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Old 24th December 2010, 06:25 AM   #1
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Default Digital Designs Z2

I got this amp in for repair and well someone tryed repairing it themselfs.

I pulled all of the power supply fets out of the amp and the output driver board also .

With the power supply fets in the amp the amp trys to power up and the Transformers start squealing like crazy.

With the power supply fets out of the amp heres what i have for gate signals
There are 4 banks of fets first pic is bank 1 and pic 2 is 2nd bank Pic 3 is the 3rd bank and last is the fourth bank. If you notice 1 of the banks deflects much higher then the other 3 and another bank doesnt look the same as the other 2

ANY Ideas?
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Old 24th December 2010, 06:25 AM   #2
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Heres the last bank
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Old 24th December 2010, 06:29 AM   #3
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Lets see some pics of the hardware, what do you see first that looked like it was touched? Check your joints, and dont be lazy, verify all the resistor value's fall in line with the color bands, and make sure you dont have any obvious shorts on any switching devices. Whilst wave forms and signals rule the logic world, amp repair can be done at the lowest level, verify no shorts (open or closed) and check your discrete components...



as my father once said, "what happens on one end is likely caused by a problem on the other end!"
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Old 24th December 2010, 06:40 AM   #4
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Ive checked all that The gate signals dont look right to me And everything has been touched First i wanna get the supply up and running correctly then the output section. Ive been messing with amps over 10 years so i know about the rsistors and such.
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Old 24th December 2010, 06:51 AM   #5
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If that's the case, then disconnect the smps from the amp side, and, as you say "get it up and running" aka remove the final rectifier's and you shall obtain your goal, strange change in amplitude on the 4th pic, hows that op-amp look? voltage look good?



also, that BNC connector on your scope looks jacked up... might want to fix that.
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Old 24th December 2010, 06:57 AM   #6
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Not trying to be rude at all But have you fixed theese big amps?
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Old 24th December 2010, 07:06 AM   #7
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I'm a network engineer, with a master's in electrical engineering from cal-tech. Yes I fix complex, high level logic systems, as a cisco CCIE for the state of nevada.


I'm here to help, and be helped.
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Old 24th December 2010, 07:06 AM   #8
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he is right, you need running supply first, then you need to see if output is working ok

Check if gate drives are ok, check what voltage amp makes, should be pretty high
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Old 24th December 2010, 07:29 AM   #9
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I understand that i need to get the Power supply up and running first off. The gate drive signal dosent look right on 2 banks of the power supply fets. I dont know what pulling the rectifiers would do besides eliminate the output section which is already done THe problem is with the Power supply drivers or driver card
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Old 24th December 2010, 07:38 AM   #10
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the entire output section has power if the final rectifiers are in-place, pulling them in most cases, will isolate the smps in it's entirety. Old amps had the V+VgV- isolated down to just the 3 traces, seporateable by jumpers in most cases, so isolation was easy, these days and on some amps, making isolation a priority, can be a pain! But were here to help



so, I have to ask, whats "big" to you, Mike? I have fixed hifonics xxx's in the 10kw range, I dont see much larger then that these days, do you work on industrial RF heaters? cause that stuff's way neat! My most complex is my millet 300b 5.x system for my home theater.



Or the Intel itanium ES machine's I have to evaluate sitting @ my office.
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