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Old 20th October 2013, 11:57 AM   #1
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Default Bose 901 Series IV ActiVe EQ schematic

Does anyone have a copy schematic for the above Bose Series IV EQ? I want to recap the one I have and someone else has been in there and changed the main filter caps. I want to make sure they are the correct ones that were installed. The one that they installed are 50V 470uf. Can anyone verify this is correct?

I have searched the forum and Google but I can only find ones for older units.

Last edited by daveyhockett; 20th October 2013 at 12:08 PM.
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Old 30th November 2013, 09:12 AM   #2
ctef is offline ctef  Bulgaria
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Change them. Bigger is better.
Also, change and all other electrolytic. Use Elna Silmic. Rise them 5mm over PCB.
The first one in the chain is especially sensitive to the noise. If You don't know which it is, try with a naked finger on the top of capacitors, system working, and You'll hear
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Old 11th December 2013, 11:55 PM   #3
Jsixis is offline Jsixis  United States
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what series? I have a stock series II that I need to re cap soon and I could take it apart and look if you need the series 2 version.
I'm for leaving things stock myself. I have read a couple of pages where people have changed things because "they" thought they could improve it
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Old 12th December 2013, 12:51 AM   #4
kevinkr is offline kevinkr  United States
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Please see thread title..
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Old 12th December 2013, 06:37 AM   #5
ctef is offline ctef  Bulgaria
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Quote:
Originally Posted by Jsixis View Post
what series? I have a stock series II that I need to re cap soon and I could take it apart and look if you need the series 2 version.
I'm for leaving things stock myself. I have read a couple of pages where people have changed things because "they" thought they could improve it
In Series I&II, is better to exchange the input capacitor and capacitor in the feedback with no electrolytic capacitors. It helps.
To see which they are, use scheme
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Old 12th December 2013, 09:52 PM   #6
Jsixis is offline Jsixis  United States
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opps sorry totally missed your looking for a 4.

https://lh6.googleusercontent.com/-h...1-I-Second.png series 1 schematic for posterity

Series 2 | KF7LZE's Blog <---this guy may be able to help you
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