Proton AM-30: Blown 2SA1302-2SC3281

[echopapa]

Hello everybody. This is my first post in diyAudio.

I have an AM-30 Proton amplifier which one channel blown. One output transistor (2SC3281) and both drivers are visibly burnt, BC546 thermal compensation shorted as well.

Looking at the output transistors (see pict below) I am wondering if they could be conterfeit. Only one of them has clear marking, all are black not green...

Also, since I don't have the schematics and couldn't find it on the internet I need help to replace the drivers: I can only read D669 on one (BD669? can't find any information on that!) and maybe BC... on the other. Any idea?

Thanks in advance for your help!

Laurent

[jackand08]

Hi there,

The transistors that you suspect to be counterfeit may well be genuine transistors but from different batches or made in different fabrication plants. When you order in future, it is best ordering from a major supplier as the devices are less likely to be counterfeit.

Regarding the blown driver transistor, this is a Hitachi device and is a 2SD669. You may have to order an equivalent to replace it as they may be hard to get hold of.

Also, even after you have replaced all the parts, it is worth checking for other problems too before powering up the amp, as these problems may show themselves and undo all of your hard work and money spent replacing the devices.

[echopapa]

Jack,

You put me on the track: 2SD669 and its colleague 2SB649. Thanks!

Laurent.