Pioneer SX-253R questions,advice please

[audio80]

Hi everyone, Im new to the forum and need some advice from the pros. I have this 90s pioneer receiver that I'm going to service,th big output caps are really swollen at the top and ready to go. Looking over the schematics I noticed the SX 253R and the SX 303R are nearly identical,the main difference is the 253r is 70 WPC and the 303R is 100WPC. I want to replace the 253Rs transistors and caps to the ones used in the 303R to upgrade its power to 100wpc instead of 70wpc.what else would I have to replace in the receiver to accept the new load? I imagine I would have to re bias,but have no scope to do so. Would I need the transformer from the 303R as well? so I basically want to do this

SX253R Q1,Q2 from 2SC4689 to SX303R Q1,Q2 2SC3281
SX253R Q3,Q4 from 2SA1804 to SX303R Q3,Q4 2SA1302
SX253R cap 701&702 from ACH1044 8200uf 63v to SX303R ACH1204 8200uf 71v

Is this doable or just a bad idea in general?

 

[petehall347]

maybe have to change mains transformer for higher voltage one.

 

[OMGCat!]

You'll have to check the rail voltages as beefing up the transistors won't change the output power by itself. Like petehall says, they likely ran a higher voltage transformer to accomplish this.
If the caps are swollen on top make sure that it's not just the plastic covers that lots of large e-caps have. They tend to go convex after years but the metal of the cap itself is flat.

 

[elnaldo]

I agree. The power comes from the power supply. With the same power supply your amp will output the same 70 watt regardless of the output transistors. Anyway I don't think those " extra" watts worth the effort. Not a big difference from 70 to 100 Watt in terms of how loud your amp will sound with the same speakers.

 

[audio80]

thanks for the feedback guys,Ill replace the parts within spec.