Aragon 4004 Bias and DC Offset Adjustment

Aragon 4004 Bias and DC Offset adjustment http://forums.klipsch.com/forums/thread/904785.aspx 24 Apr 07

FIRST POST

Here's how you would check/adjust the bias and DC offset:

1. Place a voltmeter across any of the emitter resistors. Adjust bias adjustment pot. for a reading of 10mV +/- 2mV. Repeat for the other channel.

2. Short the input, place a voltmeter across the output of the shorted channel. Adjust DC offset pot for a reading of 0.00VDC +/- .01V. Repeat for other channel.

3. Allow amp to burn in for a minimum of 4 hours. Then remove signal and allow to idle for 20 minutes. Repeat steps 1 and 2.

I'll try to describe the position of the pots you'll need to adjust. The bias pot is located more toward the middle of the board in between the 8 emitter resistors, pretty close to them. The DC offset pot is located more toward one side of the board more away from the emitters than the bias pot. I hope this helps.

Steve Donalson Aragon / Acurus / Klipsch / Jamo Technical Support Specialist 1-866-781-7284 Aragon 1-800-554-7724 Klipsch 1-877-456-5266 Jamo

SECOND POST

Steve,

After a very long time I finally am getting around to this. So far I have used my outlaw ICBM and have not had that noise, but this one will go now so time to do something, picture attached :-)

I have peeked into the mighty 4004 and it seems I need to give it a little cleaning but I could not resisit to try some measurements. I take it the components I have encircled in red are responsible for the bias ?

So I put the voltmeter to the legs of the emitter resistors and after some adjusting measured something around the high 7s to the low 12 in voltage. There is quite some variation in between the resistors and it seems the middle value is pretty close to 10mV, that Ok ?

Now I would have to adjust DC offset, that is the blue encircled pot ?

Thanks Oliver THIRD POST That should be fine and yes the one circled in blue is the D.C offset pot

Steve Phillips Senior Home / Professional Tech Support Klipsch Audio Technologies 1-800-554-7724 option 2 for Tech Support, option 2 for Home Audio

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