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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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18th Oct 2021, 10:56 am | #1 |
Triode
Join Date: Jun 2005
Location: Paisley, Renfrewshire, UK.
Posts: 24
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PYE 445U domestic shortwave
A friend has asked me if I can sort out her late father's Pye 445U. He was some sort of seagoing fellow and the multiple shortwave bandspread options are clearly designed for travellers to those far flung pink bits of the map in the 1950s. It is AC/DC with multiple voltage input options, two mains droppers one of which is open circuit and the usual UL41 etc series lineup. Unfortunately the output transformer primary is also open circuit. While I can probably unearth a spare standard OP transformer this set has a secondary winding which appears to provide negative feedback to some sort of network between the IF and the triode/DD, switched by the two gang rotary switches on the same spindle as the mains switch giving options marked F, B, M S on the front panel. I am guessing this might be some sort of audio 'tone' thing but I have no idea how to deal with that. Any suggestions? I would attach part of the circuit which I purchased from Paul Stenning but am unsure as to copyright implications.
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18th Oct 2021, 11:02 am | #2 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,966
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Re: PYE 445U domestic shortwave
You can attach a circuit fragment, but not the whole circuit.
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18th Oct 2021, 11:15 am | #3 |
Triode
Join Date: Jun 2005
Location: Paisley, Renfrewshire, UK.
Posts: 24
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Re: PYE 445U domestic shortwave
Pye 445U. Thanks. An excerpt of the circuit showing the feedback network is attached.
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18th Oct 2021, 12:20 pm | #4 |
Dekatron
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 9,433
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Re: PYE 445U domestic shortwave
A couple of members can rewind the output transformer. A request in the wanted section may help.
S2 is shown as a tone control with a ganged on/off switch for the power in the a Pye service sheet.
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Frank Last edited by Nuvistor; 18th Oct 2021 at 12:27 pm. Reason: Extra info about on/off switch |
18th Oct 2021, 1:20 pm | #5 |
Heptode
Join Date: Mar 2017
Location: Romsey, Hampshire, UK.
Posts: 524
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Re: PYE 445U domestic shortwave
Hi
My best guess at the meanings is: F = Fidelity (Flat Response) B = Bright (Treble Boost) M = Mellow (Treble Cut) S = Shortwave (Bass and Treble Cut) |
18th Oct 2021, 1:59 pm | #6 |
Dekatron
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,578
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Re: PYE 445U domestic shortwave
These are good sets. Well worth getting the output transformer rewound. Slight oddity which caught me out....the high frequency end of MW (200 metres) starts at the low-frequency end of the Trawler band....if that makes sense? I thought that MW was slightly off tune since I like to listen to Capital Gold on 194 metres but for some reason, MW only tunes down to 200 metres. The Trawler band however starts at 200 metres and Capital Gold can be found just below that mark.
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18th Oct 2021, 2:59 pm | #7 |
Pentode
Join Date: Nov 2020
Location: Bristol, UK.
Posts: 132
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Re: PYE 445U domestic shortwave
This is a clever tip from the late Chas Miller. If you have a standard output transformer and wish to avoid the cost of rewinding the original, you can fit the standard one in the normal way and use the original as well for the feedback circuit. Simply ignore the o/c primary, leave the feedback winding in circuit, and connect the speaker secondary winding to the secondary of the "new" transformer observing the correct phasing of course.
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25th Oct 2021, 4:40 pm | #8 |
Triode
Join Date: Jun 2005
Location: Paisley, Renfrewshire, UK.
Posts: 24
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Re: PYE 445U domestic shortwave
Thanks for all those contributions.
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