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Deleted member 537430
I’m fooling around with an old 303 and wanted to know specifically about hFE ratinings of the TR104 on the driver board and TR200 on the power supply. Both of these were part # U17229 back in the day. I found the ZTX504 in both positions on my amp. I’m going to replace them with something more modern and DADA recommends the BC556B for both locations. At one time they recommended the BC556 in the power supply section and BC556B in the driver stage. Not sure why the change, other than the fact that the BC556 is/was hard to find.
Anyhow, here are some numbers to ponder:
hFE
ZTX504 50-300
BC556 110-800
BC556A 110-220
BC556B 200-450
What would you use, and where? I have both the A and B.
Thanks
Anyhow, here are some numbers to ponder:
hFE
ZTX504 50-300
BC556 110-800
BC556A 110-220
BC556B 200-450
What would you use, and where? I have both the A and B.
Thanks
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Not sure I would use BC556/A/B. It's rated at 65V BVceo which is very tight for a 67V supply. Vcbo is 80V and in a Class B driver position it may be possible, but I would recommend a higher voltage transistor, perhaps 2N5401 but the pin-out means rotating 180 degrees to the BC556x. Gain 60-240 @ 10mA. And the 2N5551 for the NPN.
You don't need to worry about hFE. This is part of a triple whose gain is around half a million.
I've used BC556 many times with no problems.
I've used BC556 many times with no problems.