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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc. |
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7th Jul 2019, 2:43 pm | #1 |
Pentode
Join Date: Aug 2009
Location: Portsmouth, Hampshire, UK.
Posts: 230
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Philips 492U aerial connectivity
Hello All,
I'm slowly restoring this 1949 Philips 492U. Coming along nicely and now at the point where I need to get out the Aurora and squirt a signal in. The set uses a balanced twin-feeder arrangement (no co-axial socket) and I haven't encountered a set with this arrangement for over 20 years. Embarrassingly I have completely forgotten how to connect it up and I can't find any information on how to do this anywhere. Do I need a balance to imbalance transformer (which I do not possess) or is there another way? Seem to remember making something up with 1000pf caps but it was all a long time ago. Best regards Matt Last edited by matspar; 7th Jul 2019 at 2:51 pm. |
7th Jul 2019, 3:35 pm | #2 |
Tetrode
Join Date: Sep 2017
Location: Waalre, Netherlands
Posts: 67
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Re: Philips 492U aerial connectivity
Hi Matt,
that is a very neat 492U you have! Would be interested in some more detailed pictures, also for my site on the early Philips TV history. As to a 75 Ohm asymmetrical to 300 Ohm symmetrical converter, below is just one of the many examples you can find. I don't think it is very critical in this case. Attached is a schematic of the input of the 485U, which is the same as in the 492U, so you can tune the antenna out with C18 for maximum reception. Cheers, Pieter |
7th Jul 2019, 5:37 pm | #3 |
Hexode
Join Date: Mar 2014
Location: Dublin, Ireland
Posts: 398
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Re: Philips 492U aerial connectivity
75-300 ohm balun matching transformers are available very cheaply on ebay if you don’t wish to make up one yourself - the added advantage being that they come fitted with appropriate connectors for such as your application, that is if you get the appropriate one
Alternatively you can ground one side of the TVs input transformer and connect Aurora directly (assuming tv chassis is grounded, which I believe it is) |
8th Jul 2019, 12:39 am | #4 |
Pentode
Join Date: Aug 2009
Location: Portsmouth, Hampshire, UK.
Posts: 230
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Re: Philips 492U aerial connectivity
That's a great help very many thanks Gents! I will probably go for one of the Ebay ones just for the ease of fitment. Pieter here are a few pics to give you an idea. How rare is the 492U? I can't seem to find another example online.
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19th Jul 2019, 9:01 pm | #5 |
Tetrode
Join Date: Sep 2017
Location: Waalre, Netherlands
Posts: 67
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Re: Philips 492U aerial connectivity
Hi Matt,
thanks a lot for the pictures! A very nicely restored set you have. I suppose the last two pictures are before and after restoration? Was the MW31-74 sticker on the picture tube original? It's a picture tube code I've never seen. The standard tube for the 492U was the MW31-14C, later the MW31-17 and -18. So in any case this looks like a replacement tube. As to the uniqueness of your set: I think it is very rare. Although I'm always surprised to see how old sets turn up unexpectedly, I haven't seen any so far and I'm not aware of the existence of others. All I have are pictures from old Philips advertisements, so yours are the first of a real set. I might use one of them on my site if you don't mind. Regards, Pieter |
20th Jul 2019, 5:26 pm | #6 |
Dekatron
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 7,444
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Re: Philips 492U aerial connectivity
The 441 line Philips TF402A is very similar in appearance to the model 492U.
https://radio-piffret.pagesperso-orange.fr/TV.htm https://radio-piffret.pagesperso-ora...402A29_doc.jpg The TF402A has a mains transformer and the HT rectifier is an AX50. DFWB. |
22nd Jul 2019, 3:15 pm | #7 |
Dekatron
Join Date: Dec 2007
Location: Haarlem, Netherlands
Posts: 4,203
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Re: Philips 492U aerial connectivity
Very nice to see more of those old sets!
To possibly determine the history of the MW31-74 in this set, could you have a look at the factory code? It's 2 lines of a few characters just as on normal valves, but it can be located either on the socket or stamped on the cone. It should contain a date code. |
22nd Jul 2019, 3:29 pm | #8 |
Heptode
Join Date: Jun 2006
Location: Eindhoven, Netherlands.
Posts: 642
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Re: Philips 492U aerial connectivity
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26th Jul 2019, 11:11 am | #9 |
Nonode
Join Date: Jun 2009
Location: Herefordshire, UK.
Posts: 2,495
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Re: Philips 492U aerial connectivity
I wonder what balanced input aerial impedance Philips designed the set for?
300 Ohm was a USA standard, but I believe the Germans and others used 240 Ohm and some UK set makers used 75 Ohm. Finally, 75 Ohm unbalanced was adopted in the UK and with the widespread use of Cable TV, 75 Ohm unbalanced became the norm elsewhere. |
31st Jul 2019, 1:23 am | #10 |
Pentode
Join Date: Aug 2009
Location: Portsmouth, Hampshire, UK.
Posts: 230
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Re: Philips 492U aerial connectivity
Thanks everyone for your interest and replies. I fitted the MW31-74 as the original MW31-14c had an o/c heater due to a past heater chain bodge.
I have since rebuilt the chassis and the reciever is now producing pictures and performing very well. It required a lot of work, apart from the replacement crt I replaced all of the pitch covered capacitors and most of the electrolytics which were all suffering from severe leakage. Many were also dead short. Very interested to learn about the rarity of this set. Could this be the only one of its type left in existence I wonder? internally it is dated Nov 1949. Here are some photos of the finished chassis. I am currently restoring the cabinet which needs some refinishing mainly to the curved front surround. The rest should repolish quite well and retain the original finish. |