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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 31st Jul 2014, 2:55 pm   #1
graham1958
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Default Capacitor identfication

I am a beginner and my first project is a small 9.5V battery powered record player, a1962 Dansette Classic Transistor, but I have seen the same record deck in other similar makes of the period. It’s marked Greencoat industries Ltd, K.T.5/9/G

I am slowly identifying the components but one I not sure about. Its flat, red, roughly circular 6mm across, has two wires and is marked 2K.

It connects to the platter motor via a 1000uf 12V electrolytic capacitor.

I think it may be a mica capacitor and the 2K means 2 is a multiplier of 100 and K is tolerance of + - 10%? If I’ve got this correct what would be a modern replacement? This is my first thread and I have attached a picture.
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Old 31st Jul 2014, 3:34 pm   #2
OldBill
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Default Re: Capacitor identfication

Strangggge ! Best bet my friend is to unsolder it and put a multimeter across it on about 2kOhm resistance range. If there is NO reading then it probably is a capacitor, but would think that in that case it would be a CERAMIC capacitor. So then if it is then 2K would be the OLDER size designation, but you need to assume a VOLTAGE capability of maybe 300Volts or so so as to be on the safe side. I would not think that it would be Thermister or such more exotic device but more likely a suppressor capacitor across the motor. If it connects to the `HOT` motor connector and the other end of it to chassis ground then it likely is just a suppressor cap. ( Or connects ACROSS ) the motor. BUT IT baffles me a bit without actually seing more of the circuit.
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Old 31st Jul 2014, 3:37 pm   #3
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Default Re: Capacitor identfication

Sorry, NEED NOT BE 300 Volts if it is a Capacitor but 3x10Volt ( 30Volt ) is safe. I was thinking of a mains record player.
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Old 31st Jul 2014, 6:15 pm   #4
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Default Re: Capacitor identfication

Component pictured is a ceramic disc capacitor, not usually a change on sight part, you would be better off changing the ancient large value electrolytic capacitor in the photo.

The electrolytic capacitor is probably all but dried out and is most likely connected across the supply and may well be 'leaky' in an electrical sense which would cause voltage drop and poor performance. A new capacitor would cost very little and be considerably smaller these days.

Enjoy the hobby, people on this forum are a helpful resource.
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Old 31st Jul 2014, 8:31 pm   #5
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Default Re: Capacitor identfication

Good advice, unless you know for certain that the Ceramic is faulty, you'll do more damage than good changing it.
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Old 31st Jul 2014, 9:59 pm   #6
David G4EBT
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Default Re: Capacitor identfication

Firstly, welcome to the forum Graham.

Dansette created a bewildering array of record reproducers, both valve and transistor, with the same basic amplifiers appearing in different named reproducers (or 'record players' as they tend to be known). In the case of the 'Dansette Classic' transistor, the R&TV data states that it's basically similar to that of the 'Diplomat' and uses the same three transistor amplifier, though the Diplomat is stated as using a 9V 'PP10' (huh?) battery, whereas the Classic is said to use 6 'U2' cells (or as we now know them 'D' cells). The simple circuit only uses five capacitors - 3 x 100uF electrolytics, plus a 2,000pF (which I take to be the disc ceramic one), and a 200pF, though you do say that in your amplifier the el cap you've identified is 1,000 uF. (It's quite possible that the values vary from the R&TV data, which is very basic, and Dansette may have deviated from the original circuit too).

Even on simple equipment such as this, you do need the circuit and you need to develop the ability to be able to identify components and their role by referring to the circuit and comparing it to the layout. This is especially so when there is only a circuit diagram and no diagrams to identify the components, as is so in this instance. A good approach to my mind if you intend to change components is to first check them, rather than to assume they all need changing simply on the grounds of age. I say that because if you start unsoldering components - especially on older printed circuit boards where the board is SRBP (borwn stuff) rather than fibreglass, the copper tracks adhere very poorly and a lot of skill is called for. For example, never simply apply a soldering iron to a PCB pad with the old component still in place because if you do, the component will act as a heat sink and by the time you've melted the solder, the PCB track will have lifted. Instead, snip off the component leaving maybe 6mm of wire still in place, then grip the wire from above the circuit board with locking forceps melt the solder beneath the board and gently pull the wire out of the hole. Don't use a solder sucker on older boards - if you need to clean out the hole, do it with a darning needle.

In equipment that's already working, albeit not perfectly, it's always best the test it after each component change because of you change ten components, then switch on and it doesn't work, you've got quite a task on your hands to find out why. Really, what I'm saying is to try to develop a methodical approach by testing components in situ where possible and if the measure OK, leave well alone. For example, the amplifier uses 11 resistors, only one of which is close tolerance (or what in the early 60s passed for close tolerance), +/- 5%. Most of the resistors will probably have drifted high over the years, but if they're say plus 25% or even higher, just leave them alone.

To check electrolytic capacitors you can buy a cheap tester of the type that abound on e-bay for about a tenner and have been much discussed on this forum and are quite good enough for hobbyists. They test resistors, transistors, diodes, inductors and capacitors. In the case of electrolytics, they also check the Effective Series Resistance (ESR). Personally, in this instance, I'd check the ESR and capacitance of the three electrolytics and unless they showed up as untoward, I'd leave them, but if you want to replace them simply on age grounds, and can do so without risking damage, they only cost a few pence each. (It's highly unlikely that either of the disc ceramic caps will be duff).

When you say 'its connected via a 1,000 uF capacitor to the motor', I think if you study the circuit you'll most likely find that one side of the motor, and one side of the capacitor (the + side) along with several other components including the pick-up and one end of the primary of the input transformer, are all connected to the common ground, which as I say, is positive - not negative, as the amplifiers uses PNP transistors.

It's a nice little project to start off with as it's battery - not mains, so there are no safety concerns, but really in my view it's essential to get a copy of the circuit, which you can get for £1.99 at the top RH of the screen. (In fact you'll find that the data includes other Dansette amplifiers). The 2,000 pF cap is C3 on the circuit, one end of which goes to R4 - a 22k resistor, the other end, as I say, goes to the common ground, as do several other components.

Not much of what I've written will make a lot of sense without reference to the circuit, but I hope it helps a little, albeit it goes way beyond answering your question re 'capacitor identification'!

Best of luck with the Dansette.
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Old 1st Aug 2014, 10:07 am   #7
graham1958
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Default Re: Capacitor identfication

Thanks to everybody for your great advice. I have downloaded a copy of the circuit diagram. I am approaching this project slowly, the record player isn’t working but I am using this more to educate myself and the fact I can’t kill myself with 9V.
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Old 1st Aug 2014, 11:47 am   #8
David G4EBT
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Default Re: Capacitor identfication

When you say 'it isn't working' Graham, do you mean that nothing is working - not even the turntable, or do you mean the turntable revolves but no sound comes out of the speaker? If nothing is working, I'd suspect the battery connections and double pole switch being open circuit, because if no sound, you should still have 9V to the motor connections.

If the motor turns but you get no sound, by far the quickest and easiest way to identify the fault is by using a simple signal injector.

You can check out the transformers of course with a multi-meter on the Ohms range to make sure the various windings aren't open circuit, but with a signal injector you can start at the speaker, then inject a signal at various points to see if you get sound out of the speaker. So for example, if you hear a tone when you inject a signal at the base of TR3 and TR2, and at the collector of TR1, but hear nothing when injected at the base of TR1, that points to TR1 being defective. However, if you hear a tone at the base of TR1, and also at the slider of the tone control and volume control, but no sound if you scratch the stylus gently with your finger, that points to a duff stylus or it's connections.

Not exhaustive, but it gives you an idea, and it's much better than making assumptions based on guesswork, that for example maybe the transistors are dud, or maybe you should change the electrolytics. As I said in my earlier post, with one of those little Chinese Multi-testers you can test all of the components in your Dansette, and together with a simple signal injector should soon be able to pinpoint the fault(s).

As you check various parts of the circuit, it's a good idea to use a highlighter pen to go over the circuit to remind you which bits you've tested so you don't lose track.

There's a link to a forum thread below about various simple signal injector designs. A little time spent building an injector will soon repay you in time save on fault tracing. If you don't fancy a homebrew design, can highly recommend the Velleman K7000 kit from ESR Electronics, which will set you back about a tenner. All you need to complete it is a small speaker a project box and test leads etc:

http://vintage-radio.net/forum/showthread.php?t=84540

You're wise to start with a simple transistorised design rather than a live chassis radio.

Have fun!
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