Use manual override and see if lights work correctly.
Check that bulbs are each working. If one bulb is burned out, then others will burn out, and the load change can cause power pack to stop functioning.
Always unplug power pack when working on lights.
Power packs do not have repair parts anywhere on the internet that I know.
I checked Intermatic, Malibulights, ebay, amazon, and listened to fixya customers.
Occasionally folks take power pack apart, but nobody reports being able to repair the transformer or timer.
Once power pack goes bad, then it needs to be replaced. Bad news because they're expensive.
'Harry' wrote to fixya with some information.
His timer stopped working so he bought cheap plug-in timer, set power pack to override, and then plugged power pack into cheap timer.
Harry also said his power pack has 5 year warranty and he was negotiating with Malibulights.com for replacement. No word how that came out.
Best I found are tips for next power pack that might save money:
The reason I add tips now, before your power pack needs replacement is some fella wrote fixya.
He bought 500 Watt power pack to replace 300 Watt > thinking bigger was better.
Power pack burned out. Here's why:
a) Match wattage of bulbs with wattage of power pack
Lets say you have fifteen 20 watt bulbs = 300 watts, so install 300Watt power pack
b) Installing a 500W power pack on 300W of bulbs will burn out bulbs and power pack.
c) Replace bulbs as soon as they burn out or other bulbs will burn out and power pack will burn out.
d) When working on bulbs, unplug power pack or it may burn out.http://www.malibulights.com/guides_support/low_voltage_planning_guide/select_your_power_pack
Add a comment for more free help.
Also take advantage of fixya phone service.
For a price, expert speaks with you over phone while you work on timer or any do-it-yourself project.
Fixya is always less expensive than a service call.