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Infinity ServoStatik - need help with subwoofer

Hello, I'm trying to resurrect an old ServoStatik I and the midrange and tweeters are working.

However, there is no sound whatsoever from the subwoofer.  I did a continuity test on the cable and it seems fine.  Is there an easy test I can do to tell whether the problem is in the amp or the subwoofer?

I tried testing for resistance in the connectors to the bass commode (with no luck) but now I'm trying to decide whether to take apart the amp/crossover or the commode.

Thanks,
Mark

pyite
pyite OP
28 posts
 
I took the crossover/amp apart and it looks clean enough... nothing obviously broken. So I guess it is time to look at the subwoofer.

I have never tested amps like this, so let me ask what is probably a dumb question: should I be able to do a voltage test on the output to the sub while some bass-heavy music is playing?

Obviously I don’t want to short the signal and servo pins... but will the amp send a signal at all if the servo part isn’t connected? It isn’t easy to find known-good ServoStatik parts to use for testing!

Post removed 
pyite OP
28 posts
 
Thanks for the suggestions!

After running through some of your tests, it looks like the main problem was 50 years of oxidation on the pins connecting amp and subwoofer. I used a file to scratch all of the pins and after that then I was able to measure ~5 ohms. I unplugged one of my Kappa 9’s and connected the cable to the sub and was able to hear audio... awesome!

The resistance varied quite a bit when I moved the cone. I was able measure both the signal and servo paths, though it looks like the servo resistance varied a lot more. I’m assuming this is a good sign.

Tonight I’ll hook everything up and everything should be working properly. Thanks for the hints.


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