| Licon switch replacement [message #13322] |
Tue, 30 March 2010 20:00  |
Van
Messages: 134
Registered: April 2004
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Senior Member |
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I wonder if anyone's found a suitable replacement for this switch?
On/Off-Polarity for a K250-4.
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| Re: Licon switch replacement [message #13399 is a reply to message #13398] |
Wed, 14 April 2010 17:11  |
Van
Messages: 134
Registered: April 2004
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Senior Member |
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Cool find.
Although I see it's rated at 5 amps.
The original is rated at 10 amps. Not sure if that's overkill or not.
I found a used switch on eBay and am awaiting its arrival today (hoping).
Paid through the nose.
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| Re: Licon switch replacement [message #13462 is a reply to message #13461] |
Sat, 24 April 2010 11:24 |
fairman36
Messages: 6
Registered: April 2010
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Junior Member |
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I agree; DPDT would work for the 300/600. Also, when I had the 633-UB16KKW015CCC-RO in the K250 I was repairing, I measured 2.2 volts across the LED. While this is a bit higher than the spec rating of 1.85V and may shorten the expected life of the bulb (although I put the unit through several hours of burn-in), it is comfortably within the rating for the super-bright and should not require any extra resistors.
[Updated on: Sat, 24 April 2010 11:26] Report message to a moderator |
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| Re: Licon switch replacement [message #14521 is a reply to message #13322] |
Wed, 06 October 2010 17:21 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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The resistor is getting hot because there is a lot of current being drawn through it. There is either a short in the wiring or the led is wired in reverse, or it is shorted.
Double check your wiring and test the led.
And by the way you don't need the large 400 ohm resistors in the circuit anymore.
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| Re: Licon switch replacement [message #14522 is a reply to message #14521] |
Wed, 06 October 2010 17:46 |
dndemattia
Messages: 6
Registered: September 2010
Location: USA
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Junior Member |
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Both switches have the LED built in and are the same type discussed on this forum from Mouser. The LED in the Power switch is fine. Will check for shorts or errors in wiring on my part on the polarity switch LED (seemed pretty straight forward). What is the voltage supposed to be at the poliarity switch old pilot light? It looks like it comes right off the bridge rectifier. Just a general question - Do I really need the polarity switch? If not, how do I handle the .022 cap on the incoming AC power? Thanks again for all the help!
[Updated on: Wed, 06 October 2010 17:53] Report message to a moderator |
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| Re: Licon switch replacement [message #14525 is a reply to message #13322] |
Thu, 07 October 2010 12:02 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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The original switches had 28 volt bulbs inside of them. The 45 volts from the power supply was reduced by the large 400 ohm resistors to get to 28 volts.
If the bulb is not in the circuit, there will be no current draw and no voltage drop across the 400 ohm resistor. If you measure the voltage at the resistor, it will still read somewhere around 45 volts dc.
The LEDs will draw very little current compared to the original light bulbs. So if your dropping resistor is getting hot, there has to be a problem in the circuit.
As for the polarity switch and cap, remove the cap if you have a 3-wire power cord. For that matter you don't need to wire in the polarity switch at all.
In the old days the chassis of the amp was connected to the ac line through a capacitor, to reduce hum. The polarity switch would choose which side, either the hot or the neutral side of the ac line, would be connected to the chassis via the cap.
Modern standards do not allow for the polarity switches anymore, so some people will remove them from their amps.
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