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Old 4th October 2011, 02:22 PM   #1
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Default Digital designs Z2

I got one of theese amps in for repair.. After looking at it i dont really wanna work on it so i was gonna send it in to get fixed..

I called around a few places yesterday..


1 place i called asked what the amp was doing and i told him that it powers up and idles perfect just no sound..

I checked it and there no rail to rail oscillation..

He told me that the driverboard is bad. I then told him that the driverboard is brand new never used..

So then he told me that if the 33 ohm gate resistors for the outputs do not read exactly 33 ohm the amp will not oscillate..

He said if they measure 33.5 ohms 32.5 ohm ect and not measure exactly 33 ohms the amp will never work..

Just wondering if anyone knows if there is any truth to this??
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Old 4th October 2011, 04:27 PM   #2
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This is unlikely to be true but he may know something that I don't.
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Old 4th October 2011, 08:53 PM   #3
luka is offline luka  Slovenia
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gate resistors have nothing to do with oscillation...anyway, what do you have (osc? dvm?) and what did/could you measure? did you call DD, which should be the first thing?
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Old 4th October 2011, 09:25 PM   #4
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I have both o-scope and multimeter

I havent measured anything as of yet.. I got the amp in and the guy told me that another repair shop said it wasent oscillating..
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Old 5th October 2011, 06:04 AM   #5
luka is offline luka  Slovenia
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apart of calling DD and getting a quote on how much would it cost...

Start with basics, chech if there is short on input, if not, chech if there is one on remote. I will assume for now, that there isn't one. Next start with gates of supply, check with scope, if there is square wave on them, if not, trace the circuit back to driver board, see where you can find such signal. If there is not one, even when you are on driver board (I think main ic SG or TL is on there), check if that is gets supply voltage, and all other pins have right voltage on them (do not assume driver board is ok, even if brand new (I don't know where you got if from))

Btw, if there is PWM (square wave) on power supply gates (on each one) check is supply is making high voltage (you will run amp without heatsink by then, so don't load it with any loads...)

post anything here, and will go from there on
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Old 7th October 2011, 03:14 AM   #6
ppia600 is offline ppia600  United States
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I would use 1% resistors just to try, they're not expensive. At least you'll put his theory to the test. Of course I'm not an expert on these things, I have to ask people here for help. One of them is in this thread, lol.
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Old 7th October 2011, 03:35 AM   #7
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Ok i talked to another repair place and they said they also fixed alot of Z2's and the resistors have nothing to do with it..


I forgot to ask them the other thing i was wondering..


I noticed that all of the outputs in this amp DO NOT have the same date codes on them..


Would that cause the amp not to oscillate ???


Just wondering i know for long term i need to get all the outputs replaced but as far as testing goes wondering if the outputs dont have all the same date code if that may cause problems?
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Old 7th October 2011, 04:07 AM   #8
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That shouldn't make any difference, you worry about that when loaded. One will carry more load than the others possibly if they are from different batches.

Look for the heart of the amp which is usually the 494 or equivalent chip and check the signals as luka said.
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Old 7th October 2011, 06:44 AM   #9
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So will it hurt anything if i power this amp up without the audio driverboard in it??
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Old 7th October 2011, 10:30 AM   #10
luka is offline luka  Slovenia
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1% will do nothing, as don't different dates of fets... this is not AB amp
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