[Alastair E]

Ah--The Sony GTO Line-timebase silicon switch 'Orrible bloody things!!.....

In UK, we had rather an infamous Sony model, the KV1810UB and KV1810 MkII.--Actually quite a compact neat set with great performance if the CRT was good

Both these sets used a SG-613 GTO in both the PSU stage and the horiz out. A Dry-Joint or failure of 19V rail would kill the horiz out GTO--the short then on the +B line would kill the PSU one...

These SG-613 were around £15 Each here, and a normal horiz-out transistor like a BU208 or BU508A maybe £1-2 at the time, so £30 in parts before you even started on one of these 1810's, Plus the so-called, 'Kit' of other crap you needed to change according to Sony, as a reliability measure--That didn't cure the blowing SG issues....

Wasn't long before a bright spark came up with a way to use a standard Horiz O/P Bipolar Transistor in place of both the PSU and Horiz-Out GTO's....

Involved changing the Drive Transformer for a type used with Horiz-Output Transistor, and deleting the original GTO drive circuit.
A BU508A was used quite successfully to sub the SG GTO with the alterations to drive it right by replacing the drive transformer by me for a number of these repairs, and was a good reliable conversion.
On a few of the earlier conversions, I retained the SG in the PSU (as I had sill a few around) and just modded the horiz-out stage. I kept one of those early ones for may years and no further trouble from it.