An old friend has just donated a couple of analogue synths - a Yamaha CS-5 and a Moog Prodigy. The Yamaha is in perfect working order, albeit a bit tatty. However, I noticed that the little red speed LED on the far left of the unit had stopped functioning.

I found a nice green replacement one from an old PCI Network card and proceeded to oik out the old one. However, in the process I managed to destroy the black grommet that holds it in place. Is there anywhere I can get another one of these or at least something that does the job? Also, do I need to consider the voltage etc., or are they all standard?

Also, I haven't checked out the state of the Moog yet as it has no mains lead. So, is there an obvious starting point for sourcing a new power lead (or supply)? It's a round, three-pin jobbie.

These are my first ever analogue synths so forgive my ignorance on the subject.

Many thanks in advance.

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First of all, may I congratulate you on being a very lucky individual indeed (decency prevents me expressing my real feelings )!
It it's just a standard LED grommet you can pick them up for pennies at any Maplin store.

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Also, do I need to consider the voltage etc., or are they all standard?

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The brightness of LEDs is dependent on current, not voltage (the voltage drop across them is essentially fixed), so you just need a suitable series resistor between the output of the oscillator and the LED to provide a current of a few milliamps through it.

The chances are that the existing one will be fine, and you can simply solder in the new LED in place of the old one with no other changes. However, if it's too bright then add another series resistor (off the top of my head I suspect a value between 220 ohms and 1k would do the job). If it's too dull then it's probably safer to buy another brighter LED replacement.

As for a replacement mains lead for your Prodigy, I seem to remember another recent post from someone publicising a web site offering such things for a wide range of elderly synths and samplers, so a search here should produce results.


Martin

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YewTreeMagic

Doh!

The very next thread I read was the one about mains leads. Here it is: www.soundonsound.com/forum/showflat.php?Cat=&Number=337319

and the web site is www.leadsdirect.f9.co.uk


Martin

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YewTreeMagic

Many thanks for your replies.

It's proving a good introduction to basic electronics for me, although the range of LEDs on offer at Maplin is a little daunting - so bleedin' many of them.

Cheers.

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(..)the range of LEDs on offer at Maplin is a little daunting - so bleedin' many of them.

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I suspect a standard diffuse (or clear-type, depending on your personal preference) LED with a forward voltage of around 1.8V and a current rating of between 5 and 20mA will do.

Green and yellow LEDs usually require a slightly higher forward voltage (slightly over 2V), if you'd replace a standard red LED with a green one, chances are that the green LED will be slightly dimmer in comparison.

Cheers,
Frank

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Imagination is more important than knowledge - A. Einstein