At 70V 2.5 ohms you have a nearly 2000 watt load, which is not acceptable for 12-15 speakers nor the TPU100B. Did you check with a DMM in resistance mode or with a proper impedance bridge such as a TOA ZM-104?
You can also check for ground faults by measuring with a DMM between earth and each leg of the speaker wire.
Bogen is still in business so you can contact them for repair or a new part once you verify with the proper tool whether or not you have an overload.
https://www.bogen.com/
