Information about the company Fidelity

[plumbweiss]

Just looking at the WWW, Caparo started buying all Fidelity PLC's shares in 1984 but started legal proceedings against the auditing accountants for Failure of Duty of Care, resulting in a high court trial in 1990, the proceedings involved Nigel Lawson at one point and the defendants were found not guilty.

The case is well covered on the WWW and seems to be used alot as an example in law studies!

[gloves86]

Does anyone know if this would have used a shaded-pole motor or an induction motor?

Thanks

[llama]

I don't know the answer to the motor question (though I do have 2 of these decks around somewhere - one of them 60Hz) but thinking about the motor raises some points about value-engineering that was commonplace at that time.

The whole of the innards was live to one side of the mains (in a similar way to "AC/DC" receivers) and the valve heaters were typically fed from a tapping on the winding on the motor. So it was used as an auto-transformer rather than having the expense and heat of a dropper resistor.

In later times, the decks were made even cheaper by using direct drive/DC motors, but that was when transistor amplifiers were the norm (and so a supply of DC was already available).

Hope this helps with the engineering side of your query.
Graham

[Herald1360]

Originally Posted by gloves86

Does anyone know if this would have used a shaded-pole motor or an induction motor?

Thanks

A shaded pole motor IS an induction motor- it gets the rotating field necessary for starting a single phase motor by a shorted turn around part of one of the lamination stack poles (this "shades" the pole). This causes a phase shift in the field in that part of the pole.

I suspect you may be thinking about a synchronous motor as the alternative to shaded pole- it's highly unlikely that a cheap record player would have a synchronous motor, they are more in the province of a transcription turntable!

The operational difference is that a synchronous motor runs at a speed directly locked to the AC supply whereas the induction motor (of whatever sort) runs at a slightly lower speed. If you overload a synchronous motor it simply stops, an induction will slow down and deliver a greater torque up to a point, then it will stall.

Hope this helps.

Chris

[gloves86]

oh ok...induction motor it is then! thanks This is a bit more of a technical question, but I'm trying to figure out how the LP player actually works...here's what I understand so far:

1) The mechanical movement of the stylus in the grooves of the record (i.e. the vibrations) travel up to the piezo-electric crystal (probably a ceramic cartridge) and create a voltage by stressing the crystal

2) The signal travels to the valve amplifier, which works by using a heater at the anode end of the valve, which creates a stream of negatively charged electrons. These electrons are attracted to the opposite end of the valve by the cathode plate. There is a plate in the centre of the valve whose charge is determined by the input signal from the piezo-electric crystal. The changing charge on this centre grid determines how many electrons are ‘allowed’ through, and therefore the output signal is identical to the input signal apart from the fact that it has been amplified by the use of the electron generator.

This is where I get a bit stuck....

3) The amplified signal travels to the rectifier which converts AC to DC...this then goes to the capacitor which apparently blocks all DC! The way I understand it is that when the rectifier changes AC to DC it isn't a 'smooth' signal...so this is what the capacitor does (removes distortion). The rectifier keeps the capacitor 'topped up' with +ve charge which is transmitted to the loudspeaker...

Sorry if I've made stupid mistakes, but shall we just say electronics really aren't my strong point!

Here's a picture of the components under the board...I would be so grateful if someone could explain to me how it works!

http://img.photobucket.com/albums/v6..._0508Large.jpg

Thank you.

Rachael.

[Station X]

2) The signal travels to the valve amplifier, which works by using a heater at the anode end of the valve, which creates a stream of negatively charged electrons. These electrons are attracted to the opposite end of the valve by the cathode plate. There is a plate in the centre of the valve whose charge is determined by the input signal from the piezo-electric crystal. The changing charge on this centre grid determines how many electrons are ‘allowed’ through, and therefore the output signal is identical to the input signal apart from the fact that it has been amplified by the use of the electron generator.

Actually the heater is at the cathode end of the valve, the cathode being connected to the -ve side of the supply. I always think of electrons being boiled off the cathode and then being attracted to the anode which is connected to the postive side of the supply. I know that this means current flowing from -ve to +ve, which is the opposite to conventional wisdom, but thats how I think of valve operation.

The valve doesn't actually generate any electrons. They're supplied by the power supply. The grid controls the number of electrons and hence current flowing. Current flows through the primary winding of the output transformer inducing a voltage in the secondary winding which is used to drive the speaker.

3) The amplified signal travels to the rectifier which converts AC to DC...this then goes to the capacitor which apparently blocks all DC! The way I understand it is that when the rectifier changes AC to DC it isn't a 'smooth' signal...so this is what the capacitor does (removes distortion). The rectifier keeps the capacitor 'topped up' with +ve charge which is transmitted to the loudspeaker...

I'm afraid you're completely wrong here. The recitifier etc. are not in the signal path. Valves require a high voltage DC supply known as the High Tension (HT) supply of typically 150 volts. AC voltage from a tap on the motor winding is rectified to give unsmoothed DC. This has to be smoothed by capacitors to give a smooth DC. Were this not done a constant mains hum would be heard in the speaker.

Think of a smoothing capacitor as being a tank with a tap at the bottom. This will give a continuous flow of water even though the tank itself may be filled intermittently from buckets.

['LIVEWIRE?']

to 'gloves86' Rachael, you are basically correct on points 1)& 2), except that I have always understood that electron flow is from Cathode to Anode. The 'centre plate', i.e Control Grid, performs as its' name suggests. The signal from the anode(still A.C.) of the pentode* valve(The rectifier is a Diode)is coupled via the Output Transformer(top left corner item in picture) to the Loudspeaker.
What the rectifier, reservoir and smoothing capacitors do is to convert the(230v)mains A.C. supply to D.C. and filter it to provide the power supply for the signal valve. The other components include the on/off switch/Volume Control Assembly, Tone Control,plus various resistors and capacitors, whose functions are to set the correct operating conditions(DC Voltages), and to couple, decouple and filter out interference respectively. The Turntable Drive Motor is a 2 pole induction type, with a shaded pole.
A 'tap' on the motor winding is(usually)used to provide abt. 90v AC for the Valve Heaters.
* A Pentode Valve has 5 elements - Cathode, Control Grid, Screen Grid, Suppressor Grid, and Anode
I hope all the foregoing helps. More detailed information can be found, amongst many other places, on Pauls other Websites. I also have some Textbooks I would be willing to loan you. PM me if you would like to borrow them
PS I see that 'Station X' was in the process of typing a detailed and very good explanation as I was writing mine.

[Stewart]

Just to add a little further information about this unit - it uses the TU12 turntable (unit) and the model PU30 tone arm (pick up). As has been stated these were made by BSR Ltd and bought in by many manufacturers of the day for fitting into there own equipment.

[Welsh Anorak]

Hi
Just a small point. It looks as if the machine has been upgraded at some point (the blue capacitors). However, the mains cable looks like it's not polarised - is that correct? If so there's a 50/50 chance the metal chassis could be live - that's not a nice thing to happen - and definitely not the way to learn about electron flow!!
Glyn

[gloves86]

Yeah I'm pretty sure you're right about the live chassis Glyn...I've had a very nasty shock off it a few times! Another reason I stopped using it!

The information is top notch, thanks everyone...I understand how it works now!

@Stewart: would it be possible to get those two pictures complete? One side of each pic is cut off...they would really help with my project as I would know exactly what 'bits' went into the turntable and tone arm to make them up! I would really appreciate it!

[Stewart]

Rachael - I've undone the binding on my BSR manual so I could fit the full pages on the scanner. If you send me an e-mail address by private message (see top right of page) I'll forward on the scans to you at a good resolution. There is also a parts list page and one for the motor assembly too. I wondered if they might be of interest!

[Herald1360]

FWIW I've just noticed that the photo shows the pole shading on the induction motor clearly. It's the two copper loops around part of the lamination stack.

[Tom_I]

A similar motor shown here.

[gloves86]

Ah excellent thank you! Stewart - you have a PM

[Tom_I]

I've just been browsing over at the excellent Nederlands Grammofoon Genootschap site, and came across this page about the Perdio C104 which looks a lot like this Westminster record player. It's not identical, and in particular the component layout shown is a bit different, though I suppose there could have been variations during production.

Perdio certainly made radios for Currys to sell under their Westminster brand name. Maybe they also made this record player?

Just a thought.

Tom

[gloves86]

Hmm...interesting find tom! thanks very much for that does definitely look similar...I think you might be right in that they made it for Currys!