Is there anywhere a list of generic transistor/darlington for AF push pull output stages from eg 10 W to 100 W in the different configurations. I have to repair some amplifier but do not find the old powertransistor. Idem for the drivers.
On Internet I can find some information (Eliot, Sams, wiki...) but no global ones.
It would depend on the vintage, design, general ruggedness and much more. I deally, you will find a schematic for the item you intend to repair, and re place accordingly. There are more than a few options.
A very common power transistor is the 2N3055. Which in most devices may be replaced with the more rugged 2N3772, possibly requiring some attention to the bias settings. I have five devices from three different manufacturers, Euro and US that use the 3055, most of which have been replaced with the 37
72, one of which needed bias adjustment (could have been left alone with a small increase in measurable distortion).
That is ONE, and only ONE example. And all of these amps used NPN outputs i n PP. Many use NPN/PNP configurations.
My advice would be to look at the OEM transistor(s), and then look up *that
part and find out what options may be available. If you are going to make a habit of this, invest in a tester that will allow you to match parts. It is often not entirely necessary, but I have found it makes for better resu lts as transistors do not drift as much as tubes as they age.
Ideally, you will find a schematic for the item you intend to repair, and replace accordingly. There are more than a few options.
e replaced with the more rugged 2N3772, possibly requiring some attention t o the bias settings. I have five devices from three different manufacturers , Euro and US that use the 3055, most of which have been replaced with the
3772, one of which needed bias adjustment (could have been left alone with a small increase in measurable distortion).
in PP. Many use NPN/PNP configurations.
at* part and find out what options may be available. If you are going to ma ke a habit of this, invest in a tester that will allow you to match parts. It is often not entirely necessary, but I have found it makes for better re sults as transistors do not drift as much as tubes as they age.
p.s.: If a gun were put to my head and I were forced to make some *generic* suggestions, they would be:
a) A small stock of 2N3055 b) A small stock of 2N3772 c) A small stock of TIP31 (NPN driver) d) A small stock of TIP32 (PNP driver) e) A small stock of 2N3054 (NPN driver)
That pretty much covers a range of 70s/80s equipment from Revox to Dynaco t o AR and even a very few B&O units. But it is a tiny range in a vast field.
I have 2 amplifier to be repaired : the first one a scott a416 (i have the schematics but in bad quality and with drawing errors). The second one is a Marantz superscope MS-30 (without schematic)
I'd be surprised if the MS-30 had output transistors. These multichannel all-in-one one units often just used a power IC for each channel.
Sounds like you don't know if the output circuit is the actual problem, here, or you'd be able to quote the part number from its physical markings, on the assembly.
Thanks for the answers. The MS-30 has a push pull stage with pair of transistors with their bias mounted on the cooler. But I do not have the schematic. The problem is distorsion in the left channel.
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