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Author Topic: Kenwood SW-2000 SWR/Wattmeter Lamps  (Read 5422 times)
WA2OLZ
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Posts: 64




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« on: January 30, 2013, 12:42:18 PM »

The Kenwood SW-2000 SWR/Wattmeter is one of the hidden gems in Hamdom. You know how good they are if you are fortunate enough to own or have used one. This, however, is not a review of the meter; there are plenty of those available available through the search button.

There is one annoying 'feature' of the meter especially obvious to those of us with aging eyes: the blankety-blank meter lighting is appropriate for a romantic dinner with mood lighting, but hardly up to the task of making the scale and needle visible. I have observed this candle lit appearance on five of the five meters I have used so assume it is universal. There are articles available pertaining to performing surgery on the meter to replace burned out bulbs (or maybe replace with a mini-LED). It appears the process is doable, although delicate. BUT - why is the lighting so poor in the first place?

Kenwood's schematic shows two lamps in parallel fed by the DC supply. I can only assume, therefore, these are 12VDC pea lamps and not up to the task at hand. Has anyone replaced the lamps with similar sized 6VDC lamps. If so, was it worth the effort? It sounds like a simple experiment, and maybe it is for younger folks with a steady hand and eagle-like vision. I'd much prefer to perform that particular brain surgery one time since I don't fall into the young category!

Tnx & 73
Jack
WA2OLZ

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KE3WD
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Posts: 5689




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« Reply #1 on: January 30, 2013, 02:13:03 PM »

Try replacing with 8V lamps. 

They will run brighter with 12V supply, but will run less hot and likely run longer than trying to use 6V lights driven by 12V.  And you won't have to rewire.


73
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K8AXW
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Posts: 3900




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« Reply #2 on: January 30, 2013, 08:24:36 PM »

I know what you are saying.  The older I get the dimmer those little lights become..... and people don't talk as loud as they did a few years ago! 

So.... the answer is to replace these inadequate bulbs with white LEDs.....once!

Since your present bulbs are supplied with a DC voltage then it would be a simple matter of dropping the voltage with a resistor or resistors.  The process might be trying but you'll have to do it only once.

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KA1MDA
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Posts: 543




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« Reply #3 on: January 31, 2013, 10:16:49 AM »

Try replacing with 8V lamps. 

They will run brighter with 12V supply, but will run less hot and likely run longer than trying to use 6V lights driven by 12V.  And you won't have to rewire.


73

Be careful installing lower voltage lamps, as I have seen situations where the result was melted plastic due to the additional heat generated by the lower voltage lamps. LED's would be the way to go.
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KE3WD
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Posts: 5689




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« Reply #4 on: January 31, 2013, 02:02:31 PM »

Good point, I warned the same guy about that in his same post over on QRZ, but neglected to mention the heat issue here. 

On the other hand, LED conversion, no heat to speak of...


73
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K8AXW
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Posts: 3900




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« Reply #5 on: February 01, 2013, 09:46:53 AM »

I found this product at Allelectronics.com.  I found it so great that I'm incorporating it in my homebrew projects as well as my 'store-boughten' gear as it becomes necessary. 

The 3-LED strips come with its own dropping resistor which means you can run it from 13.8VDC without calculating and installing an external resistor.  What's more the back of the strip has an adhesive which can simplify mounting.

To quote Allelectronics:

Bright, flexible, easy-to-use LED light strip. Ultra-bright, white surface-mount leds on a flexible, 8mm wide, adhesive backed ribbon. Ideal for accent lighting in auto or home. Also great for under cabinet or shelf lighting. Ribbon strip can be cut every 50mm (approx. 2"). Each 50mm segment consists of three LEDs on 15mm centers and can be lit independently. Each segment has clearly marked solder spots for power connection. Wires can be soldered directly to ribbon tape or, push-on connectors, CAT# CON-121 and CON-122 are available. Sold as a continuous ribbon, up to 5 Meters (100 segments). Priced per 3-led, 50mm segments.

We also have this in "Warm-White," CAT# LS-12-WW and "Neutral-White," CAT# LS-12-NW. "Cool-White" is whiter, more like a fluorescent light. "Warm-White" is yellower, more like an incandescent light, and "Neutral-White" is somewhere in between.

Specifications:
12Vdc, 25 mA per 3-led segment
Color temperature: 6500K
Viewing Angle: 120 Degree
Peel-off 3M® adhesive backing


I use the LS-12-NW and vary the brightness with a dropping resistor or pot if I find it necessary.  Most of the time I use a 3-LED strip as is.  I use a 6-LED strip under a homebrew 'hood' to illuminate an LCD screen which I can now see from several feet away.
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