Hello,
I am having a strange issue with my MRV-1505.
When you first start the car the amp powers up normally.
If I cycle power of the car (remove remote signal and reapply) the amp will no longer power on. You need to wait ~10 minutes for the caps to discharge and the amp will only power back on with a 60% success rate.
The issue is completely eliminated if chassis ground is tied to signal ground.
When the issue is occurring the current draw is ~60mA and the green power light is lit.
I was wondering if there is a known fix for this issue. I have read other forums suggesting shorting chassis ground to signal ground. This method works but I have a slight ground loop after trying this. The amp works normally otherwise.
Thank you,
Steve
I am having a strange issue with my MRV-1505.
When you first start the car the amp powers up normally.
If I cycle power of the car (remove remote signal and reapply) the amp will no longer power on. You need to wait ~10 minutes for the caps to discharge and the amp will only power back on with a 60% success rate.
The issue is completely eliminated if chassis ground is tied to signal ground.
When the issue is occurring the current draw is ~60mA and the green power light is lit.
I was wondering if there is a known fix for this issue. I have read other forums suggesting shorting chassis ground to signal ground. This method works but I have a slight ground loop after trying this. The amp works normally otherwise.
Thank you,
Steve
Initially when I noticed the problem I was using a home built car pc with a schiit modi 3 dac inside. This dac isolates the signal ground from chassis ground.
In my other car I tried the amp in I have a Sony Xav-ax5000. Chassis ground is tied to signal ground from Sony so the amp works fine in this car.
Initially it also worked in the first car but now it does not.
In my other car I tried the amp in I have a Sony Xav-ax5000. Chassis ground is tied to signal ground from Sony so the amp works fine in this car.
Initially it also worked in the first car but now it does not.
I’m not sure entirely. There is ~1M ohm measured isolation between both points on the dac. I believe the dac is a differential signal internally until it comes out to the RCA output.
At one point I used an isolated regulator with an internal transformer to give me an isolated 5v ground. I ended up taking it out because the switching noise from the regulator was worse than the PC supply itself. There is still an optoisolator between the D+ and D- lines. That should have nothing to do with the isolated ground though.
At one point I used an isolated regulator with an internal transformer to give me an isolated 5v ground. I ended up taking it out because the switching noise from the regulator was worse than the PC supply itself. There is still an optoisolator between the D+ and D- lines. That should have nothing to do with the isolated ground though.
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The original version ran on 19v with an older i3 nuc motherboard. I had a cheap boost converter from Amazon to step the 12v up to 19v.
The nuc7i7 board runs from 12-24V so I run directly off battery power. I have an arduino controlled relay to sense ignition power to cut power to the nuc after car is off and nuc has completed a proper windows shutdown. Before adding this the nuc would draw ~80mA when off and eventually kill the car battery if the car sat for a few days. The arduino also has control to assert a 50ms power button pulse and it operates steering wheel controls.
The nuc7i7 board runs from 12-24V so I run directly off battery power. I have an arduino controlled relay to sense ignition power to cut power to the nuc after car is off and nuc has completed a proper windows shutdown. Before adding this the nuc would draw ~80mA when off and eventually kill the car battery if the car sat for a few days. The arduino also has control to assert a 50ms power button pulse and it operates steering wheel controls.
Yes PC ground is tied to vehicle ground.
The PC does not have any analog out. The only options for audio are a USB dac or HDMI.
The dac itself does not work when USB ground is tied to Audio ground. I think it may have something to do with the signal being differential.
The Alpine used to work okay with my setup for about 6 months. After it did not power on I opened it up and found ZD310 shorted on the power supply board. I replaced and the amp started to work in the current condition it does now. Initial power on is okay but if I cycle the key and don’t wait ~10-15 minutes it will not power back on.
I found the workaround of shorting chassis ground to signal ground by reading an online forum. It powers up every time but will not work in the original setup. Also in the second car there is a ground loop ~55hz that comes and goes based on engine rpm sometimes.
The PC does not have any analog out. The only options for audio are a USB dac or HDMI.
The dac itself does not work when USB ground is tied to Audio ground. I think it may have something to do with the signal being differential.
The Alpine used to work okay with my setup for about 6 months. After it did not power on I opened it up and found ZD310 shorted on the power supply board. I replaced and the amp started to work in the current condition it does now. Initial power on is okay but if I cycle the key and don’t wait ~10-15 minutes it will not power back on.
I found the workaround of shorting chassis ground to signal ground by reading an online forum. It powers up every time but will not work in the original setup. Also in the second car there is a ground loop ~55hz that comes and goes based on engine rpm sometimes.
I don’t have a ground loop isolator.
The dac output is single ended I was wrong about that. On the board they isolate usb shield from the RCA shield. The RCA shield has continuity to the Digital ground and analog ground vias on the board.
To use hdmi you would need to have a display with an internal dac/decoder or a separate dac/decoder as you mentioned. I don’t have either in this setup.
The dac output is single ended I was wrong about that. On the board they isolate usb shield from the RCA shield. The RCA shield has continuity to the Digital ground and analog ground vias on the board.
To use hdmi you would need to have a display with an internal dac/decoder or a separate dac/decoder as you mentioned. I don’t have either in this setup.
I don’t have a schematic for the dac. I found this pretty decent hardware description article online though: Hardware Teardown of Schiit Modi 2 USB DAC | Audio Science Review (ASR) Forum
The Dac that I have is actually a Modi 2 model. Not modi 3. I have a modi 3 for my home pc.
The Dac that I have is actually a Modi 2 model. Not modi 3. I have a modi 3 for my home pc.
Have you taken the board out and looked for damage with a lighted magnifying glass?
I don't think there should be an isolated ground and that's reinforced by the note by the author:
"Unfortunately my measurements show that such isolation does not exist in reality but at least whoever did the PCB layout, worked to do his part."
I don't think there should be an isolated ground and that's reinforced by the note by the author:
"Unfortunately my measurements show that such isolation does not exist in reality but at least whoever did the PCB layout, worked to do his part."
The alpine used to work before I did the power supply repair (replaced ZD310 and shorted chassis ground to signal ground).
I was wondering if there may be something I missed while troubleshooting the alpine as it did work without shorting chassis ground to signal ground previously.
The PPI works fine in the car. I just don't know how comfortable I am selling the alpine on eBay in its current state. It works fine on a bench test but when installed in my second car with the Sony (XAV-AX5000) head unit there was a horrible ground loop. In that car I replaced the alpine with a Kenwood KAC-7204 I have and there was no ground loop whatsoever.
The alpine is a beautiful and very well made amp. I would rather hold onto it and repair it. I just don't know what else I can try to fix the grounding issue it has.
I was wondering if there may be something I missed while troubleshooting the alpine as it did work without shorting chassis ground to signal ground previously.
The PPI works fine in the car. I just don't know how comfortable I am selling the alpine on eBay in its current state. It works fine on a bench test but when installed in my second car with the Sony (XAV-AX5000) head unit there was a horrible ground loop. In that car I replaced the alpine with a Kenwood KAC-7204 I have and there was no ground loop whatsoever.
The alpine is a beautiful and very well made amp. I would rather hold onto it and repair it. I just don't know what else I can try to fix the grounding issue it has.
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