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Author Topic: Alpha Delta coax switch - bad position?  (Read 6697 times)
ND6P
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Posts: 96




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« on: December 07, 2012, 05:25:14 AM »

Yesterday, I was surprised to find out that my 5-band hexbeam had stopped working.  I traced the problem to a bad position on my Alpha Delta 4 position coax switch.  I moved the hexbeam to another position on the switch to get back in business.

Has anyone else had one of these switches do this?  I bought mine new a few years ago.  The switch motion feels fine and the arc plug is okay.  Continuity is infinite on the bad position, the most counterclockwise on the switch.

Are these repairable?

Thanks,

Jim/ND6P
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KE3WD
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Posts: 5689




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« Reply #1 on: December 07, 2012, 09:34:09 AM »

Take it apart and investigate. 

73
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WB2WIK
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Posts: 20612




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« Reply #2 on: December 07, 2012, 02:21:30 PM »

They are reparable, and I think what happened to yours is quite unusual.

I have three of the 4-position A-D switches in service since 2001 and used every day and none have ever failed in any way.

Make sure the pin contacts in the SO-239 connector haven't spread out and aren't actually the cause.
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K8AXW
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Posts: 3900




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« Reply #3 on: December 07, 2012, 09:21:16 PM »

I agree with 3WD.  Alpha Delta is good stuff and repairable.  Take the rear plate off and look at it. 
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ND6P
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Posts: 96




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« Reply #4 on: December 08, 2012, 12:37:30 PM »

Well, I just tried to take it apart to have a look. 

There is a third screw on the bottom under the label that says 'do not open, no serviceable parts inside', that is actually not a screw at all: it's a rivet to make the switch tamper resistant.  Rather than put my good three-position switch at risk, I stopped right there and put the switch back into the system.

I did notice brief continuity at the bad position while I was fooling with it on bench, but after operating the knob, the continuity never returned. If and when I add another antenna, I will need to get a new switch, or maybe go to a patch panel.
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K8AXW
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« Reply #5 on: December 08, 2012, 09:25:12 PM »

Contact Alpha Delta and explain the problem.  I'm quite sure they'll tell you what is wrong and how to open the switch.  If they refuse, then I suggest you indicate that you'll be replacing it with another brand.
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KE3WD
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« Reply #6 on: December 09, 2012, 08:08:28 AM »

Well, I just tried to take it apart to have a look. 

There is a third screw on the bottom under the label that says 'do not open, no serviceable parts inside', that is actually not a screw at all: it's a rivet to make the switch tamper resistant.  Rather than put my good three-position switch at risk, I stopped right there and put the switch back into the system.

I did notice brief continuity at the bad position while I was fooling with it on bench, but after operating the knob, the continuity never returned. If and when I add another antenna, I will need to get a new switch, or maybe go to a patch panel.

In my shack, if the warranty is expired, a label like that represents a challenge. 

Out comes the electric drill and small bit of the right size to drill me out some rivet...

But your discretion-is-the-better-part-of-valor is also well understood. 


73
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ND6P
Member

Posts: 96




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« Reply #7 on: December 10, 2012, 04:24:40 AM »

Well, I just tried to take it apart to have a look. 

There is a third screw on the bottom under the label that says 'do not open, no serviceable parts inside', that is actually not a screw at all: it's a rivet to make the switch tamper resistant.  Rather than put my good three-position switch at risk, I stopped right there and put the switch back into the system.

I did notice brief continuity at the bad position while I was fooling with it on bench, but after operating the knob, the continuity never returned. If and when I add another antenna, I will need to get a new switch, or maybe go to a patch panel.

In my shack, if the warranty is expired, a label like that represents a challenge. 

Out comes the electric drill and small bit of the right size to drill me out some rivet...

But your discretion-is-the-better-part-of-valor is also well understood. 


73

I'm the same, but in this case the rivet was solid and was aligned with the switch shaft.  I was concerned that I could have messed up the switch mechanism if the rivet end was an integral part of it. If another position fails, I'll definitely open it up to see what is going on.

-Jim

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K5LXP
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Posts: 4507


WWW

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« Reply #8 on: December 10, 2012, 06:39:10 AM »

If another position fails, I'll definitely open it up to see what is going on.

What I would be doing is sourcing its replacement before it failed again.  Once the replacement comes in you can do a post-mortem on it.  If you end up being able to repair it, it becomes a spare.  If it's BER, pitch it and you're done.


Mark K5LXP
Albuquerque, NM


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KE3WD
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Posts: 5689




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« Reply #9 on: December 10, 2012, 09:49:27 AM »

It is only sound thinking to obtain a replacement beforehand, if the need to operate is an issue. 

For a contester, that would be a no-brainer. 

But I'm like this about such things, if one good man designed and built it, then another good man can figure it out. 

Of course, I'm rather proud of the times I've made the smoke come out. 

You haven't lived until you've bricked something worth millions on the job...

73
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K8AXW
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Posts: 3900




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« Reply #10 on: December 11, 2012, 11:00:55 AM »

3WD:  You have that right!  After operating a 150 million dollar black liquor recovery boiler that can go from 200ft high to a hole in the ground in a few seconds, tearing a coax switch apart is somewhat ho-hum!   Smiley

My philosophy is similar to yours.  I figure if a man built it another man can take it apart!
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AA4HA
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Posts: 1492




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« Reply #11 on: December 11, 2012, 07:29:38 PM »

My philosophy is similar to yours.  I figure if a man built it another man can take it apart!

A man takes it apart, a woman fixes it.  Wink
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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
K8AXW
Member

Posts: 3900




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« Reply #12 on: December 11, 2012, 08:38:28 PM »

OUCH!  Nice shot Tisha...... someone help me pull this out.......
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KE3WD
Member

Posts: 5689




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« Reply #13 on: December 12, 2012, 12:17:49 PM »

Well, this man REPAIRS it.

See, my first wife had the cat fixed. 

And forever thereafter, he was different.


73
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WB4ILP
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Posts: 38




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« Reply #14 on: December 13, 2012, 09:46:28 AM »

Hi Jim !
When I first came to Alpha Delta one of my jobs was repairing switches.  I'm very familiar with this rare type of failure.  It is caused by a slight bending of the "common contact" raising the semi-circular contact at one end or the other.  In your case the contact is a little high on the position 4 end.  The contact is made from silver plated phosphor bronze and it very rarely can move a little due to heating by RF currents or a lightning surge.  It is a very simple fix.   You should be able to remove the back cover.  All fasteners should be screws as we don't use rivets to secure the back plate.   The "common" microstrip contact is soldered to the center pin of the "common" connector and it extends into the switch cavity where it becomes a semi-circular contact for all 4 positions.  All you need to do is tweak it just a little to slightly lower the end of the semi-circular contact over the position 4 contact.  Not too much, we are talking about maybe 1/16 inch or so.  You can put the backplate on and hold it together like a sandwich to check your work.  It may take a couple of tries to get it just right. Also make sure that all the other positions are still working.  Button it up and you're back in action.  If you have difficulties please call me at (888) 302-8777 and I'll arrange a free repair.
Thanks Jim and good luck with the repair.
Jim, WB4ILP
General Manager
Alpha Delta Comm.
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