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Author Topic: Collins S3 Line question - HELP  (Read 917 times)
W4PBU
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Posts: 86




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« on: September 16, 2009, 09:02:41 AM »

Hello boys & girls
After drooling over the Collins gear for over 50 yrs my S3 station finally arrived last week but I have not been able to make the first contact as I have problem.
I have the xmtr, rcvr, station console & power supply all cabled properly with Collins cables.
Not using any vox or phone patch cables.
Xmtr loads up properly, rcvr works fine.
I have everything set up for transceiver operation with ptt, no vox.
When I key the mic the rcvr mutes as I think it should but when I release the ptt button on the mic the receiver does not come out of mute condition.
I have to turn off the xmtr to restore audio to the rcvr and if I key the mic again the same thing happens.
I have a feeling that the relay in the xmtr is not releasing until I turn off the power, energizing with ptt but not releasing.
The same situation in both rcvr vfo and xmtr vfo modes.
I need help.
Any suggestions would be greatly appreciated.
Thanks
Dave
W4PBU
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WD8AJY
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« Reply #1 on: September 16, 2009, 09:17:03 AM »

Check R140 and R88 on pin 8 of V11 A I had the same problem with my KWM-2A and the cathode resistor was open. Good luck (Bob WD8AJY)
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W0BTU
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« Reply #2 on: September 25, 2009, 09:18:47 AM »

I agree with the other replies, and the vox control misadjustment is probably the problem.

However, I had exactly the same problem as you described in your first post, and it was simply the receiver mute contacts on one of the relays in the transmitter.

I have had to clean the relay contacts several times over the years, until one time cleaning (using a small strip of crocus cloth held with a hemostat) didn't help -- the contact was worn. After carefully bending the contact, I haven't had a problem since.

What did you find?

73 Mike
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W0BTU
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« Reply #3 on: September 16, 2009, 04:10:55 PM »

Another thing to check is the mute contacts on one of the relays. I have had to clean the mute contacts several times over the years, until one time cleaning didn't help. After carefully bending the contact, I haven't had a problem since.

73 Mike
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W0BTU
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« Reply #4 on: September 16, 2009, 04:12:23 PM »

And you should only use crocus cloth to clean the relay contacts.

73 Mike
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W4PBU
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Posts: 86




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« Reply #5 on: September 16, 2009, 08:48:49 PM »

Thanks for the suggestions on the relay, However, the relay is working just fine, the problem is that it will not de-energize after I release the ptt bar on the mic, only if I turn the xmtr off and then back on again.
Come on guys, please, someone must know what is going on here.
All suggestions will be appreciated and cked.
Thanks
Dave
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G3RZP
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« Reply #6 on: September 17, 2009, 01:23:05 AM »

If a relay won't release, it's usually due to residual magnetism. Put a piece of thin paper between the relay armature (the bit that moves) and the core of the coil. If that clears it, residual magnetism is the problem. In that case, a layer of Scotch tape over the armature will usually last for quite a time. If you can't get at the armature because it is a sealed relay, you have to bite the bullet and change the relay.
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WD8AJY
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« Reply #7 on: September 17, 2009, 05:37:57 AM »

Check the voltage on pin 8 of V11A it should be about +5.5 volts if it is low the tube will conduct more incressing the current through the relay. when you key the transmitter the relay will pullin when you unkey it there will still be enough current on the relay to keep it energized. If R140s resistance is to high this will cause the problem.

Bob WD8AJY
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W4PBU
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Posts: 86




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« Reply #8 on: September 17, 2009, 05:01:03 PM »

Bob;
Thank you very much for your help.
I have spent 2 full days trying to track this problem down.
After not finding anything above the chasis I decided to follow you suggestions and ck the resistance of R140 & R88 and the voltage at pin 8 of V11.
R188 should be 1500 ohms and that is what it measures.
R140 should be 34k and this is what I found.
  Someone before me has apparently had the same
  problem as they have installed two 57k resistors in
  parallel. Should be 38.5k and that is exactly what
  it measures, Houwever, you and the schematic say
  it  should  be 34k = 4.5k too high although within
  12%.
  Incidently the resistors get quite hot although no
  sign of burning.
The votage at pin 8 of V11(6AU8) is 13.3 volts until I close the vox/ptt switch, which is what the manual calls for, then it drops to 5.7 volts.
When I open the vox/ptt switch the voltage increases  to 12.15 volts until a few seconds later the relay opens and then the voltage is back to 13.3 volts.
I hope that some of this will help you further diagnose the problem.
One gentlman suggested placing some tape between the relay coil and the plate to eliminate residual magnetism, what do you think.
Again, any and all help is greatly appreciated.
Thanks
Dave
W4PBU
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WB6BYU
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« Reply #9 on: September 17, 2009, 05:15:57 PM »

W4PBU wrote;
>  One gentlman suggested placing some tape between the relay coil and the plate to eliminate residual magnetism, what do you think.

I think I would value that particular gentleman's advice
rather highly.

This fix doesn't eliminate the residual magnetism, but
rather reduces its effect, hopefully to the point where
it no longer holds the relay in too long.

If you measure the voltage across the relay coil and the
relay doesn't open when the voltage drops out, there are
three likely conditions that will cause it:
(1) there is still enough voltage across the relay to energize the coil;
(2) there is a mechanical defect in the coil (like sticky
contacts) that prevents it from opening; or
(3) the residual magnetism in the core is sufficient to
hold the relay in even with no current flowing.

You can test this by disconnecting one of the relay
terminals (or perhaps unplugging the tube that drives
it so there is absolutely no current through the coil.
If it still doesn't open, suspect the residual magnetism.
(Or it may be a combination of the residual magnetism
PLUS some residual current being just enough to hold the
relay in, in which case removing the current would still
open the relay.)

The addition of tape or paper increases the spacing between
the relay armature and the magnet pole.  The idea is
that the pull of the residual magnetism will decrease
with distance, and this will be enough to allow the relay
to release when the coil is no longer driven.  It takes
little time or expense to try, and the worst that can
happen is that you've lost a couple extra minutes after
two days spent already.
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W5HTW
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« Reply #10 on: September 17, 2009, 05:40:56 PM »

Hate to say it, but I think it is simpler than what you have been told.

I think you'll find the problem in the adjustments of the anti-vox and vox sensitive controls.  Even using PTT, the anti-vox will hold the receiver muted if it is not adjusted properly, and that adjustment can be extremely critical.  

I would suggest you back off ALL the vox controls to minimum.  Then increase the vox sensitivity until it just barely trips with a loud noise in the microphone.  Or, if using CW, until it just begins to trip reliably when pressing the key.  

At that point, the receiver may return immediately to receive operation when you release the PTT switch.  

The next step is to adjust the vox delay.  Adjust it for a comfortable time delay.  

Only when you have that done, should you start to adjust the anti-vox.  And those adjustments will be very, very small!  

I adjusted the anti vox until the vox circuit would no longer kick in with loud speech.  Then I backed it off slightly.  

Balancing the effects of those three controls can be very difficult and time consuming.  

If you are ONLY using PTT, you can set the vox gain at zero, but you still need to adjust the vox delay and the anti vox!  

I had a LOT of trouble getting my S-line to work and it was all in the adjustment of the three vox controls.

And yeah, even using PTT the anti-vox and the vox delay are both still active and have an effect.

Good luck.  If it is not in the settings of these three controls, then you will need to do some in-depth trouble shooting.  

Remember!  All vox controls to minimum!  Check the rig that way.  If the mute works, you know it is in the control settings.  From there on out, it is simply a matter of making tiny adjustments.  

Once set, they will hold for a very long time.  You may not have to ever reset them.  But getting them right the first time may take a lot of patience!

Ed
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W4PBU
Member

Posts: 86




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« Reply #11 on: September 17, 2009, 06:59:16 PM »

Thanks again for the replies.
Ed, the ham that I bought the equip from told me today that the three vox controls needed to be adjusted but did not give me any directions as you have done, thank you.
I will be trying that tonight.
Do I have to have the "ant-vox" jacks on the rcvr & xmtr cabled together as I had not done that since I was not planning to use vox?
I will let everyone know when and how this gets solved.
73
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W5HTW
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« Reply #12 on: September 18, 2009, 07:04:58 PM »

Yes, you need them cabled together.  If you are not going to use VOX, simply set the VOX gain at minimum and use PTT.  But the VOX delay will still be effective, as will the anti-vox.  

Good luck

Ed
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