How to confirm if mainboard inside max Series inverter is normal
Boost Circuit and DC-AC circuit have some IGBTs, they bear large current, if mainboard can’t work, most of time, it is caused by them, so when you suspect that mainboard is faulty, you can test them.
Turn to Diode position on multimeter
![](https://www.amosplanet.org/wp-content/uploads/2022/12/16710762971.png)
BUS+, BUS- Position
BUS Voltage is produced by BOOST Circuit on mainboard and imported into IO Board BUS+, BUS-
![](https://www.amosplanet.org/wp-content/uploads/2022/11/image-8-1024x576.png)
Boost circuit Testing position
1. Left Terminals on SPD board
![](https://www.amosplanet.org/wp-content/uploads/2022/11/16696376831.png)
There are 4 terminals from positive , negative side of PV system on SPD board, you can test Each terminal with BUS+ like below:
![](https://www.amosplanet.org/wp-content/uploads/2022/11/16696388601-1024x573.png)
![](https://www.amosplanet.org/wp-content/uploads/2022/11/16696390411-1024x483.png)
![](https://www.amosplanet.org/wp-content/uploads/2022/11/16696390841-1024x576.png)
2. Right Terminals on SPD board
![](https://www.amosplanet.org/wp-content/uploads/2022/11/16696392271-1024x580.png)
There are 4 right terminals from positive , negative side of PV system on SPD board, you can test Each terminal with BUS+ like below:
![](https://www.amosplanet.org/wp-content/uploads/2022/11/16696403011-1024x577.png)
![](https://www.amosplanet.org/wp-content/uploads/2022/11/16696408061-1024x571.png)
![](https://www.amosplanet.org/wp-content/uploads/2022/11/16696408861-1024x532.png)
3. PV input Left Terminals on SPD board
![](https://www.amosplanet.org/wp-content/uploads/2022/11/16696411151-1024x473.png)
![](https://www.amosplanet.org/wp-content/uploads/2022/11/16696412921-1024x488.png)
![](https://www.amosplanet.org/wp-content/uploads/2022/11/企业微信截图_166968446955-1024x534.png)
4. PV input Right Terminals on SPD board
![](https://www.amosplanet.org/wp-content/uploads/2022/11/企业微信截图_1669684553343-1024x491.png)
![](https://www.amosplanet.org/wp-content/uploads/2022/11/企业微信截图_16696846214312-1024x486.png)
![](https://www.amosplanet.org/wp-content/uploads/2022/11/企业微信截图_1669684664255-1024x417.png)
dC-aC circuit Testing position
R phase upside IGBT
![](https://www.amosplanet.org/wp-content/uploads/2022/11/企业微信截图_16696853603023-1024x447.png)
S phase upside IGBT
![](https://www.amosplanet.org/wp-content/uploads/2022/11/企业微信截图_16696854157620-1024x367.png)
T phase upside IGBT
![](https://www.amosplanet.org/wp-content/uploads/2022/11/企业微信截图_16696854629656-1024x375.png)
R phase Downside IGBT
![](https://www.amosplanet.org/wp-content/uploads/2022/11/企业微信截图_16696855861606-1024x450.png)
S phase Downside IGBT
![](https://www.amosplanet.org/wp-content/uploads/2022/11/企业微信截图_16696856262331-1024x378.png)
T phase Downside IGBT
![](https://www.amosplanet.org/wp-content/uploads/2022/11/企业微信截图_16696856772296-1024x407.png)
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