infocus projectors - pulsing pictures on region 1 discs

Can anyone help with this mystifying problem?
Originally used an Infocus X-1 with Denon 2900 DVD which is multiregion.
Since moving to a new address, I've found that the picture pulses when playing region 1 discs only when the Economy 10 off peak electricity kicks in.
Sent the projector away for repair- no fault found.
Upgraded to Infocus LS110, same problem!
Region 2 discs play fine at all times.
Points to an electricity supply problem- but region 1 discs play fine using the same DVD player through a Sharp Aquos television.
Help!