PYE 445U domestic shortwave - UK Vintage Radio Repair and Restoration Discussion Forum

chas · 18th Oct 2021, 10:56 am

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.

paulsherwin · 18th Oct 2021, 11:02 am

You can attach a circuit fragment, but not the whole circuit.

chas · 18th Oct 2021, 11:15 am

Pye 445U. Thanks. An excerpt of the circuit showing the feedback network is attached.

Nuvistor · 18th Oct 2021, 12:20 pm

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.

Mr 1936 · 18th Oct 2021, 1:20 pm

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)

Sideband · 18th Oct 2021, 1:59 pm

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.

radiomobile · 18th Oct 2021, 2:59 pm

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.

chas · 25th Oct 2021, 4:40 pm

Thanks for all those contributions.

18th Oct 2021, 10:56 am	#1
chas Triode Join Date: Jun 2005 Location: Paisley, Renfrewshire, UK. Posts: 24	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.

18th Oct 2021, 11:02 am	#2
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,947	Re: PYE 445U domestic shortwave You can attach a circuit fragment, but not the whole circuit.

18th Oct 2021, 11:15 am	#3
chas Triode Join Date: Jun 2005 Location: Paisley, Renfrewshire, UK. Posts: 24	Re: PYE 445U domestic shortwave Pye 445U. Thanks. An excerpt of the circuit showing the feedback network is attached. Attached Thumbnails

18th Oct 2021, 12:20 pm	#4
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,433	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. __________________ 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
Mr 1936 Heptode Join Date: Mar 2017 Location: Romsey, Hampshire, UK. Posts: 521	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
Sideband Dekatron Join Date: Oct 2003 Location: Croydon, Surrey, UK. Posts: 7,572	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. __________________ There are lots of brilliant keyboard players and then there is Rick Wakeman.....

18th Oct 2021, 2:59 pm	#7
radiomobile Pentode Join Date: Nov 2020 Location: Bristol, UK. Posts: 132	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.

25th Oct 2021, 4:40 pm	#8
chas Triode Join Date: Jun 2005 Location: Paisley, Renfrewshire, UK. Posts: 24	Re: PYE 445U domestic shortwave Thanks for all those contributions.