Where Can You Repair A Vintage Stereo

Tim Jarman on the tools and techniques you'll need to restore classic kit

In the early days of hi-fi it was common to brand one'southward own equipment, either equally an economy measure or equally a matter of pride. Today'southward equivalent may exist repairing and restoring vintage hi-fi units at home, a potentially rewarding endeavour which can make the subsequent listening even more than satisfying.

The ability to repair hello-fi kit to the highest standard is i of those 10,000 60 minutes skills that takes commitment to primary, but it is surprising what can exist done with just a picayune patience and study.

Fugitive Mistakes
A basic grounding in electronics will be required, such every bit the ability to read a circuit diagram and an appreciation of what the diverse types of component do. You'll too demand a full understanding of the potential dangers of mains-powered equipment and how to use your tools safely and effectively. There are simply no shortcuts in this preparation and y'all will get nowhere without it.

The adjacent pace is to choose what you are going to practice on. Don't make your outset mistakes on equipment that is valuable, either in sentimental or financial terms. The world is full of broken hello-fi kit and there's plenty to strop your skills on.

In choosing what to buy (or permit 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. It is ubiquitous, mostly safe and solid, gratuitous of designed-in faults and quirks and ordinarily has comprehensive service data available for it.

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A library of service sheets used to be jealously guarded by whatsoever workshop that had the resources to amass information technology, but now full manuals can be downloaded from a number of sources, normally gratuitous of charge.

Status is another factor to consider. Mint examples would be an extravagance at this phase, only it is worth seeking out pieces that are at least complete and non obviously the result of someone else'southward failed repair or upgrade attempts.

An advantage of equipment of this era is that as a rule it does not crave the blanket replacement of components to restore original performance. This arroyo is sometimes necessary in older models simply it makes every repair tedious, expensive and 1 learns aught from information technology. There is currently a fad for replacing every electrolytic capacitor in sight, regardless of the fault. This rarely solves the problem and tin can introduce many more if the replacements are the wrong blazon or fitted incorrectly.

That beingness said, you lot will soon acquire to place which components are oftentimes lacking, and be able to brand a bee-line for them once they are spotted.

Amplifier Faults
The central components in any amplifier are the output transistors, be they detached or in a chip. Diddled fuses almost always mean output transistor trouble and then bank check them for shorts before replacing the fuses or applying power. With transistor amplifiers, never connect the loudspeakers until you are sure the output stage is sound, eg, at that place isn't a substantial DC voltage present at the loudspeaker terminals.

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RCA 2N3055 output transistors [heart of image] within Leak's Stereo 30 Plus amplifier

Nigh amplifiers have a 'mid point' connection betwixt the 2 output transistors from where the output point is taken. This should exist at roughly one-half the supply voltage in designs with a single ability rail and at zero volts for those which run from dissever supplies. If this is non the example find out why earlier continuing. Ordinarily a lacking transistor or leaky diode is the root cause just other components may have been damaged as a result. If only one channel seems to be affected apply the other to take reference readings from, but be careful not to accident that one up as well!

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Early MOSFETS are used in the output stage of Hitachi'southward HA-7700 power amp

Source or monitor switches that are noisy, dirty protection relay contacts and missing pre/power amp links cause many amplifier malfunctions, so bank check the simple things like these, first. Many amplifiers have pre-fix controls for output stage bias and get-go residual. These are fine adjustments that volition tend to drift with historic period then it is always worth checking that they are right.

In the absenteeism of the maker'south data the following procedure can exist used. With the speakers disconnected, connect a voltmeter beyond one of the emitter resistors of the output transistors. Adjust the bias control for 10mV, so re-cheque (and reset if necessary) after ten minutes. After this, accommodate the first for null volts (or one-half the track voltage for unmarried-supply designs) at the midpoint and repeat the process for the other channel. This volition be close enough to the maker's specification for about models to obtain expert functioning forth with reliable operation.

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Using an insulated tool to adjust the core of the discriminator coil inside an Hitachi FT-8000 stereo FM tuner to achieve best reception

FM Tuners
These are the near reliable of vintage hi-fi components and most faults tend to exist trivial: blown bulbs, broken bulldoze cords, noisy switches and the like. A more than circuitous but common problem is an disability of the tuner to 'lock' onto a circulate, unremarkably with the result that the sound is muted when stereo reception is selected, the stereo decoder doesn't work or the digital frequency display is incorrect by a modest corporeality, say 0.5MHz. This is often due to the discriminator gyre, which forms part of the detector circuit, being in demand of adjustment.