Working on the Steg K1-5000, class d amplifier has blown. Mosfets and drivers are defect.
Just left from the mosfet gate driver MIC 4421 there is another part which is unknown to me:
0600 1418 ZNJ 8 pins IC
Any info for this part available?
Just left from the mosfet gate driver MIC 4421 there is another part which is unknown to me:
0600 1418 ZNJ 8 pins IC
Any info for this part available?
I think I found it:
HPCL 0600 optocoupler
https://docs-emea.rs-online.com/webdocs/0d1f/0900766b80d1f17b.pdf
HPCL 0600 optocoupler
https://docs-emea.rs-online.com/webdocs/0d1f/0900766b80d1f17b.pdf
Still working on this amplifier.
Exchanged power supply mosfets and drivers, thats working OK railvoltage +/- 75V. Class d part is still not ok.
On the image above you see on the left part HPCL0600 optocoupler, right the MIC4421 gatedriver and then the smd transistor part 2F connected to the source of the output MOSFETS.
When looking at the smd code 2F this can be NPN or PNP, this is the PNP MMBT2907 or PMBT2907 a few were ok, so I could measure them to be sure. I had 2G on stock this is a MMBTA56 so I used these 12x . Mounted also 12x new mosfets in the output IRFB4228 and defective gate resistors 18R.
When testing the amp without load it is working normal, unclipped output about 55V.
With load I get a distorted output signal above 17V @ 2 ohm, about 145w rms. See images. Ever seen this kind of distorsion...? I measured pulses at the gates but because of the feedback I measured this distorsion everywhere. Could this caused by the other transistors 2F <> 2G..don't think so, or leaky mosfets or...??
Exchanged power supply mosfets and drivers, thats working OK railvoltage +/- 75V. Class d part is still not ok.
On the image above you see on the left part HPCL0600 optocoupler, right the MIC4421 gatedriver and then the smd transistor part 2F connected to the source of the output MOSFETS.
When looking at the smd code 2F this can be NPN or PNP, this is the PNP MMBT2907 or PMBT2907 a few were ok, so I could measure them to be sure. I had 2G on stock this is a MMBTA56 so I used these 12x . Mounted also 12x new mosfets in the output IRFB4228 and defective gate resistors 18R.
When testing the amp without load it is working normal, unclipped output about 55V.
With load I get a distorted output signal above 17V @ 2 ohm, about 145w rms. See images. Ever seen this kind of distorsion...? I measured pulses at the gates but because of the feedback I measured this distorsion everywhere. Could this caused by the other transistors 2F <> 2G..don't think so, or leaky mosfets or...??
Last edited:
With 4 ohm (resistor) the same issues at higher output voltage, on 1 ohm at about 9V. Is not going in protection, but í'm carefull with it, so swiching off when distorsion is visible.
I have two of these amps overhere, they were linked for SPL competition. One is good working. Exchanged the class d driverboard from the bad amp the good one, and then it's working ok also. So, driverboard from the bad amp should be ok.
I have two of these amps overhere, they were linked for SPL competition. One is good working. Exchanged the class d driverboard from the bad amp the good one, and then it's working ok also. So, driverboard from the bad amp should be ok.
Last edited:
I'm trying to find more info on this amp or something similar. If no one comes along that can be of more help, I may need you to post a high resolution photo of the driver board where all of the component values and the IC part numbers are legible.
Thank you Perry. I exchanged the small piggyback driverboard to another amp and it's working normal in that amp.
Just some thoughts...the distorision is only on the positive side of the signal (or negative with polarity of speakerwire changed). And with a load. I think I change the optocouplers 0600 and MIC4421 for second time. Problem is that I have to rebuilt it completely before I can test it, clamp mosfets etc.
Just some thoughts...the distorision is only on the positive side of the signal (or negative with polarity of speakerwire changed). And with a load. I think I change the optocouplers 0600 and MIC4421 for second time. Problem is that I have to rebuilt it completely before I can test it, clamp mosfets etc.
At 4 ohm load the distorsion started also at about 17Vrms output. Changing again of the optocouplers and MIC4221 makes no difference.
The over-current protection appears to be on the main board. Can it react quickly or is it a latching circuit?
Do you see any reaction to the output of the protection that corresponds to the notches in the sine wave?
Do you see any reaction to the output of the protection that corresponds to the notches in the sine wave?
Without circuitdiagram I decided to stop this repair, via the distributor this amp is send to GTtrading for repair. 😡😱
It appeared that the driver IC MIC4421 was defective again. I had a batch faulty IC 's i think. After changing the MIC4421 it was working normal again.
Last edited:
- Status
- Not open for further replies.