Dc offset... Help needed

[Blad09]

Hey PP, I have zx350, did a cap change along with output transistors gate resistors new thermal paste and new diodes on the B+. Amp fires up no prob plays great BUT, I checked dc offset, meter set to 200m and I'm getting +2.7mV on left ch and -97.7mV on the right ch. Looks too high on right ch but I'm not sure what to do next. Any suggestions? Thanks.


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[zeropoint0.5]

what transistors did you put in place, and why did you change the gate resistors but didn' change the fet's

in the powersupply ??? what is the value of the resistors you putted in place ??

and did you set the bias level again after changing components ??

[Blad09]

New power supply fet's, not output transistors... My mistake. I will dig my receipts out to find part #'s. There were blown gate resistors, blown diodes and a blown cap when I bought it and I was advised to do fet's as well as caps diodes and resistors. I dont know how to set bias so no havent done so. I will try and round up all my replacement parts and report back. Thanks!


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[zeropoint0.5]

New power supply fet's, not output transistors... My mistake. I will dig my receipts out to find part #'s. There were blown gate resistors, blown diodes and a blown cap when I bought it and I was advised to do fet's as well as caps diodes and resistors. I dont know how to set bias so no havent done so. I will try and round up all my replacement parts and report back. Thanks!


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from what you tell the amp has been reverse connected.....

normally if you replace the powersupply that doesn't affect the bias settings, but something else in that channel could be

blown or shorted and causing the high dc offset......

the 4 diodes are a 1N5401, the gate resistors must be 33ohm, the ps fets STP55NO6 or NDP7060

did you use something else ??

check output transistors in that channel on shorts................

[Blad09]

The diodes I put in are indeed the 1N5401, resistors are 33 ohm and the fets are NDP7060. I have checked the output transistors via the method on bcae1.com and they are good. The amp powers up fine and plays music on both channels, fwiw.


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[Blad09]

Is the dc offset going to damage speakers? Or the amp itself? In other words, what are possible symptoms? Should I be re-setting bias?


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[zeropoint0.5]

Is the dc offset going to damage speakers? Or the amp itself? In other words, what are possible symptoms? Should I be re-setting bias?


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i quess you understand it is not smart to use the amp until the problem is solved..... what you certainly can do in the mean while
is search after damaged transistors/diodes/resistors, maybe bad soldering points or traces,

it is diff to tell from distance.....

i maybe suggest you contact Eric D/ Valeks or somebody else and look for a solution to solve the problem......

[Blad09]

Ok thanks zeropoint!!! I cant afford to ship out and repair right now so back to the closet it goes lol


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[Blad09]

I have gone through the amp and as far as my knowledge goes (not very far lol) it seems good aside from the high offset


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