Topic: Hey electrical gurus, help me trouble-shoot my old Infinity RS4Bs

[Gutbucket]

The tweeter on one of my mid 80's era Infinity RS4B stopped working completely yesterday.  It's not a blown EMIT element (I took the tweeter out and measure it at about 4 ohms, looks & smells fine) or the L-Pad pot (they are all scratchy and intermittent, but work and both in this speaker measure OK with the ohmeter).  I suspect the mystery component photographed below is a fuse or circuit breaker that died.  I measured across it in the circuit with the ohmeter and it measures 20+Mohms (meter keeps creeping upwards).

Here's the mystery component, about the size of a quarter-

[Gutbucket]

Some shots of the speaker and x-over-

[Gutbucket]

Close ups of the more recognizable components-

[Gutbucket]

Cool, found the published x-over circuit.  The mystery component does appear to be a fuse of some sort.  I guess that's obvious from having 1A 30 printed on it.. is that one amp, thirty volts?  I'm assuming such a high resistance measurement means it's dead and needs replacing. I could open up the other speaker and measure it to be certain I suppose. Suggestions for replacing this component?  Here's a PDF of the technical sheet on the speaker with the x-over circuit-
 

[Lil Kim Jong-Il]

Try contacting infinity.  Its been a long time but when I needed to replace drivers in my RS6bs they were very helpful, sent me schematics and replacement drivers and there was a tech who actually knew about the vintage models.

Sexy speakers BTW.  I sure enjoy seeing those still in use.

[notlance]

20M is for all intents and purposes an open circuit.  Don't know if the component in question was a fuse, but it has become one.  Since it's in series with the + input, just short out the components leads and you should get your tweeter back.  You could replace the "fuse" with a similar component, add an external fuse holder or just leave the "fuse" shorted.  Fuses usually don't act fast enough to protect tweeters anyway, but perhaps EMT tweeters fail in a manner different from "normal" tweeters.  (I'm no expert on EMT tweeters.)

[JD]

Looks like that component says Culver. Might be made by Foster Culver whom makes audio equipment including speaker crossovers. Might be worth contacting them.

http://www.fosterculver.com/Electronics%20Page.htm

[Gutbucket]

Thanks for the input, guys.  Perhaps it's some sort of fast-acting circuit-breaker that is more effective protection than a fuse.  Those EMITs are getting harder to find these days so I hesitate to bypass it and risk smoking the tweet.  I'm sending an e-mail off to  Foster Culver with a photo (and Inifinity once I find an address) and will go from there.

[edit- Just noticed the lettering style of 'Culver' is the same on the website and the component.  Thanks JD, good eye.]

[Gutbucket]

Reply from FosterCulver-

Hello,
I wish that we could help you find a replacement for that old Culver part, but unfortunately, we no longer build those parts. I think that you may have to keep searching the internet for a parts supplier or distributor that may offer something close to what your part is. Unfortunately, no one here knows what that part is because all the old Culver people are no longer with our company. Best of luck though. I hope you find your part.

Best regards,

No reply from Infinity so far.  Anyone aware of a fast acting circuit protector that may be an appropriate substitute?

[live2496]

Found this through googling. Calibrated light bulb
http://www.eden-electronics.com/info/articles/tweetertext.htm

[Gutbucket]

Interesting, thanks for the link.  Wondering how I would determine what light bulb would be a correctly calibrated match. Time to open up the other speaker and figure a way to measure the working component.. light bulb replacement or otherwise.