Servo amp issues

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rockdrummer

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Servo amp issues
« on: 8 Dec 2018, 02:06 pm »
Hey everyone.
About 4 years ago I built my brother a sealed sub and xls encores. His servo amp is not outputting sound like it should. It makes a very faint sound but only when it is turned up pretty loud. We took out the driver and checked the connections and wiring to the best of our ability, and I can't find anything obvious.

Is this anything anyone has solved themselves or do I contact Rhythmik for a possible repair?
Thanks
Ben

HAL

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Re: Servo amp issues
« Reply #1 on: 8 Dec 2018, 02:13 pm »
A couple of things to try to isolate the problem.

Have you tried a different source and cable to the servo sub amp to see if there is any change?

Did you check the resistances of the driver and servo coils on the speaker? 


ASCTLC

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Re: Servo amp issues
« Reply #2 on: 8 Dec 2018, 03:26 pm »
Check for a speaker output fuse.  I'm not familiar with that servo amp but on the amps and receivers I've had (so far) they have all had a speaker output fuse per channel and when they blow it results with a very low (and somewhat distorted) output.

Danny Richie

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Re: Servo amp issues
« Reply #3 on: 8 Dec 2018, 04:00 pm »
Try what HAL suggested. If the problem remains then we can contact Brian at Rythmik. He will likely ask you to send it to him to get it checked out.

Hirst

Re: Servo amp issues
« Reply #4 on: 8 Dec 2018, 06:49 pm »
Check to see if the cables are plugged into the correct jack.......don't ask me how I know  :duh:

Paul

rockdrummer

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Re: Servo amp issues
« Reply #5 on: 9 Dec 2018, 03:05 pm »
Thanks for the help everyone.

We did try a different source and receiver, but we didn't have other cables to test with. I will make the trip over there with cables and a multimeter. I don't know how to test the actual speaker coils, or at least I wouldn't know what the resistances should be. Must be simple but I have never done it.
Thanks
Ben

HAL

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Re: Servo amp issues
« Reply #6 on: 9 Dec 2018, 03:16 pm »
Ben,
Just remove one wire from the Servo coil terminals and with an ohm meter set to a low range (like 200 ohms) and measure the resistance.  Make sure the amp wire does not touch the speaker terminal while you are measuring.  Write it down with the Servo coil name.  Then connect the wire back to the terminal.   

Do the exact same thing for the Drive coil terminal resistance measurement. 

Post the two resistance measurements with the coil names and which style servo sub speaker you have in the thread. 

rockdrummer

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Re: Servo amp issues
« Reply #7 on: 9 Dec 2018, 03:25 pm »
Thanks Hal, this is going to be a silly question, but do you mean with music playing or without?

Do I remove either + or - ?
I'm a total rookie who can follow directions, but I know very little beyond that :wink:
Ben

HAL

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Re: Servo amp issues
« Reply #8 on: 9 Dec 2018, 05:35 pm »
Ben,
The servo amp must be off and disconnected from the wall. 

Whichever wire is easier to disconnect is fine.  Just make sure it does not touch the terminal.

Take the resistance measurement across the two terminals with the ohm meter probes.

rockdrummer

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Re: Servo amp issues
« Reply #9 on: 1 Jan 2019, 09:29 pm »
Hi everyone. Happy New Year!

Here is some updated info on our sub issues. Some improvement. Took the driver out, sealed 12" sw-12-04. Tested the resistance of the coils.
They jumped around a bit, and my meter is pretty cheap, but the driver coil was around 8 ohms, and the servo coil was around 21 ohms.
Before we took out the driver there was some output but next to nothing. After getting the driver out, putting it back in and out again, I noticed the clip on the neg servo coil wire was loose. Only to find out the clip broke off. We hooked the wires up directly to the spring input with bare wire and the output was much more audible. Not where I think it should be, but an improvement. I checked the driver coil wire connectors and they seem fine.
Ran out of time so I couldn't hardwire the driver coils to the spring clips.

I guess we are happier with some clean output, but wondering if the measurements are as expected.

Thanks for any advice.
Ben

Danny Richie

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Re: Servo amp issues
« Reply #10 on: 1 Jan 2019, 10:59 pm »
The DCR of the driver coil should be between 3 and 4 ohms.

rockdrummer

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Re: Servo amp issues
« Reply #11 on: 2 Jan 2019, 12:25 am »
Thanks Danny. I would have to say depending on where I touched the lead to the terminal, it was a different reading. There may have been a low reading like that. I will need to get over there again and do more troubleshooting.
Ben