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
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!

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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.