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Class D Switching Power Amplifiers and Power D/A conversion

Ground Zero GZPA 1.4K-HCX
Ground Zero GZPA 1.4K-HCX
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Old 14th July 2019, 10:44 AM   #1
tobi320i is offline tobi320i  Germany
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Default Ground Zero GZPA 1.4K-HCX

my Ground Zero GZPA 1.4K-HCX amp only works with 11,5V and below.when i increase the voltage,the amp goes into protect.


the pin 4 of the 494ic is then 4,3V


what could cause this?
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Old 15th July 2019, 05:28 PM   #2
tobi320i is offline tobi320i  Germany
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nobody an idea?


there is a direct connection between the power supply driver board and the output driver board,marked with the red arrows.


there i read 2V. on a second,good working amp,i read 0,1V there.
everything on the bad amp works,it only changes into protect mode when the input voltage is higher than 11,5V


please help
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Old 15th July 2019, 11:30 PM   #3
Turbowatch2 is offline Turbowatch2  Germany
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Some voltage limiting diode gone? If you have two amps and such a "friendly fault", you just need time to narrow in on it. If possible, change modules from side to side, amp to amp, so you can rule out most parts of the cirquit.
Then measure good side, bad side, while turning supply voltage up. Should be just a matter of time.
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Old 17th July 2019, 07:15 PM   #4
tobi320i is offline tobi320i  Germany
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i told with the previous owner today.i bought 2 of these amps from him.he said both amps were connected in linkmode.
on a dB drag event,both amps said goodby.

so one amp is ready again,two OPs in the pre-amp section were dead.
the second one is still in protect but i made an interesting discovery.
when i connect speaker minus of the bad amp with speaker minus of the good amp,no protect anymore,even on 14V


I dont know what else to measure
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Old 17th July 2019, 09:56 PM   #5
Turbowatch2 is offline Turbowatch2  Germany
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You are doing funny things. Most people would do anything, but connect speaker outputs from different amps, if they donīt have a clue about it. Maybe you play a little bit, more than really repair?
Negative marked outputs on an amp donīt need to be real negative, in the sense of ground. Check both amps SEPARATE for contact from negative (battery ground) to negative loudspeaker out, if you have a digital voltmeter. If the working amp has a solid zero ohm connection and the brocken one not, there is something wrong with that.
Maybe the brocken amps output voltage that triggers PROTECT for a very important cause (!!!) is absorbed by the working amp. This is NO cure! Just a funny technical effect.
Do you have Oscilloscope and tone generator? If not, sell to ebay as long as you have not totally destroyed them...
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Old 18th July 2019, 04:14 AM   #6
tobi320i is offline tobi320i  Germany
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Quote:
Originally Posted by Turbowatch2 View Post
You are doing funny things. Most people would do anything, but connect speaker outputs from different amps, if they donīt have a clue about it

i have a scope and i have a tone generator....



do you know what link mode is?you connect two amps(master and slave) to one big amp.for this,you need to connect minus of the amps speaker terminals.....


when they work in link mode,the bad amp stays on, even on 14V
is that not nice to know?
whats to do now?
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Old 18th July 2019, 09:25 AM   #7
tobi320i is offline tobi320i  Germany
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between batt minus and speaker minus i read 0V on the good amp and 2V on the bad amp
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Old 18th July 2019, 11:33 PM   #8
Turbowatch2 is offline Turbowatch2  Germany
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So there ist your problem. You have to walk back and compare good amp to bad amp. Somewhere you will see same values at both amps. So, after that stage is your problem. Take your scope to look at each part. Use a very fine pin with the scopes probe, one that has non conductive material around it. With a longer metal needle you will easily make a short if you slip, something that always happens. Donīt ask me how I know...
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