posts on this make and model of Philips radio had all fitted a three core lead and the post from Station X above clearly stated that "The Philips B3G63A has a proper mains transformer, so is not a live chassis design."

As a "beginner" I have no means of making a judgement call here but I would tend to go with my instinct which is telling me that using a three core lead and earthing it to the chassis is the correct way to go? I have no idea what the "the technicalities" are here or the suggested use of a wander plug (what's that?) - I naively thought that there would be general agreement on this point??

I am not "aiming for originality" but interested in doing a "restoration" to get this radio back up and working to the best of its ability - it is for my own personal use.

Last edited by DonaldStott; 5th Oct 2015 at 11:19 am. Reason: Missed a sentence
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Old 5th Oct 2015, 11:26 am   #10
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Default Re: Test equipment for valve radio repair

For your own personal use, it's your life and your choice. If the set gets back into the wild, in today's litigious world, original (suitable replacement parts excepted) is least likely to result in your being peered at by the beak and asked to justify your "improvements".

Fitting a new plug of the RCD variety is useful braces and isn't a modification to the set.
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Old 5th Oct 2015, 11:36 am   #11
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Default Re: Test equipment for valve radio repair

Donald.

I'm afraid you will get conflicting advice in these forums, especially where the question as to whether to fit a three core mains lead to a set not having a live chassis is concerned. The subject has been discussed in several forum threads and no consensus has been reached.

After weighing up the facts and opinions you'll have to make up your own mind what to do.
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Old 5th Oct 2015, 11:57 am   #12
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Default Re: Test equipment for valve radio repair

As Graham says, there are many areas of vintage radio restoration where there are genuinely divided opinions, such as whether it is good practice to change all the old wax caps in a set without testing them. Usually there is a majority view but a strongly held minority view. All you can do is decide for yourself, though I appreciate this is difficult for a beginner.

In this case it is definitely the majority view that sets with transformers should be fitted with a 3 core cable earthing the chassis, as this makes the radio much safer in the event of a fault condition, and this is what I do. Not everyone will agree though.
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Old 5th Oct 2015, 12:07 pm   #13
DonaldStott
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Default Re: Test equipment for valve radio repair

Thanks guys for all your support and helpful advice - I appreciate that at the end of the day t's my choice but I now have a clearer idea of what I'm going to do.

I'll report back, even if things end with a loud bang and a puff of smoke!

I also appreciate that this thread (Test equipment for valve radio repair) has gone off at a bit of a tangent so here's another question to get it back on track - what can I do in the way of (meaningful) valve testing with just a DMM and a 3V continuity tester??

Last edited by DonaldStott; 5th Oct 2015 at 12:17 pm. Reason: Missing word
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