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Hello all,Today I was poking around at the local thrift store, flipping through montovani and johnny mathis records, etc. As I was walking out the door I decided to scour the store one more time. There is an electronics section but it is usually all plastic stuff, so I don't pay much attention. However, I was looking and I noticed a big black box that looked like a power amp. I looked more carefully, and it was a B&K ST-140, and it was only $4. I just decided to buy it, it is in perfect cosmetic condition but untested. It has black handles, and from what I learned online apparently that dates it somehow (though to when I am not sure).
Here are my questions:
1. I have never used a power amp before. Can someone explain to me how I might hook this thing up to test it out?
2. Since it has no power cable, will any old power cable do? Should I just by a blue jeans cable or something?
3. The fuse for the right speaker is blown. I am nervous about this, since I don't want to mess up my new Wharfedale 9.2's. If I replace the fuse and test it out with my system, is there any risk? Also, could this be indicative of some other sort of problem?
4. Does anyone know anything about this behemoth? I basically bought it because it looked new, was heavy, and said made in the USA on it.
5. How should I test it? I did connect a power cable from my guitar amp and flip the switch. It didn't catch fire or smoke, and the light came on. Good sign so far?
I appreciate all of your help!
Thanks,
Follow Ups:
Wow! I am pretty surprised. I am just going to let it run for a while to see what it does before putting it into my system. One question: It seems like when I start it up, it makes quite a thump. Any reason for concern, or is this sort of thing normal?Thanks,
It has a relay the kicks in and when it does it thumps the speakers a bit. It hasn't hurt my speakers so far. Nice warm sounding amp but a tad flabby in the bass.
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...very well regarded amp. If you do decide to power it up, I'd use a pair of speakers that you don't care much about as a first test. Also, I would check the fuses closely; even if there are fuses in the fuse holders they might not be the right size.Reminds me of the time I saw a very dusty grey box in a pile of stuff at a thrift. It was an H/K 450 DC in perfect condition; a real sweet music maker.
How would I find out if the fuses are correctly rated? I am honestly assuming that they are, at 4A, 250V. The one in the left channel is there and intact. What would cause a fuse to blow in this situation?
...the amp is working fine; which is great. Usually the fuse rating is marked someplace by or on the fuse holder, or on a tag on the back or bottom of the amp (I've also seen it inside the case, sometimes on a small schematic). If the fuse in place is of a higher rating than it should be, the amp will not be adeqautely protected. If the fuse in place is of a smaller rating than it should be, the fuse will be more likely to blow. An old fuse of the right size can also get worn out from stress and blow. A visual inspection does not always reveal a faulty fuse.If everything is working well, with a good cleaning of deoxit, a touch of progold, and some good wires, you should have a sweet and well regarded amp (for $4 ; ) What are you using as a pre?
I am using an NAD 7000 for the pre.Believe it or not, the connections are totally clean. I don't have any deoxit, but heck, I could go get some.
I am thinking that I will just pick up some blue-jeans cables to connect the pre, but I don't know what power cable to buy for it. I don't want to break the bank on cables, I just want to hook it up and give my guitar amp's cable back to it.
I can't believe someone would get rid of something like this! If the only problem was a blown fuse, well, wow, I just bought an amp for $4.50!
...an integrated amp with pre-outs.
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.
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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