Thanks for the comments. A subscriber has kindly contacted me and recommended the larger Harbor Freight machine. He has been using this model for a year now and runs it at 2 x 480 seconds with an hour interval between. Dick did mention that he'd had two smaller models burn out prior to this. The last model I bought was a James 2200m (professional) with the transducer welded to the underside of the tank. The timer had a maximum run time of 60 mins, I only ran it for just over 15 mins. So with those machines it must either be the consistency of the lecithin mixture, or the fact that there's nothing in the tank. I did get to speak with James of James Products and he didn't seem to think there would be a problem running them in this way and assured me that they sell thousands world wide with no problems. Thanks for the advice about looking on Ebay, there's a couple I've added to my watch list, but if the model Dick recommends is available here and I think I've found the same model on Amazon.co.uk, I'll go for that as it's also a bit of a bargain at £30!
Thanks again! Richard
