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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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18th Sep 2008, 9:56 am | #1 |
Octode
Join Date: Oct 2005
Location: Wimborne, Dorset, UK.
Posts: 1,407
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Advice needed with Philips B6X12A
Hi all,
I have the above set, (I think the model No. is right) It is a stereo set (on gram input anyway) The set uses 800ohm speakers! The output valves are 2 EL84's (one per channel) The problem is that one of the speakers is U/S, the voice coil is grating on the magnet and there is no adjustment that I can see, I no it wont be original but can I simply replace the output transformers so that coventional low impedance speakers can be used? Many thanks Lee
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Lee |
18th Sep 2008, 10:12 am | #2 |
Octode
Join Date: Aug 2003
Location: Welwyn Garden City, Herts. UK.
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Re: Advice needed with Philips B6X12A
Are You sure it uses output transformers, as usually the high impedance speaker is used to avoid the need for them.
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18th Sep 2008, 10:28 am | #3 |
Retired Dormant Member
Join Date: Jul 2005
Location: West Yorkshire, UK.
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Re: Advice needed with Philips B6X12A
Hi Lee,
Since the schematic isn't available from Paul Stenning, here's a link to one, (320k .pdf) It does use transformers but the primaries are tapped, so replacing them is not necessarily quite as straightforward as it could be. One thought crossed my mind, it'd be possible to wind a couple of autotransformers to match low-impedance speakers to the set. That'd leave the output stage circuitry undisturbed making it easier to return the set to original should a replacement high-impedance speaker be found at a later date. Cheers, Kat |
18th Sep 2008, 11:52 am | #4 |
Dekatron
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,580
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Re: Advice needed with Philips B6X12A
This sounds like a variant of the 'Reverbeo'. I restored a similar set of the 'bi-ampli' type that used small output transformers with 800 ohm speakers. Before you condemn the speaker, check that the corrugated suspension disk (that attaches to the cone) hasn't come adrift. If it has, you can use something like Evo-Stik sparingly to glue it back into place. I've done this a number of times with good results.
Rich.
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18th Sep 2008, 1:30 pm | #5 |
Octode
Join Date: Oct 2005
Location: Wimborne, Dorset, UK.
Posts: 1,407
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Re: Advice needed with Philips B6X12A
Hi All,
Thanks for the replies, Rich I have had the set completely to bits and the speakers were taken out. They are in very good condition and it is definitely the voice coil scraping on the magnet. Kat, I like your idea would that be just a small number of turns of wire around the core? How many? I'm posting a request for a replacement speaker in the relevant section. Cheers Lee
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18th Sep 2008, 1:42 pm | #6 |
Nonode
Join Date: Jun 2004
Location: Norwich, Norfolk, UK.
Posts: 2,543
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Re: Advice needed with Philips B6X12A
Hi Lee,
Try twisting the speaker frame gently with your hands, whilst playing, and see if you can get any improvement. David |
18th Sep 2008, 3:55 pm | #7 | |
Retired Dormant Member
Join Date: Jul 2005
Location: West Yorkshire, UK.
Posts: 1,700
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Re: Advice needed with Philips B6X12A
Hi Lee,
Quote:
To me, making a couple of autotransformers seems like the obvious answer, you don't need isolation as the existing transformers provide that. There's less wire to wind as there's only one winding involved, too. I like to avoid modifying things if possible. So redefining the problem as "how can I match a modern 8-ohm or 4-ohm speaker to a set which expects an 800-ohm speaker" is what I'd be looking into if this was my set. (I'd probably look for a pair of car speakers which would fit.) Cheers, Kat |
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