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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment. |
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24th Apr 2013, 3:21 am | #1 |
Pentode
Join Date: Jun 2012
Location: Portsmouth, Hampshire, UK.
Posts: 206
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Fidelity record player
Hello
I have just got a Fidelity record player for which I dont know the model number. It has a BSR UA8 turntable I have looked inside it today and noticed that it has a wire wound resistor that looks burnt out!! I was wondering what I can replace this with. The amp uses 2 valves, a UY85 and a UCL84, the main smoothing capacitor is a 2 in 1 32uF and a 25uF and it also has a 0.05uF capacitor for the tone circuit which I have already replaced as it was a TCC wax capacitor and it had leaked everywhere I will post a picture of the player in question very soon but any help with that resistor would be great. Forgot to mention that there is no mains transformer, just an audio one and I don't think it's a live chassis as both wires go to the on/off volume pot. Ben |
24th Apr 2013, 7:37 am | #2 |
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Re: Fidelity record player
Hi Ben
If there is no mains transformer then it will be a live Chassis design. Cheers Mike T
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24th Apr 2013, 8:11 am | #3 |
Pentode
Join Date: Jun 2012
Location: Portsmouth, Hampshire, UK.
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Re: Fidelity record player
Hi
Here is a pic of the player Ben |
24th Apr 2013, 9:05 am | #4 |
Dekatron
Join Date: Jan 2005
Location: Oxford, UK.
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Re: Fidelity record player
To reiterate what's been said, if it's got no mains transformer, it is by definition a Live Chassis design!
The U-series valves are also a giveaway (although there are a few exceptions to that rule). The fact that both wires go to the on/off switch merely indicates it's got a double-pole mains switch, meaning that in theory, when the switch is off, the rest of the machine is completely disconnected from the mains supply. Note that the term Live Chassis doesn't actually mean that the chassis should be live. In fact, it should be connected to the mains neutral if the plug's wired correctly and the mains lead is colour-coded, meaning that if there are no faults, the chassis shouldn't present a shock risk. However, if L and N are reversed for some reason (which is not uncommon, often due to a miswired plug, miswired or non colour-coded mains lead, miswired mains socket), or if there's a break in the neutral connection, the chassis can become live, presenting a shock hazzard. Because of this, precautions must be taken, e.g. knobs must be securely fixed so that they can't be pulled off, and isolation capacitors in good condition must be in-line with the cartridge connections so that someone touching its connections doesn't get fried. If there's anything you don't understand about this, PLEASE ASK. These things are tolerably safe if you understand how they work, replace the isolation capacitors, check for faults and use common sense, but could be potentially lethal if not. An RCD plug or adaptor (as sold for lawnmowers, £4 in Wilkinsons at the moment) is a good idea. Good luck with it, Nick. P.S. My sincere apologies if you know all this already and I'm being patronising! |
24th Apr 2013, 4:10 pm | #5 |
Dekatron
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Re: Fidelity record player
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24th Apr 2013, 4:22 pm | #6 |
Dekatron
Join Date: Jan 2005
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Re: Fidelity record player
Good point, Barry, and a good 20 years newer than the rest of the machine too.
Definitely worth looking into! N. |
24th Apr 2013, 5:46 pm | #7 |
Hexode
Join Date: Jan 2013
Location: Wigan, Lancashire, UK.
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Re: Fidelity record player
I think that the original poster must be mistaken about the player having a UCL84 valve, surely that must be a UL84?
In any case, the later Fidelity HF25 will have basically the same amplifier, for which service information is available on clicking the top right hand corner. Replace the wirewound resistor with something between 120 and 150 ohms around 3 watts. |
24th Apr 2013, 7:25 pm | #8 |
Pentode
Join Date: Jun 2012
Location: Portsmouth, Hampshire, UK.
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Re: Fidelity record player
Hi
Thanks for the info!!! I didnt understand live chasis until now It was me that replaced the 2 knobs as the originals had broken It still has the original plug on it but i changed the fuse There is only 2 capacitors in the amp one being the smoothing can and the other being the 0.05uf. There is also a cap where the cartridge wires go under the turntable If i get 5 mins then i will post a pic of the amp Ben |
24th Apr 2013, 7:55 pm | #9 |
Moderator
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Re: Fidelity record player
If the control spindles are metal then you MUST NOT fit metal knobs.
If you do and the chassis goes live, you will get a shock off the knobs. If the control spindles are plastic (which I doubt) then you should be OK. |
24th Apr 2013, 8:08 pm | #10 |
Pentode
Join Date: Jun 2012
Location: Portsmouth, Hampshire, UK.
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Re: Fidelity record player
Hi
I think id better change those knobs then Does the replacement resistor have to be wirewound? Just want to be sure before i order one Ben |
24th Apr 2013, 9:49 pm | #11 |
Dekatron
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Re: Fidelity record player
If the knobs are mostly plastic with just a thin metal surface, they should be OK as long as the hole in the plastic is "blind", i.e. does not extend to the metal. If they are solid metal, you will need to change them for safety's sake.
The replacement resistor probably will have to be wirewound to withstand the power dissipation, though 2-3 watt metal film resistors are available nowadays.
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24th Apr 2013, 9:58 pm | #12 |
Pentode
Join Date: Jun 2012
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Re: Fidelity record player
Hi
Im going to change the knobs I found a 150 ohm 3 watt wirewound resistor so im going to order it now I need to change the mains lead too is it looks like a piece of string but not sure what is live and what is neutral as its not colour coded Ben |
24th Apr 2013, 10:47 pm | #13 |
Dekatron
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Location: Derby, UK.
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Re: Fidelity record player
Disconnect the player from the mains and trace the wiring from the switch. The one that goes to the chassis is the neutral, and the one that goes to the resistor and then the UY85 anode is the live.
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24th Apr 2013, 10:55 pm | #14 |
Octode
Join Date: Jul 2006
Location: Willand, Devon, UK.
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Re: Fidelity record player
According to the service manual, (which you can get from this forum by clicking the box at the very top right of this page if you haven't already) shows how the live and neutral wires should be connected to the switch. You can check afterwards with the player unplugged from the mains and with the players switch on, a resistance meter between the amplifier chassis and the neutral pin of the plug. A low reading confirms that the neutral is going the the chassis and not the live.
If your player is the same as the HF25, the diagram shows no isolation capacitors for the cartridge. That means if the chassis becomes live so do the cartridge wires! Though you do mention there is one capacitor in this location? There is a recent thread covering how to fit isolation capacitors to the pickup wiring here, they must be Class Y types. Has the old resistor actually failed? If it has really burnt out and is now open circuit this may indicate a fault in another part of the circuit. Power resistors will often get hot, sometimes very hot, during use and the heat tends to draw in dirt which can make things look worse. |
24th Apr 2013, 11:10 pm | #15 |
Pentode
Join Date: Jun 2012
Location: Portsmouth, Hampshire, UK.
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Re: Fidelity record player
Hi
I have not powered the player up yet although i have been told that it works I want to make sure that the mains plug is wired the right way. I have also replaced the 0.05uf with a modern type as the original tcc cap had leaked badly! I have just ordered the replacement resistor to be on the safe side. This is the first record player i have worked on with a live chasis, all my other repairs in the past have all had mains transformers so this one will be a challenge Ben |
25th Apr 2013, 11:13 pm | #16 |
Pentode
Join Date: Jun 2012
Location: Portsmouth, Hampshire, UK.
Posts: 206
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Re: Fidelity record player
Hi
Here is a pic of the amp Ben |
26th Apr 2013, 12:35 am | #17 |
Hexode
Join Date: Jan 2013
Location: Wigan, Lancashire, UK.
Posts: 372
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Re: Fidelity record player
Hi
Although the amplifier chassis layout is not identical, it will be similar to the HF25. The burnt resistor is the old 2 watt carbon rod type. Is the colour of it predominantly brown with one end orange? I once come across a similar amp with the same resistor smoking because of a faulty UL84 valve. Leaky smoothing capacitors could also cause this. The resistor will not have burned of it's own accord. A wirewound is better for this position as it will fuse under a fault condition. Last edited by Fidelity Fan; 26th Apr 2013 at 12:55 am. |
26th Apr 2013, 1:04 am | #18 |
Hexode
Join Date: Jan 2013
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Re: Fidelity record player
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6th May 2013, 7:30 pm | #19 |
Pentode
Join Date: Jun 2012
Location: Portsmouth, Hampshire, UK.
Posts: 206
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Re: Fidelity record player
Hi
I have changed that wirewound resistor and the 0.05uf capacitor and the player works!! The only thing is that there is a hum but you cant hear it when playing records. The hum is the same no matter the volume setting. Is this normal for this player or should i think about changing the smoothng can? Ben |
6th May 2013, 10:38 pm | #20 |
Dekatron
Join Date: May 2008
Location: Derby, UK.
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Re: Fidelity record player
It's normal to get some mains hum with these simple record players. If it disappears behind the music at a sensible volume level, then that's about the best you can hope for.
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