Stay away from??

[rca2000]

I'll try and explain this a bit more...others feel free to add more.

The aforementioned Sony sets with the "SG-613" GCS device (Gate controlled /turnoff switch), (occasionally an SG-264A was used) were VERY difficult to work on, because the GCS has ONE VERY bad attribute: it will SELF_DESTRUCT, if it loses gate drive--even if only for a BLINK of an eye !! Like an SCR,m they are turned on by a gate and STAY ON, until a reverse-pulse is applied to them. But, UNLIKE an SCR--a GCS can ALSO be turned OFF by that same gate---this makes them suitable for an amplifier ckt, at least a class C horizontal out ckt. Well.. "kind of suitable".


They, in reality, are NOT really suitable, because unlike a Bipolar transistor or even MOSFET or IGBT, they often fail in a horizontal ckt,. MUCH more than other devices, including tubes. Like a tube--when the drive is not there--they conduct "full-bore" , BUT UNLIKE a tube--they CANNOT handle this severe overload. Not even for a millisecond. Whereas all of use have seen an HOT "red-plate" because of even a slight loss of drive or such---we all KNOW they can "take it" for a short time, at least for awhile. Of course--this cannot be allowed to last--as it WILL kill the tube and more importantly its "load, meaning the flyback, in a short time if left this way. So, we go after the drive ckt, and fix it, and all is well. If, while chasing this problem down, there is a quick period of drive loss, we discover it, and correct it. if it last a few seconds or less--no harm is usually done.


BUT on a GCS horizontal ckt...ANY...and I mean ANY interruption or even reduction of the drive and ...BAM !! Out goes that GCS--WAY before you have time to discover why too !! They INSTANTLY short from "cathode" to "Anode", if that can really be considered the right terms for their elements. Think of all of the multitude of sets we have worked on over the years--with intermittent drive issues--usually, IF you catch and fix this in time-no harm is usually done, Sometimes, it may be a good idea to replace the H-out anyway, "just to be sure" all will be well, but often if you resolder the drive transformer of replace the cap in the base ckt--all will be well--for a long time.

But on these GCS Sonys---you get just ONE chance---to get EVERYTHING right--and I mean EVERYTHING !! Just a TINY problem with a glitch in the H-drive and BAM!! Out goes that GCS and fuse, and usually the B+ reg too and maybe more !! SO it was VERY difficult to fix one. Often, we would THINK we had one fixed, and POW !! Out it would go, ANd those Sony GCS'S were NOT cheap. Unlike Normal FET or Bipolar transistors, they did NOT get "cheaper" as time went on, either, and you could NOT use ANY other type than Sony !! If you id--you were SURE to be disappointed !! I fixed a FEW of these sets in years gone by--but do NOT really want to work on ANY more of them. By now--they are OLD, OVER 35 years I think--since Sony used them and I do NOT think ANY of the GCS sets would be fixable with all of those old caps. And Sony Trinitron tubes are NOT really known for their long-life, anyway...

So...STAY AWAY from Sony sets made from about 1973-1978 or so...unless you are a SEVERE masochist !! Maybe THIS will make things more clear for you all.