Studiomaster 2000e repair help

I'm bringing one of these back from dead and would appreciate some advice from anyone experienced in fixing them, as to whether a few substitutions would be viable please?

Both modules blew but one much worse than the other as it seems to have been previously repaired but without fusible resistors.

The first question is on the drivers for the HV/LV switching section, the original Rohm 2SB1186A/2SD1768A are out pf production and although a company in the US purports to have NOS, it will be expensive and I have been burned before. Can I therefore be fairly confident in using the MJ1503x type TO220 type driver as they seem fairly similar in terms of gain and Ft except that he MJ1503x seems more robust?

For the drivers for the main amplifier section, I think I have found newly manufactured parts from Profusion in the UK: 

http://https://www.profusionplc.com/parts/2sc4793lb-tf3t - http://https://www.profusionplc.com/parts/2sc4793lb-tf3t

http://https://www.profusionplc.com/parts/2sa1837l-tf3t - http://https://www.profusionplc.com/parts/2sa1837l-tf3t

I appreciate that using the original parts where possible is the safest approach but wonder if these too might not be substituted for MJ1503x parts, again on the basis that the latter is tougher, or does this role need the higher Ft. and lower Cob of the original part?

The last question is on replacing the output transistors, all of the MJ15003/4 from the switching section seem to have survived, all of the MJ15022/23s from the amp section have blown. If I have understood how class G amplifiers work correctly, this isn't altogether unexpected in the case of a short as the "inner" transistors do most of the shorting as the voltage drops but should I change them as a precaution? I am only asking as they are crazy expensive and like main filter capos, if i don't need to change them I'd rather not.

The 15022/23s I'm going to replace with MJ21195/6s as the seem cheaper and better specified than the latter but if I am to replace the 15003/4s, should I use these or go with still-available originals? 

Apologies for the lengthy post and thanks for your help.

The board was scorched in places but not burned through thankfully.

This is more of a labour of love than a commercial exercise, the bill for parts so far has come to 120 quid and that’s not including the main filter caps, which are reading a little low and should probably be replaced. 

Just so I’m clear then, the MJ1503x drivers can be used for both the amplifier and rail switching sections? 

Edit: the parts I linked to from Profusion are not NOS Toshiba but newly manufactured Unisonic parts?

http://www.utc-ic.com/upload/2011/1101/20111101111250426.pdf - http://www.utc-ic.com/uploadfile/2011/1101/20111101111250426.pdf

I’ve had this amp since day dot and it’s seen some partying, hence the sentimental attachment to it and the repair/restoration.

I’ve foolishly not taken a phot of the back of the amplifier bird and forgotten where the two little 470pF capacitors go, between the base and collector of the driver transistors? 

Mine doesn’t have those box film capacitors though. 

These are a bit of a bear to fix…

I’m not an expert by any means but enjoy getting stuck in.

I’ve got the module back in and it power up without any fault lights.

Matters of concern are around 1.5v of DC offset and the amplifier half of the module gets burning hot with no signal and no load.

I didn’t replace the differential input pair as they tested ok on a Peak DCA 75, I can’t see any other way to adjust the offset on this amp

And so was thinking of trying pairs of KSA992s to see if I can get the offset down.

The heating of the amplifier module is concerning though, I don’t seem to have oscillation as I monitor the output on the ‘scope, just the offset.

Any ideas chaps?