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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment. |
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3rd Oct 2019, 11:16 am | #21 |
Dekatron
Join Date: Jun 2013
Location: East Sussex, UK.
Posts: 3,326
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Re: Weird circuit in Fidelity record player.
Often the sellers of items don't have an engineer's knowledge of these matters. If it has two transformers then they think it's a full mains transformer, but it's not always so.
Descriptions are often wrong on auction sites. |
3rd Oct 2019, 11:18 am | #22 |
Heptode
Join Date: Aug 2011
Location: Bristol, UK.
Posts: 538
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Re: Weird circuit in Fidelity record player.
The one that I'm working on definitely doesn't have a mains transformer but it does have two transformers which at first led me to believe that it did have a mains transformer.
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3rd Oct 2019, 11:28 am | #23 |
Nonode
Join Date: Nov 2016
Location: Aberaeron, Ceredigion, Wales, UK.
Posts: 2,884
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Re: Weird circuit in Fidelity record player.
I completely agree, any chance of a picture ?
Cheers John |
3rd Oct 2019, 2:02 pm | #24 |
Heptode
Join Date: Aug 2011
Location: Bristol, UK.
Posts: 538
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Re: Weird circuit in Fidelity record player.
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3rd Oct 2019, 2:12 pm | #25 |
Nonode
Join Date: Nov 2016
Location: Aberaeron, Ceredigion, Wales, UK.
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Re: Weird circuit in Fidelity record player.
Ok ta, just thought it would be interesting to see amp.
Cheers John |
3rd Oct 2019, 4:40 pm | #26 |
Dekatron
Join Date: Sep 2015
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Re: Weird circuit in Fidelity record player.
Well it does have a Mains transformer now if there are 2 transformers there....
With photos, we can tell if it is for the filaments only or if it is double-wound and therefore offers an isolated chassis.
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Edward. |
3rd Oct 2019, 11:15 pm | #27 | |||
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Re: Weird circuit in fidelity record player.
Quote:
I do hope it was an isolated chassis, otherwise God help the buyer. Quote:
Quote:
Especially if its like the circuit described in post #10 But they weren't available till around 1960, starting with I think the UA12. |
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4th Oct 2019, 7:49 am | #28 |
Dekatron
Join Date: Sep 2015
Location: Southwold, Suffolk, UK.
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Re: Weird circuit in fidelity record player.
My point in Post #26 is that if it were just a filament transformer (autotransformer) one would expect to see just 4 winding connections, and if isolated, then at least 5.
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Edward. |
4th Oct 2019, 9:11 am | #29 |
Dekatron
Join Date: Jun 2013
Location: East Sussex, UK.
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Re: Weird circuit in Fidelity record player.
Should be able to tell from a photo as an isolated type will have 3 windings and heater only just 2. There might be a snag if there are extra tags for a primary tap for 200 and 240 volts but that would be rare in this type of player.
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6th Oct 2019, 9:56 am | #30 |
Heptode
Join Date: Aug 2011
Location: Bristol, UK.
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Re: Weird circuit in Fidelity record player.
Hello guys,
I'm away from Bristol for a few days but as far as I can recall the transformer has 4 taps. Many thanks |
6th Oct 2019, 11:35 am | #31 |
Dekatron
Join Date: May 2008
Location: Derby, UK.
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Re: Weird circuit in Fidelity record player.
It would need to have 5 or 6 connections to provide isolation: two for mains in, two for HT out and two for LT out, but one end of the LT and one end of the HT secondary windings could be joined giving just 5 connections. Four connections suggests just mains in and LT out, with the mains being used directly to supply the HT.
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If I have seen further than others, it is because I was standing on a pile of failed experiments. |
16th Oct 2019, 12:13 pm | #32 |
Heptode
Join Date: Aug 2011
Location: Bristol, UK.
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Re: Weird circuit in Fidelity record player.
Hi,
These are the photos of the amplifier the 6x4 is hooked up directly to the mains and for some reason the 6x4's keep dying. I will be changing the plessey before anyone mentions it. Many thanks. |
16th Oct 2019, 12:58 pm | #33 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
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Re: Weird circuit in Fidelity record player.
According to the rectifier's valve data Rs should be around 180 ohms minimum per anode so far as I can make out for 240 volt mains.
Lawrence. Last edited by ms660; 16th Oct 2019 at 1:14 pm. Reason: correction and addition |
16th Oct 2019, 3:48 pm | #34 |
Nonode
Join Date: Nov 2016
Location: Aberaeron, Ceredigion, Wales, UK.
Posts: 2,884
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Re: Weird circuit in Fidelity record player.
Looking at your pictures it looks like there is a wire bridging across the Mains terminal on the transformer, or inadvertently shorting, I could be completely wrong of course! A few more pictures would be useful.
Cheers John |
10th Mar 2020, 8:57 am | #35 |
Octode
Join Date: Feb 2007
Location: Ely, Cambridgeshire, UK.
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Re: Weird circuit in Fidelity record player.
Just had one off these come my way to sort. Thread here:-
https://www.vintage-radio.net/forum/...d.php?t=164635 |
10th Mar 2020, 10:15 am | #36 | |
Rest in Peace
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Location: Basildon, Essex, UK.
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Re: Weird circuit in Fidelity record player.
Quote:
The first valve was obviously no good, the second valve may have had a fault in it. Test the smoothing caps for electrical leakage. With the EL84 valve removed there should be next to no current on the path from the rectifier cathode to the first smoothing capacitor. (once the caps are charged up) To measure this connect your ammeter via a 10k resistor in series with the HT circuit before the rectifier. There will be a high initial current, (25mA) but if after 60 minutes there is still more than 1mA flowing, replace the capacitor with a new one. Be careful as you are working with live mains. Mike |
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10th Mar 2020, 10:38 am | #37 | |
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Re: Weird circuit in Fidelity record player.
[QUOTE=crackle;1224082]
Quote:
There'll be two fuses in series. One in the lamp limiter's plug and one in the player's plug. Either or both could blow.
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Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
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