Possible issues in replacing bjts with more powerful parts

[dreamth]

if there's no pot there you need to look at the resistor divider values but that is only if the 0.47ohm resistors get you in class b region at high power.Usually there's not a really big problem with that.As you saw in the first pic here:
https://www.diyaudio.com/forums/eve...sues-replacing-bjts-powerful.html#post6341861
they are using 0.47ohm resistors in a 120w /channel very fast amp too.
Of course you need to replace all transistors not just two in four per channel.

 

[ginetto61]

Yes, i replaced all the components with much better and faster transistors and some better capacitors in that final stage after that severe burn ....

very impressive stuff indeed. A little crowded maybe ? the only thing i have done in the past aside destroying a little Rotel integrated is recapping an old Nikko Alpha II ... another interesting power amp
I buought it at an audio fair and one channel was behaving badly After opening it i discovered that they had repaired it putting wrong drivers (exchanging npn with an pnp)
Restoring old units is a work of love ... needs time and patience and competence

 

[dreamth]

The DLD stage itself is wired that way...

sorry for disinformation...the dld is on the pcb, the drivers are the normal common emitter transistors

 

[dreamth]

very impressive stuff indeed. A little crowded maybe ? the only thing i have done in the past aside destroying a little Rotel integrated is recapping an old Nikko Alpha II ... another interesting power amp
I buought it at an audio fair and one channel was behaving badly After opening it i discovered that they had repaired it putting wrong drivers (exchanging npn with an pnp)
Restoring old units is a work of love ... needs time and patience and competence

yes it was really crowded, but the original pcb had no heatsink for the drivers and current mirrors .The current mirrors didn't really needed any heatsink but at the time i was just making everything bigger not being able to fully understand much of what i was doing What was really good in my life was that i never screwed it too bad withmy trials...i think i was lucky to make some sucessful things withouht fully understanding how they work, but i took extreme precausions every time i was working on something.

 

[ginetto61]

Hi ! i think that it would be much more productive to wait for the pics ... i will look closer on the pcb. This amp will be my guinea pig ... i would like to see if the big Toshibas will fit in ... i love Sanken multiemitter ... those would be a dream I am aware of a lot of high end power amps using just one pair of those little soaps Let me have some days .... i will post back with pics
Thank you very much again and have a nice day