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Author Topic: Noisy Ham III Rotor Brake relay!  (Read 1045 times)
N9MXY
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Posts: 237




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« on: March 09, 2012, 05:02:58 PM »

I have a Mid 70's Steel case CDE HAM rotor controler and for some reason the brake release relay hums and vibrates when engaged, applying rotation to the rotor drops it a little but it's loud enough to force me to turn up the volume on my reciever to copy a QSO while using the rotor.  There is a little PCB mounted on the underside of the controler behind the three paddles that the Brake relay is mounted.  It has a couple small Caps, 4 diodes a couple reistors and a 2n3904 Transistor. I wonder if this is an after market brake delay or if this is OEM and what the problem may be.  It looks like it's just a SPST relay but I've never seen a relay go bad in such a way so I'm not keen on hunting down one and swapping it out.

Anybody else run acros this problem?

73 carl
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KM3F
Member

Posts: 499




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« Reply #1 on: March 09, 2012, 08:32:34 PM »

Sounds like your describing a brake delay release timed relay board.
They are usually addons.
Get in there and trouble shoot the circuit.
A shorted diode will apply AC to the relay such that it may vibrate at the power line 60 hertz rate.
When the left or right paddle is operated with the brake release, the brake stays operated for about 30 seconds after you release all paddles to give the rotor time to come to a stop before the brake locks up the ring gear in the rotor.
All the circuit does is rectify some AC from the transformer that charges up a capacitor.
The voltage and capacitor charge holds the relay operated until the relay winding discharges the capacitor below the drop out voltage of the relay after center paddle release, then the relay drops allowing the rotor brake to drop the lock against the rotor ring.
I don't think it's a bad relay.
Good luck.
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N9MXY
Member

Posts: 237




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« Reply #2 on: March 10, 2012, 04:49:17 AM »

Yeah, I was just looking for an easy way out. Smiley  Found 3 bad rectifier diodes which gave my 7yr old a chance to wield the solder sucker and cut the excess tails off the new diodes once soldered in place.  I found out that if I remove the ground to the board the rotor still works 100% and makes no noise at all so in the worst case I'll just leave it unhooked.  After the 3 diodes I still have hum but it is somewhat muted. I also have no brake release delay yet nor any voltage to the LED above the paddle.  There is also a small signal diode on the board that is bad. I'm going googlling to see if I can find a schematic for the board. If not I'll just try a good ol 1N34, 37 or some such generic signal diode..
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