7412533654

A

Handling Hi-Fi Service Calls

By DAVE GORDON

Audio Workshop, Inc.

Wiłh no experience ir. hi-fi work. the techniciarTs chief problem is wtoere and how fo starł checking. This technique is for house calls, where service begins.

AS THE high-fidelity market continues to expand. the electronic service technician continues to hear, again and again. that worth-while opportunities for him in installa-tion and repair arc also inereasing. Yet his own reaction. morę often than not. continues to be one of mistrust. He knows or soon learns that hi-fi repair is not the same as TV repair. He may also feel that a sizablc in\estment in specialized equipment is required for him to do a thorough job.

As to the dilTerence between hi-fi service and other types. a background in any area of electronic semce is extremely helpful—so much so that filling in the additional requirements is not an impossible task at a 11. In the matter of special equipment. a check of many hi-fi service shops in metro-politan areas reveals an mteresting point: it rarely becomes necessary to use the special instrument* ovcn when they are on hand. The experience at the Audio Workxhoi> in metropolitan New ^vork is probably typical. Al-though it is equipped with morę than adequate testing facilities including distortion analyzers. wide-band oscillo-scopes, and other instruments. this establishment does 90 per-cent of in-shop troubleshooting and check-out testing with a tcchnique that involves a generator, a wattmeter. and an oscilloscope in a special setup.

The technique involved is being withheld for a later article. Although it is important, something else comes first. in point of time. That something else is the home serviee cali. whether any of the customer’s gear eventiiallv winds up in the shop or not. In fact. the home cali is cven morę important to hi-fi work than it is in. say. TV service. For many good reasons. morę work will be completed in the home than is the case with TV. The bulk of a high-fidelity system as compared to a relatively transportable TV chassis, the importance of the specific acoustic

environment of the room in which the hi-fi rig is used, and the fact that many problems grow out of the relationship of the various components to each other rather than out of something that can be isolated to a separate com-ponent on the bench. are just some of the reasons for stress on work in the home.    '

The house cali for hi-fi.service bears many similarities to the cali for TV service. There are also important dif-ferencec:. The customer himself is like-ly to be difierent. sińce he tends to be a musie lover on the highbrow side. This need not be a difliculty if the technician has the right attitude. An attempt to approach the customer on the latter’s terms will be appreciated by him. and pay off in a good customer relationship.

The hi-fi service technician munt learn to know what he hears. He must know what real high-fidelity sounds like. His primary diagnostic tools are his own two ears and he must be ablo

I

Fig. 1. A "ttopper" resiitor lupprMiet unwanled grid pickup at Iow-leT«l itage.

Fig. 2. RC-coupled preomp input It M-pecially tentilire to unwanted noii*.

to.^udge whether the system under in-Spection is operating well, within its ^>wn particular limitations, by the use of these same ears. However. training the ear to establish consistent subjec-tive standards for good and bad sound is far less diflicult than many people assume. Prolonged listening to good Systems is important. It will teach one. for example, to ditTerentiate between “juke-box bass” that emphasizes the rangę between 70 and 100 cycles and the real item at 10 cycles or even helów. At the other end. good tweeters or amplifiers that can handle highs honestly should sound clean with no tendency toward a harsh or piercing quality.

A typical service cali starts with the customer's telephoned request for help. At this point it is necessary to get as much information as possible ahout the components in the customer s system. There are several reasons for this. Having a complcte set of model num-bers of the tuner, amplifier (and separate preamp, if presentt, record player, cartridge and speaker will en-able you to “research” these units in advance in your specialized hi-fi man-uals or file of manufacturers’ data. You will be able to get a good idea of the age of the components and the tubę line-ups. You may also anticipate a few likely candidates for replace-mont if you are sufTiciently familiar with the units in\olvcd.

When you ask Mrs. Jones what cquipment she owns. she may indig-nantly reply. “Why hi-fi of course!*’ but a little judicious digging and information as to where the model num-bers are likely to be found on the chassis will help.

Once you’ve arrieed at the customer'* home. get a “case history" of the components involved. Is the problem intermittent ? Is it experienced on the tuner or phonograph only. or on both? If it appears on the phonograph only. is it noticed at both the inner and outer

48

ELECTRONICS WORLD