Bose 901 Series III Losing Power/Shorting in and Out - AVS Forum
Speakers > Bose 901 Series III Losing Power/Shorting in and Out
meekstape's Avatar meekstape 09:46 AM 10-04-2011
So I am aware that the Bose 901's are a love/hate sort of thing for some people. With that said, I picked up a pair for a really good price with the active EQ and refoamed the surrounds and all went really well.

However, when I tested last night, one the cabinets was cutting in and out. It was like it was losing power. This didn't happen at first. All seemed fine when i first hooked up. I first noticed that it was a lot lower output than the other one and when i turned it up, it hit a ceiling and popped and the volume cut dramatically. And with every bass hit, there was a slight 'crack sound' I could hear it wanting to play full range, but it was cutting out. Could this be some loose connections? I'm really just hoping that there's no blown speakers to be honest.

Has anyone ever rewired a pair of Bose 901's? I can't find any information online of anyone doing this. Surprising really, considering how many people restore these things and how short the wiring is in these things.. Anyhow, any insight would be much appreciated. And maybe keep the 'Bose-Bashing' to teeny minimum?

Ratman's Avatar Ratman 11:40 AM 10-04-2011
1) check speaker wire connections.
2) check audio cables between the equalizer and amp.
3) are you sure the equalizer is not at fault?
4) check for a bad driver(s) surround
donutfan's Avatar donutfan 01:56 PM 10-04-2011
Originally Posted by Ratman View Post

3) are you sure the equalizer is not at fault?

This receives my vote for most probable cause of the effect he is hearing.

According to Bose's online manual for this series, it was sold back in 1976 and imo some of the components in the EQ have probably aged enough to cause problems. Capacitors are notorious for doing this, especially larger electrolytic types (power supply-related ones in particular) because they can leak in turn causing their electrical value to change or to compleltely malfunction.* I have seen people on other forums write that they replaced these and their EQ worked fine but there *are* other components that can go bad, so it may not always be that simple to repair the EQ.

Also, the manual mentions (it would not allow me to copy/paste the exact statement) that if the EQ is suspected of causing a problem, disconnect it from the signal path. To me that means play the speakers without the EQ which helps eliminate at least one variable from the problem.

* this is also usually why so many older speakers sound so "soft" because their crossovers' aging capacitors are not allowing the full amount of power to reach the tweeters and midrange drivers
meekstape's Avatar meekstape 10:17 AM 10-05-2011
Somehow, it's not happening anymore. I did actually take the EQ out of the signal path before when it was happening continuously, and still did it.. Weird thing that I think possibly had something to do with : the fuse for the front left channel (speaker channel in question) wasn't blown, but was very very slightly split. I replaced it and now all seems good. Anyhow, I took out all the speakers and checked the connections and re-secured them. I think it's ok. I'll keep testing and see what happens! Really appreciate the help!
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