Hello, i own a DD Z1a. I have bought this one damaged. As i have opened, i found Power supply Fet´s and Audio Fet´s burned. I have repaired all of them. Changed also the Capacitors in front of the Fets from Power supply and resistors.
The only problem was the Driver Board for the Audio part.
So in that way i had to send it for service. The Service repaired for a lot of money. I got it back, an it was working for about 40 minutes. Full load was also no problem.
After about 40 min., the Audio Fets burned again. I send it back to service, to recheck. They changed the Fets an drive board (Audio Side) again, tested, and after 40 minutes the Parts burned again. The tried twice.
They expect the Coils(transformers) from the digital audio part, but cannot proof or change because not longer available.
In round about two weeks i got the amp back and would try it myself again. Does anyone had this problem allready and can advice?
Anyway i will take of the coils and put them in a bath with varnish for electromotors. If there will be a problem with this coils it should be done with this.
Best regards from Germany
Achim
The only problem was the Driver Board for the Audio part.
So in that way i had to send it for service. The Service repaired for a lot of money. I got it back, an it was working for about 40 minutes. Full load was also no problem.
After about 40 min., the Audio Fets burned again. I send it back to service, to recheck. They changed the Fets an drive board (Audio Side) again, tested, and after 40 minutes the Parts burned again. The tried twice.
They expect the Coils(transformers) from the digital audio part, but cannot proof or change because not longer available.
In round about two weeks i got the amp back and would try it myself again. Does anyone had this problem allready and can advice?
Anyway i will take of the coils and put them in a bath with varnish for electromotors. If there will be a problem with this coils it should be done with this.
Best regards from Germany
Achim
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Hello Perry, until now i havent back the amp. But when i repaired there was nothing burned, or better i couldnt see because everithing was black from burned fets and capacitors. When i got the amp back i will check it.
Also what makes me a little confused: At the testbed, the amplifiers was measured with 4322 Wrms 0,95 Ohm 13,9Volt. Looks a little bit less than it should be.
Also what makes me a little confused: At the testbed, the amplifiers was measured with 4322 Wrms 0,95 Ohm 13,9Volt. Looks a little bit less than it should be.
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So, received my amp back. First opening shows, that the Audiopart is damaged. Removed the parts, and run the Amp without Audio Fets an Dig. Controllboard.
Powering up and have a Rail Voltage from 144V DC. I saw, that i have one burning mark on the Heatsink below the Mainboard in the height from the Audio section. Maybe the board had contact and damaged this...
Anyway, you can see on the Pictures, that i have changed the brown foil capacitors from the Powersupply with mkp type, because all of them was open as i received the amp first time. I think i will try to heat the transformers with a hairdryer to see if something happen with the railvoltage.
Powering up and have a Rail Voltage from 144V DC. I saw, that i have one burning mark on the Heatsink below the Mainboard in the height from the Audio section. Maybe the board had contact and damaged this...
Anyway, you can see on the Pictures, that i have changed the brown foil capacitors from the Powersupply with mkp type, because all of them was open as i received the amp first time. I think i will try to heat the transformers with a hairdryer to see if something happen with the railvoltage.
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Ok, so i put the board back in the heatsink, and clamped the Power supply mosfets. Run with 13,2 Volt input and got a Rail Voltage from 165V. Is this normal? Maybe because of missing Parts in the Audio section? The Capacitors can handle only 160V, so if i go up with the inputvoltage i expect, that the rail will rise more.
I tried also to twist and press the transformers, but nothing happen. Everything looks allright. The Transformers got allready temperature ( Handwarm). Still the same. Railvoltage is steady at 165V.
I tried also to twist and press the transformers, but nothing happen. Everything looks allright. The Transformers got allready temperature ( Handwarm). Still the same. Railvoltage is steady at 165V.
Hello again, the spare parts arrived, so i continued. Repaired the drive board for the audio section, installed new fets for audio section and give 12V on the amp, without rectifiers mounted. I got no Signal on the audio fets. Drive a strong 50Hz signal into the amp, the same. After that i installed the rectifiers and the amp draw execissive current. Two fets in audio are damaged, not blown.
Dismounted the rectifiers and fets for audio, give 12V, the Amp goes into protect. Dismounted the drive board aggain and checked:
Pin 2 and 21: I give +12V
Pin 13 i give +12V
Pin 16 i give -12V
Pin 14 i give +5V
Pin 15 i give 50Hz TTL signal.
Oscilloscope is showing this on Pin 29 and the most other Pins.
Also what i found on that drive board is, if i check the voltage between Pin 16 ( -12V) and the Diodes D1 D5 D6 D3, at the Diodes D1, D6 and D3 i have 12,4V , at D5 only 11,9V. Is the Diode still in range or should i replace?
Dismounted the rectifiers and fets for audio, give 12V, the Amp goes into protect. Dismounted the drive board aggain and checked:
Pin 2 and 21: I give +12V
Pin 13 i give +12V
Pin 16 i give -12V
Pin 14 i give +5V
Pin 15 i give 50Hz TTL signal.
Oscilloscope is showing this on Pin 29 and the most other Pins.
Also what i found on that drive board is, if i check the voltage between Pin 16 ( -12V) and the Diodes D1 D5 D6 D3, at the Diodes D1, D6 and D3 i have 12,4V , at D5 only 11,9V. Is the Diode still in range or should i replace?
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