7/24/2023 0 Comments Shelp over audio tuner![]() ![]() As soon as the note on the tuner turns green, you can be calm, the string sounds right □! If the tuner shows a deflection, twist the peg, try to change the sound of the string. Play any string - the chromatic guitar tuner will show what note it is, and how accurately it is tuned. So the online tuner will have the opportunity to hear the sounds of your guitar. Your device will ask for permission to record sound from a microphone - allow recording ⏺. This will be close enough to the maker's specification for most models to obtain good performance along with reliable operation.Press the "Turn on" button under the tuner. After this, adjust the offset for zero volts (or half the rail voltage for single-supply designs) at the midpoint and repeat the process for the other channel. Adjust the bias control for 10mV, then re-check (and reset if necessary) after ten minutes. With the speakers disconnected, connect a voltmeter across one of the emitter resistors of the output transistors. In the absence of the maker's data the following procedure can be used. These are fine adjustments that will tend to drift with age and so it is always worth checking that they are correct. ![]() ![]() Many amplifiers have pre-set controls for output stage bias and offset balance. Source or monitor switches that are noisy, dirty protection relay contacts and missing pre/power amp links cause many amplifier malfunctions, so check the simple things like these, first. With transistor amplifiers, never connect the loudspeakers until you are sure the output stage is sound, eg, there isn't a substantial DC voltage present at the loudspeaker terminals.Įarly MOSFETS are used in the output stage of Hitachi’s HA-7700 power amp Blown fuses almost always mean output transistor trouble so check them for shorts before replacing the fuses or applying power. The key components in any amplifier are the output transistors, be they discrete or in a chip. That being said, you will soon learn to identify which components are often defective, and be able to make a bee-line for them once they are spotted. This rarely solves the problem and can introduce many more if the replacements are the wrong type or fitted incorrectly. There is currently a fad for replacing every electrolytic capacitor in sight, regardless of the fault. This approach is sometimes necessary in older models but it makes every repair tedious, expensive and one learns nothing from it. Mint examples would be an extravagance at this stage, but it is worth seeking out pieces that are at least complete and not obviously the result of someone else's failed repair or upgrade attempts.Īn advantage of equipment of this era is that as a rule it does not require the blanket replacement of components to restore original performance. It is ubiquitous, generally safe and solid, free of designed-in faults and quirks and normally has comprehensive service data available for it.Ī library of service sheets used to be jealously guarded by any workshop that had the resources to amass it, but now full manuals can be downloaded from a number of sources, usually free of charge.Ĭondition is another factor to consider. ![]() In choosing what to buy (or allow yourself to be given, because a lot of this stuff is free) I would recommend starting with Japanese and Continental components from the mid '70s to the mid '80s. The world is full of broken hi-fi kit and there's plenty to hone your skills on. Don't make your first mistakes on equipment that is valuable, either in sentimental or financial terms. The next step is to choose what you are going to practice on. There are simply no shortcuts in this preparation and you will get nowhere without it. You'll also need a full understanding of the potential dangers of mains-powered equipment and how to use your tools safely and effectively. The ability to repair hi-fi kit to the highest standard is one of those 10,000 hour skills that takes commitment to master, but it is surprising what can be done with just a little patience and study.Ī basic grounding in electronics will be required, such as the ability to read a circuit diagram and an appreciation of what the various types of component do. Today's equivalent may be repairing and restoring vintage hi-fi units at home, a potentially rewarding endeavour which can make the subsequent listening even more satisfying. In the early days of hi-fi it was common to make one's own equipment, either as an economy measure or as a matter of pride. Tim Jarman on the tools and techniques you'll need to restore classic kit ![]()
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