As these early sets age so the parts become more and more scarce, some parts more than others. The following article details how to go about converting the CTV25 valve derived EHT generation to Tripler, should the original 25kV over-wind fail. This has the added bonus of removing the lethal X-Rays generated by the Shunt stabiliser and although it can be argued the sets originality is compromised, I would suggest that at least the set can be made to function once again.
I have a CTV25 in my collection at one point in its life it had been converted to tripler, luckily a NOS LOPT was acquired and the set returned to original specification and yes it generates the X-rays but these are contained in a shielded cage. Remember to never operate the set with the cage removed. As a further note I have a G6 which also at some point had a tripler conversion but has also now been returned to original spec.Updating-Decca-CTV25-with-a-Tripler-Tel-Mar-1982