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Old 12th Mar 2017, 10:00 am   #8
Skywave
Rest in Peace
 
Join Date: Jun 2006
Location: Chard, South Somerset, UK.
Posts: 7,457
Arrow Re: Dropping mains voltage to mains transformer approx 20V

The above suggestions incorporating an external transformer are sensible and will solve the problem. One possible snag to them is that the additional transformer will be external to the item, which apart from a 'clumsiness' aspect also includes the possibility of it accidentally not being used or even lost / mislaid. That can be avoided, of course, by a 'hard-wiring' style, but that brings us back to the 'clumsiness' aspect.
Is it possible to re-engineer the item by the addition of a heat-sink at the rear of the case and to relocate the series-pass transistors to that sink?

Another alternative is to broaden your view of this and consider your mains supply voltage: you stated 248 v. That figure causes me to wonder about the rest of the equipment you have there - running on that voltage. Perhaps a suitably-sized transformer is called for, to reduce the mains supply to a nominal 230-v. for all of that equipment? It might be an opportune moment to consider the fitment of an isolating transformer.

Al.
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