On Tue, Aug 21, 2012, at 09:47 AM, Justin Richards wrote:
> As a novice, finding replacement transistors for the amp section that
> are pin compatible, cheap and readily available has proved to be time
> consuming.
>=20
> Currently a 2SD314 NPN (T220) is in the output stage.  TIP31C(T220)
> appears similar , as is 2N3055 (T03) and the circuit board has been
> designed to take either T220 or T03.
>=20
> min/max hfe for  2SD314 and 2N3055 are 40/320  and 20/70 respectively.
>=20
> As amp designers must consider a range of hfe's anyway and as I have a
> handful of these (both TIP31C and 2N3055) it seem like the right
> decision.  (I intend to change the other side PNP to it its complement
> MJ2955 and similarly in the other channel)

Either choice is likely to be OK. But the 2N3055 is a lot tougher. If
you are running 4 ohm loads it would be a better choice, especially if
your amplifier has higher than 50 volts total supply voltage (+-25
volts). Or if you expect it to handle the occasional short circuit.

On the other hand, finding non-counterfeit transistors in TO3 packages
is getting harder, so you might have a TIP31A or worse inside the 2N3055
package. In which case using a TIP31C would be a better choice :(

Best regards,

Bob

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