NONE of the original transistors are being made today. Over the years a few techs here have researched, tested on their own gear, and put out lists for Most of the PIONEER SX (and SA, etc) series units. Mark the Fixer being the most prolific and tested. His lists have been used for almost 25 years to my knowledge.
NTE are absolutely the last junk you'd want to put in your SX-636. Go up to the lists in posts #3 and you'll find the replacement parts needed. If it's NOT LISTED it's not a problem part. All parts on this list are proven, and are direct from FAIRCHILD / ONSEMI, NICHICON, WIMA, CORNELL-DUBLIER ETC. They aren't from the "lowest bidder" like NTE gets their stuff and you don't know where it came from. Stay away from NTE unless it's the last thing in the world and you are absolutely unequivocally desperate!!! Besides, the Fairchild Transistors are generally less expensive than the over charged NTE's and a hell of a lot better product than the NTE stuff.
The two transistors you want to replace NOW are ALL of the 2SA725/726. These are on the 10 worst transistors list. Have your tech go to Mouser and order KSA992FTA, FBU, FATA, or FBTA. The "F" is the Gain rating. The rest of the suffix is the packaging and has no bearing on the transistor itself. Bulk, tape, etc.
The other and more important replacement is the 2sc1451. It's replacement is the KSC3503DS or DSTU. Again the Suffix is broke down to the "D" being the gain rating and the rest is packaging . Just get the cheaper of the two.
Don't worry about the other two as they aren't problem children. Replacing the 2sa725/726 and the 2sc1451's will mitigate 90% of the noise problems in the 636 short of recapping.
Personally it sounds to me as if your "TECH" is fabricating excuses for NOT wanting to work on this unit. Recapping and restorations are loss leader's for shops. Their "bread and butter" is fast turn around items that bring in $$$. Restorations take time and $$ from the average shop. FIND ANOTHER SHOP that will do RESTORATIONS. OR Ask around on the FORUMS for Someone on AK that will do a restoration and do it correctly with all the parts that have been researched, tested, and proven out on hundreds if not thousands of units over the years. And we CAN and DO update these IF a member puts up a list to be vetted. It will be researched against what Mouser has, obsolete and discontinued parts updated, etc., so you have the latest parts list with parts that will do the job and are rated for a more powerful unit (to mitigate against a over-voltage or running a part at the ragged edge).
You will more than likely have to ship the unit out. But it can be packed so no damage is done. And you'll get back a unit that has been brought up to 2017/2018 spec and better than what PIONEER designed in some respects. A shop ain't gonna do this as they'll lose $$$ on it.
Larry
