Leslie wrote:

Wow, following this discussion with much interest guys!

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StuckE30 wrote:

I assume the transistors need to be removed from the PCB to test across the leads. I don't know what to test for, and / or if the test can be done with a DMM or if I need equipment I don't have.

Good link Søren. Our comrade here will have to learn the hard way by himself! But then motivation is everything!

I prefer to use the diode position, however.

I suggest our friend here should nonetheless get a nice book about the basics. However, nothing will replace a good teacher... like you Søren!

I have no merit, I learned at school. 😎

StuckE30 wrote:

OK so please correct me if I'm wrong but TR25-27 (SC3281) and TR30-32 (SA1302) are the output transistors? Initial investigation looks like both of those transistors are NLA from Toshiba and difficult to source unless you want the cheap Chinese knockoffs. (I don't)

They are discontinued but have been replaced by new versions (and new numbers). I can dig out what they are if necessary, but you should be able to google it. The new ones are readily available.

/  Johan

chartz wrote:

I have no merit, I learned at school

I learned at school too, but mechanics 😁, the electronics I had to learn the hard way, that why I only passed the link, just as a reminder, I found all the theory and basics, I have needed until now, on the internet. And I hope StuckE30 will follow the hint.

I started out with a BM 901, and after reading about it on this forum, I got the impression, that it was easy, just change a couple of caps, clean a little, and done. Well not so, the next one was a BM 2400, before I even started on that one, I decided that every time I changed or run into something I didnt know, I would look it up, like a diode, what is it, why is it there, and for what. And as a result the BM 2400 took 3 weeks of and on, before it was working. (Martin would have done it in a couple of hours). And even so I had to get help from the forum. 90 % of the time for the BM 2400 was spend on the internet. I still need a lot of help, but now at least I understand what the experts, like you Jacques, are talking about.

So StunckE30, dont give up, but start reading, there are no fast way to do it, only the right one.

I haven't had any luck finding a superseded part of the transistors via google. Just a pile of links to Chinese junk knockoffs.

While Google and the internet in general is a great resource sometimes seeking sage advice from an individual familiar with the exact product you're working on, more so familiar with the common failure modes of its components is infinitely more valuable.

Where I'm sitting it seems prudent to replace all 8 transistors that are attached to the main heatsink body... but would that even fix it? I don't know.

What about all the smaller free standing transistors on the PCB? I wouldn't *think* them the problem based solely on my understanding that they aren't handling the kind of current that can ignite a resistor like TR25-32. Again perhaps my understanding is wrong. Just thinking outloud.

From my rudimentary understanding of the diagrams in the service manual I have it it seems reasonable (to me) the problem would be in TR24/TR29 or TR25/TR30 as the emitter resistors on TR25/30 are the ones going up in smoke. That, or somewhere up stream from there.

I may be able to find the time this weekend to remove the transistors and check them out with a DMM, it looks exceedingly simple, its just the time/labor involved.

Hi , im would like to restore my crossovers , but i don't know what part to order as i don't have any schematics for them.  I have uploaded picture of crossover boards on my profile. Thanks a lot for you help 

Try to contact Beobuddy, member and Penta expert...

Ok thanks:)