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Old 1st November 2009, 12:05 AM   #1
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Default fosgate g250_a2 bias problem

ok,

down to a problem with getting the right channel to bias correctly. currently, the base of q212 will only adjust 1.7 to 2.0 volts.

any suggestions?

p.s.

perry, did you get my email?
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Old 1st November 2009, 01:16 AM   #2
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Does the channel work properly otherwise?

When did you email me?

What was in the subject line?
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Old 1st November 2009, 07:50 AM   #3
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hey perry,

alright, the right channel is the problem child.

i have a 1v p-p signal being applied.

the first pic is the left channel output, 10v p-p.

the second pic is the right channel with same input applied but at 2 volts per division.

i have 4 ohm resistors on the output.

i'm a little baffled right at the moment.
Attached Images
File Type: jpg IMG00007.jpg (60.7 KB, 35 views)
File Type: jpg IMG00009.jpg (56.1 KB, 35 views)
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Old 1st November 2009, 11:09 AM   #4
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Lift D204. Does that allow the bottom half to swing below 0v?

If not, what have you replaced in the right channel so far?
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Old 1st November 2009, 01:40 PM   #5
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hey perry,

lifted D204, and have a full sine wave on the output, but with a 5.2v p-p value with same input conditions as listed above.

also have not replaced anything yet.

Last edited by toobnoob; 1st November 2009 at 01:44 PM.
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Old 1st November 2009, 01:57 PM   #6
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perry,

replaced q216 as it was shorted base to collector. resoldered d204 and now have a full 5v-pp sine on the output.

Last edited by toobnoob; 1st November 2009 at 02:03 PM.
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Old 1st November 2009, 02:39 PM   #7
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belay that last post about the 5v p-p output, i apparently had the left channel gain set up higher than the right channel.

both outputs look good. now to adjust the bias.

got the bias adjusted.

eta:

pic is the left and right output at 5v per div.
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File Type: jpg IMG00011.jpg (80.8 KB, 26 views)

Last edited by toobnoob; 1st November 2009 at 03:07 PM.
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Old 1st November 2009, 05:35 PM   #8
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What do you think this is, a self-service forum? You're supposed to make us feel like you need our help. :)
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Old 1st November 2009, 06:55 PM   #9
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Quote:
Originally Posted by Perry Babin View Post
What do you think this is, a self-service forum? You're supposed to make us feel like you need our help.
lol...

hey perry, thanks so much for the assistance.

trust me, i am sure i will asking for more help!
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