Comet Triplexer CFX-514 Repair Notes

[Jack Crow]

Hi all,
Just finished working on a failed CFX-514.

Back Story

A triplexer is a filter device that allows different bands of radios to share a single antenna.
In this case a Ham 6M (52mhz) Ham 2M (146mhz) and a Ham 70CM (445mhz).

This radio stack was located at a friends tower site.

One day when I went to turn on the stack the 2M and the 6M units did not work well, UHF was mint.

When I jacked the antenna directly into the radios they worked just fine. Had a huge loss in the triplexer, and it is rated for a fraction of a dB.
Took it home.

Just got around to messing with it.

Checked it with a sig gen and a spec an. Had about 30dB losses in the two bad paths.

Did some DC checked and those showed shorts where there should be none.
Took out four caps and one coil and the shorts went away.
Tried to measure the caps and those showed no shorts.
Replaced them with new parts since I had them out anyway and carefully re installed the coil.

Now the unit works like a charm.

Suspect a mechanical failure rather than an electronic one. Some painted or internal area of the filter wore out and made contact with the circuit board parts. The space in the case is tight and a little bit of slop in installing the parts may have been all it needed to punch through, short, and fail.

A lesson in how not all electronics problems are caused by electronics parts but mechanical issues.

Be well all.
Jack Crow aka Radio Mike in VA

[kc8adu]

Re: Comet Triplexer CFX-514 Repair Notes

had one of those a while back that failed short due to a solder ball.killed the sav17 2m pa in the customers standard c5900.lots of lousy soldering in there.if it was branded mfj it could believe it.this happened when the rig was new and just out of warrenty.$950+ for the 5900 in 97.customer was pissed.it sat in a drawer till now.

[Jack Crow]

Re: Comet Triplexer CFX-514 Repair Notes

KD8ADU,
Now that is an expensive way to do things.
Lots of things can 'take out' an amp but this one is an irritant for sure.

I use a bunch of plexers for a lot of different tasks.

Mostly for 6 and 2M stuff.

Seems a 5/8ths antenna on 2M makes a fairly good 1/4 wave on 6m.

You may not know that I make a lot of APRS tracker radios for clients.
I take old two way radios (Midlands) and convert them up for Ham service. Then add the mods to make them work with APRS trackers.

Been working on an experiment to open up a new band for APRS, in this case 6M on 50.62mhz. This is Bob B's idea WB4APR.

At this point we have two big digi's in the area. One co located with WA4TSC/R (-6) that covers very well.
NV4FM (-6), that gets most of Fairfax County Virginia.

Back to duplexers for a moment.

On my car KA2ZEV-6 and KA2ZEV-8 I have the two trackers sharing one GPS input signal and one antenna. This works great.

Just a note, for radios I do not intend to sell I use the 'ugly' parts.
My for sale units are much nicer.
http://www.flickr.com/photos/9010884...7626491727033/

The above link will take you to a photo of the 6 and 2M radio with the shared GPS signal ribbon cable and the diplexer.

In my truck I have the shared GPS data deal but seperate radio antennas.
http://www.flickr.com/photos/9010884...7626491727033/
Look up KA2ZEV-5 and -9.

Even numbers for the car, odd numbers for the truck.

In the case of the truck's voice radios, they share one antenna. Have a
70-0375C set up for 6M and a
70-1495B set up for 2M.
Each one makes 110 watts. So a good diplexer was required.
Never had an ounce of trouble with this set up.

Use one more on the desk stack here. Using one of the tri plexers.
Have an 80 watt VHF and a 40 watt UHF radio, plus a real odd ball.

There is an experiment being run out of the other side of the state. A guy has an experimental permit to run 3kW on 70.005mhz CW. Set up an old Mid Band radio for that and all I get are spurs from various computing gadgits.

If life was easy.

Be well there.
Jack Crow aka Radio Mike
Herndon VA

[smason]

Re: Comet Triplexer CFX-514 Repair Notes

I have a Comet Diplexer kicking around somewhere. Used it to go with a dual band antenna on my Alinco 590 which has seperate VHF and UHF connectors.
I always thought they were fairly good quality. Better than anything from Mostly F__ing Junk.

You may not know that I make a lot of APRS tracker radios for clients.
I take old two way radios (Midlands) and convert them up for Ham service. Then add the mods to make them work with APRS trackers.

I just started playing around with a Tinytrak4, cool little unit.

[Jack Crow]

Re: Comet Triplexer CFX-514 Repair Notes

Sam,
If your interested I have 'articles' on how to make the most of the TT4. How to test with it to get the variables lined up to optium.

Catch me here or off list at
ka2zev@yahoo.com

Be well
Mike aka Jack Crow

[kc8adu]

Re: Comet Triplexer CFX-514 Repair Notes

even with the best stuff a dud sneaks out occasionaly.
the customer bought the rig and triplexer at r&l at the same time.the triplexer waited till just over a year to kill the pa.and it didnt just crack.i can fix cracked pa modules.it killed the final.
oh well the rig needed all the sm lytics replaced anyway.all c5900's do.and some white led's in the display so the bulbs dont cook it.now its what it should have been when new!