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View Full Version : WTB: KW Cross Needle SWR Meter



W3WN
12-18-2011, 08:58 PM
One of my Daiwa CN-101L SWR Meters failed last night. Will only read a 2:1 SWR on low power setting, no forward power on medium power.

So I need a replacement. (Of course, I'm also hunting down a schematic to see if I can fix it! Whether or not I can, or have time to, remains to be seen)

I'm looking for another one. A CN-101L, an older CN-620B, or something similar. Dual/Cross needle, and capable of handling 1 KW so I can hook by AL-84 to this rig.

If you have one, please PM me and let's see if we can work something out.

Thanks!

K6BSO
12-18-2011, 09:03 PM
Ron, I have a CN-620 that works, but the needles on the meter were damaged by poor packing when it was shipped to me. If the meter movement on yours is still good, perhaps you'd be able to swap them? If you're interested, it's yours for the price of shipping and handling.

N8YX
12-19-2011, 08:08 AM
Open your meter up, identify and replace the diodes which are in the line sampler portion of the circuit. One or both has failed.

W3WN
12-19-2011, 08:38 AM
Open your meter up, identify and replace the diodes which are in the line sampler portion of the circuit. One or both has failed.Thanks Fred. I'll do so the first chance I have, but between last minute shopping and family this week, it won't be until next week at the earliest.

N8YX
12-19-2011, 09:45 AM
Thanks Fred. I'll do so the first chance I have, but between last minute shopping and family this week, it won't be until next week at the earliest.

My guess is they're germanium - 1N34, 1N60, etc.

Surplus Sales has these for a quarter apiece:

http://www.surplussales.com/Semiconductors/Germanium.html

If the diodes in the meter have a larger, clear glass body then the ones above will work. I doubt Daiwa uses silicon diodes (1N914, 1N4148, etc) in the detector but stranger things have happened.

Let me see if I can find a schematic online for the unit and I'll verify this.

K7SGJ
12-19-2011, 09:52 AM
I think you're right Fred, and Ron if you need some, I've got a row boat load of 1n60 diodes. I can toss a few in an envolpe if you need em.

N8YX
12-19-2011, 10:01 AM
Here's a typical circuit. Note the positioning of the diodes and their type - 1N914, a silicon part.

All of the metering apparati here use germanium parts in the detector, but YMMV.

5004

K7SGJ
12-19-2011, 10:34 AM
Your attachment didn't make it.

PA5COR
12-19-2011, 10:48 AM
Some series had a diode placed in the wrong direction from the factory.
http://pa0fri.home.xs4all.nl/Diversen/CN101L/CN101Leng.htm

They do indeed use Germanium diodes, i have a working one here on the shelf not used anymore.
Also the calibration practice is described following the linky.

Schottky diodes caan be used if you don't have a replacement but needs a bit allignment then.

W3WN
12-19-2011, 10:52 AM
Some series had a diode placed in the wrong direction from the factory.
http://pa0fri.home.xs4all.nl/Diversen/CN101L/CN101Leng.htm

They do indeed use Germanium diodes, i have a working one here on the shelf not used anymore.
Also the calibration practice is described following the linky.

Schottky diodes caan be used if you don't have a replacement but needs a bit allignment then.I think even I can fix that! :mrgreen: Guess I'll have to go out and buy some diodes!

N8YX
12-19-2011, 10:54 AM
Your attachment didn't make it.
Direct upload to the rescue:

5005