SC600 Meter Bulb Replacement W/LED

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SC600 Meter Bulb Replacement W/LED

Postby Derrick » Thu Jan 28, 2016 9:09 pm

There are a few posts about this, but confusion specific for the SC600 and the like.

There are two meters movements installed on a circuit board.
Each meter movement has 1 bulb in them and both meters/bulbs are wired in series with a 100 ohm resistor between the two movements. I measure 24VDC feeding the two meter movement bulbs. See attachment to see a crude drawing of what it looks like.


It was suggested in another thread that you just replace the 100 ohm resistor on the board with a 1K resistor and the bulbs with an LED or two...

Question: doesn't the voltage drop resistor have to be connected to the positive lead on an LED, or in this case, the positive of one LED feeding the next LED in series? That would mean I couldn't put it in the position of the 100 ohm already on the board between the two meter bulbs because it would be on the positive of one LED and the negative of the other?
Attachments
600 meter board.jpg
SC600 meter circuit
Derrick
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Re: SC600 Meter Bulb Replacement W/LED

Postby Jim Williams » Fri Jan 29, 2016 11:04 am

I use a 1k 1/2 watt resistor in series with a 1N4002 rectifier diode to supply a polarized DC feed. Then soft white LED's are used. They are sanded to difuse the light.
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Re: SC600 Meter Bulb Replacement W/LED

Postby Derrick » Fri Jan 29, 2016 12:11 pm

Hi Jim, thanks for your response. I gathered this information from previous posts, however, my question is regarding the actual wiring/parts arrangement for the 600 per my crude attached drawing. It was suggested that one would simply replace the bulbs with the LED and replace the 100 ohm resistor on the board with the a 1K resistor (and in your suggestion here a diode as well). I am asking if this would work since it is my understanding that the load resistor has to be on the positive leg of the LED and any subsequent LEDs would have to be tied to the negative of the fist LED to receive the protection of the 1k load resistor. Is that the case or can I just put an LED in place of each of the two bulbs and replace the 100 ohm with 1K and a diode? I refer to my drawing above for the stock layout. Thanks!
Derrick
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Re: SC600 Meter Bulb Replacement W/LED

Postby Derrick » Sat Jan 30, 2016 10:37 am

Hmm... it doesn't look like my circuit layout drawing came through above, so I did a better one and here it is... the drawing below shows the stock layout from the factory:

Image


Below is a drawing of what other threads have suggested I modify the above stock layout to... does this seem wrong?:

Image
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