What is affected if the hFE rank of the replacement transistors is too small? Sound power in watts? Sensitivity? Idle power consumption? Noise?

I accidentally ordered a hfe rank of 50-100 while the originals are apparently in the 70-140 rank.

 

Base current.
If you treat a bipolar transistor as a voltage-controlled device. Collector current varies with the exponential of base voltage.
hfe tells you how much base current will flow as a fraction of the collecor current.
More base current means that the stage will have a lower input impedance and draw more current from the previous stage.

 

Distortion?
Maybe especially if it's part of a complementary pair.

But as the two selections overlap, you may be lucky.

 

Is this for an audio amplifier? It really depends on where and how it’s being used. It may or may not matter. 50-100 is tighter than 70-140.

 

Is this for an audio amplifier? It really depends on where and how it’s being used. It may or may not matter. 50-100 is tighter than 70-140.

If it’s part of a long-tailed pair, replace both.
but 50-100 isn’t tighter than 70-140, they are both the same. Both +/-40% from the centre value which is 71 or 99.

If you can measure any changes to the amplifier, the you must also be able to measure HFe.

 

Is this for an audio amplifier? It really depends on where and how it’s being used. It may or may not matter. 50-100 is tighter than 70-140.

Yes, it is Sony TA-F530ES.
https://www.hifiengine.com/manual_library/sony/ta-f530es.shtml

https://www.semicon.sanken-ele.co.jp/sk_content/2sa1215_ds_en.pdf
https://www.semicon.sanken-ele.co.jp/sk_content/2sc2921_ds_en.pdf

Both for L+R channels ordered. I just measured the old ones with multimeter, hFE is about 110-115.

 

I found the schematics. I would try it, they are the output transistors, it may produce some distortion (THD) at higher output but there’s usually some room for variations. I would match vbe and beta as close as practical, it’s not as touchy as the front end differential.

also there’s an even higher category Y which are 90-180

 

A good designer would have designed it for hfe=70, so you would probably count yourself unlucky if the new ones were less than that.
It‘s doubtful that it would affect the bias and thus the distortion, but you could trim that with RT351 (which you should do anyway after changing the output transistors). The only thing which could be affected is the maximum output power Into the minimum impedance load.

 

Dependence upon highly variable factors such as HFE very small in a well-designed product and the difference you describe is in itself very small. Reasons for having designs largely independent of such factors is product performance consistency, which relates to production yield of the finished product and reliability.

 

Thanks for the answers. I will measure them when they arrived, hopefully hFE is about 70-80. If it so, I will solder them on...unless they are fakes. The genuine weighs about 18.4g.

https://www.diyaudio.com/forums/solid-state/229044-2sa1215-2sc2921-identify-genuine-fake.html

 

New Sankens arrived. Weight is ok about 18,6g, case looks genuine, but these are sanded and painted. I was able to remove paint and markings with acetone. Genuine markings is not possible remove with acetone.

hFE values are good 17,118, 120, accidentally very close of my originals, except one wich have 159.

How I can be sure, what models these really are? There is many models whit this MT-200 case with similar hFE ranks.

https://www.semicon.sanken-ele.co.jp/sk_content/2sa1216_ds_en.pdf
https://www.semicon.sanken-ele.co.jp/sk_content/2sa1295_ds_en.pdf
https://www.semicon.sanken-ele.co.jp/sk_content/2sa1493_ds_en.pdf
https://www.semicon.sanken-ele.co.jp/sk_content/2sa1494_ds_en.pdf

 

Now I have mysterious idling adjustment problem in the right channel. Standard idling is 7mV.

- Idling adjust pot clock at 10-11 I can reach 8-9mV, on minimum it rises to 9-11mV

- If I put audio volume knob to 11, I can set it to 7mV and under, also If I put mute switch on -20dB.
So in practice power consumption is about 45W volume knob at 0, and at 11 consumption drops to 35W!

I swapped left and right channel power transistors, and problem still exist. Before repairing C356 was exploded and R355 burned. Amplifier sounds good, components looks good, no hiss or hum, but something is wrong. Resistor, capacitor, diode…?

 

Check DC offsets and for instability on the output. (By the way, I can't find C356 on the digram)

 

err C359

 

Offset shows minus: left -1,5mW right -2,5mW. Same on B-terminals.