HiFi-Do E-mail Newsletter

Hello, Nice to talk you! I am Ito, a new recruit, working at the service department for Ohsu Main Store since this March. I would like to answer your questions regarding audio equipment repairs as simple as possible so that you can understand easily. For my first report on the e-mail magazine, I would like to introduce my work area.

Take a look at these two pictures. The object in the left picture is an oscilloscope, but what do you think it is in the right picture? The answer is an oscillator! You may feed me saying "Yeah, Right. Who doesn't know?" But I didn't know what it was when I first saw this picture. Anyway let me explain about this oscilloscope a little bit. Checking the state of waveform on the oscilloscope monitor enables you to know if the audio equipment is in a good state or not. But you need to first connect the oscilloscope (in the left picture), the oscillator (in the right picture) and audio equipments with each other. Then the sound from the oscillator is received by a power amp or pre amp etc., and then the amplified sound through the circuit is received by an oscilloscope which reflects it on its monitor in the waveform. You need to find a locating fault(s) by checking the state of this waveform. But since this work is very difficult, you need to have various knowledge and experiences. And I would like you to focus on two connectors connected to the oscilloscope. These connectors are called "Probe" and to be connected to the output terminal of a power amp. How much do you think this Probe costs? Don't get freaked out. It costs 5,230 yen!! Holy cow! Sure is expensive! Then how much will an oscilloscope actually cost???

Here are another two pictures. I decided to look at the waveform for real. The one in the left picture is recently repaired DENON "PMA-780D" pre main amp. You don't want to miss out on buying this if you see it in our store. (lol) The waveform in the right picture is from the oscilloscope to which 1 kilohertz sign wave from the oscillator is connected with no-load through this pre main amp. It is beautiful sign wave with no distortion. Then I checked this state by actually making a sound. I could hear the continuous hollow sound like "Pohhhhh" at this state of 1 kilohertz sign wave. I also checked this state by putting a CD on. Frankly speaking, the sound was softer than I thought and I felt the sound comes to the front, which made me want to buy this pre main amp.

Here are an analog (in the right picture) and a digital (in the left picture) tester. These are indispensable items for repairs. We use the analog tester to check transistors, condensers and so on. And we use the digital tester for the power voltage/volt-ohm check and for the amp DC leak check. I always break into a cold sweat when using these testers.

Finally I would like to explain about these two pictures. The hair dryer-like object in the left picture is indispensable for quieting the noises resulted from a bad contact by recovering the contact. I really appreciate this since it quiets the noises very well. And a soldering iron! I burn my hand often with these. Objects in the right picture are a work table and the equipments in order, which I introduced this time.
I simply explained about my work area and works at the service department. For the next time, I would like to give you an in-depth explanation about the product structure, mechanism and so on. Thank you very much for your subscription and I hope you will enjoy my reports from now on.

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