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In Reply to: I just bought a B&K ST-140 for $4. I have a couple of questions about it. posted by The Reverend on April 10, 2007 at 11:36:12:
I will give you a couple suggestions. It is best to start unknown equipment with a variac. You plug the amp into it and then the variable voltage device into the wall. It allows you to slowly apply power to the amp. Before that, you could take the cover off and do a visual inspection of the inside. There are fuses on the power supply board and on the amp boards. Look for any discolored parts. Especially the output transistors. The blown fuse will tell you which channel to carefully inspect. You can replace any blown fuses and try turning the amp on. It does not need to be connected to anything other than power. If it is stable and does not blow more fuses. Take a volt meter and measure DC at the RCA inputs. This should be around .05 volt. This will get you started on checking the amp. Take your time and be careful.
Follow Ups:
OK, will do. I just need to get over to radioshack and at the very least get a voltmeter. I might wait on the variac until after I open it up and poke around. Thanks for the tips!
yes, you need a multimeter to check fuses and DC offset. I will venture a wild guess that the amp was so cheap because it has major problems. The output devices on the older models are available out of Great Britain. You can do a search at the tweaks asylum. Search all the way back to 1999. This amp was discussed heavily around that time. I highly recommend you limit your testing of interior components to the period before ever plugging the unit in. The two large filter caps can store enough energy to kill.
I am incredibly happy to say that your wild guess seems to be wrong for the time being! I set it up with some junk speakers and I am playing it right now. Seems to work perfectly!
Ok, well it has already been plugged in and powered up, and it started up with no fireworks or funny sounds. I will just open it up and look, not touch. Unless there are blown fuses. I would guess that you are correct, although I from what I can tell the people working at the thrift store had no clue what it was and did not test it because it had no power cord. Hopefully it works, but for $4, not much lost.
That was a very nice amp in its day and holds it own against some of today's amps. Smooth and reasonably powerful. You may wanna check audiogon or ebay for matching preamp(s) which were also pretty good.Great find! I love thrift stores.. I bought a set of Mizuno MP-29 irons (golf clubs) for $3 and sold them to a local used sporting goods store for $100 the same day. woo-hoo!
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