110v to 240v conversion for av754 and tfm25

Hi, I am trying to convert a tfm 25 and an av753 from 110v to 240v. I could use a step down transformer, but the transformers housed within the carvers may have the windings (there's a tfm 25 service manual that lists "voltage conversion" as a topic). Question: Does anyone know of a procedure to do this - or does someone know that internal changes can not be done and that step down transformers have to be used?) Thanks for any insights!

I have notes somewhere around here for the TFM amps. I will start looking. It has been a while since I did a conversion.

Thanks for looking! I've found the page in the service manual for the tfm25 - the procedure seems simple, I'll give it a shot. Next the AV753 - I have not seen a service manual for it yet, nor have I seen a 220V version of it. Still more research to be done on the AV753.