Troubleshooting SMA Technologie AG
68 SB40TL_50TL-IEN081211 Installation Guide
12.2 Checking the Varistors
If the Sunny Boy shows event number "74", one of the varistors is probably defective.
Varistors are wearing parts. Their functioning diminishes with age or due to repeated responses as
a result of overvoltages. It is therefore possible that one of the thermally monitored varistors has lost
its protective function.
Check the varistors as described below:
1. Open the Sunny Boy as described in section 8.1 „Opening the Sunny Boy” (Page 49).
2.
3. Loosen the screws on the upper lid.
4. Pull the lid forwards at the bottom edge.
5. Push the lid upwards and remove it.
DANGER!
Lethal danger caused by high voltages in the Sunny Boy!
• Wait five minutes before opening the upper lid, so that the capacitors can
discharge!
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