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Old 11th December 2007, 04:04 AM   #1
Itsme is offline Itsme  United States
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Default Built in Sub amp problem.

Hello.. I know this isn't really car audio, But anyway,I have a Venturi V1220 Subwoofer with built in 200 watt amp. It quit working so I took it apart and found a burnt resistor. I don't know what size to replace it with. Rings are burnt off. Does anybody have a schematic to similar amp board? Or a lucky guess? Looks like a pretty basic amp.
Also there was 2 what I think are ceramic caps on either side of the resistor, And all I can make out on those are 104.
Can anybody help???
Also I followed the resistor board traces back to the Big transformer if that helps?

Here are some pictures.

Thank you!
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File Type: jpg sub 05.jpg (79.0 KB, 60 views)
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Old 11th December 2007, 04:05 AM   #2
Itsme is offline Itsme  United States
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Here is a picture of were I have removed the bad resistor and the ceramic cap next to it.
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File Type: jpg sub 02.jpg (91.4 KB, 57 views)
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Old 11th December 2007, 04:06 AM   #3
Itsme is offline Itsme  United States
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Quote:
Originally posted by Itsme
Here is a picture of were I have removed the bad resistor and the ceramic cap next to it.
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File Type: jpg sub 04.jpg (22.8 KB, 53 views)
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Old 11th December 2007, 05:10 AM   #4
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If you're not used to working on AC mains equipment, you should not work on this without an isolation transformer. When powered up, this amp will have 120v AC and more than 170v DC (it appears to use an offline switching supply) on much of the board. If you're grounded in any way and come in contact with any of those components, it can take you out of the gene pool.

Without a variac, powering it up could be dangerous. High voltage can make components fail explosively.
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Old 11th December 2007, 06:20 AM   #5
Itsme is offline Itsme  United States
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Quote:
Originally posted by Perry Babin
If you're not used to working on AC mains equipment, you should not work on this without an isolation transformer. When powered up, this amp will have 120v AC and more than 170v DC (it appears to use an offline switching supply) on much of the board. If you're grounded in any way and come in contact with any of those components, it can take you out of the gene pool.

Without a variac, powering it up could be dangerous. High voltage can make components fail explosively.

Yes, i understand that. I am just wondering if there is a way to mathamaticaly figure resistor size or if this might be just a generic style chip amp that somebody is famillar with and might know where to find schematic?
I apologize for not putting the daughter card pic's up. I was thinking it was preamp only.
Here are some pic's. I hope they help.
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File Type: jpg sub daughter board 01.jpg (74.8 KB, 44 views)
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Old 11th December 2007, 06:31 AM   #6
Itsme is offline Itsme  United States
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I am a service tech in the commercial HVAC trade and have unfortunetly been zapped way to many times in my 30 year's in this field. So trust me when I say, I will be very careful.

But I sincerely thank you for the warning Perry.
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Old 11th December 2007, 06:33 AM   #7
Itsme is offline Itsme  United States
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