Audioclinic (Q and A) (Oct. 1973)

by Joseph Giovanelli

Record Player Used With a Timer

Q. I have recently purchased a manual turntable and a Shure M91ED cartridge.

When listening to records at night, I sometimes fall asleep in the middle of one, which results in the turntable's being left on for hours with the cartridge tracking in the end groove. Rather than continuing this unnecessary stylus wear, I have considered buying a timer which would shut off both the amplifier and the turntable at some prearranged time.

This, however, would result in the stylus remaining on the record without its rotating, for a considerable length of time.

Would this have any deleterious effect on stylus or records? If so, what would they be?

-Michael Carrano, Cahokia, Illinois.

A. If your turntable is belt driven, there will be no problem in having it turned off by way of a timer. The stylus, resting on the surface of the disc overnight, will not be harmed. Just remember that it is there, and remove it carefully first thing in the morning.

Remember that the disc, being left on the turntable all night, will have lots of time to collect dust. Therefore, be sure to remove as much of this dust from the surface of the disc as possible BEFORE YOU REPLACE IT IN ITS JACKET. Not all turntables are driven by belts.

Some are driven by idlers, wedged between the motor shaft and the inner rim of the table. If you have one of these, you must not leave the idler engaged when the table is not turning.

If you do, pressure from the motor shaft will cause flat spots to develop on the idler's surface which may not be removed during operation of the table.

The irregular motion of the idler, caused by the flat portions, will be heard as added background noise when records are played.

With a turntable of this sort, turning it off with a timer is not a good idea.

Tuner Signal Loss

Q. While playing my FM stereo receiver, I noticed that the volume was decreasing steadily. I also noticed that the reading on my signal strength meter dropped from a normal reading of 6 (on a scale of 0 to 10) to almost 0. As a result, I am led to believe that there is something wrong with the tuner section of my receiver. The amplifier still works perfectly on the phono input. I would appreciate it if you could advise on what is wrong with the tuner and what steps can be taken to remedy the problem.

-Gerard F. Tripptree, Bronx, N.Y.

A. I agree with your diagnosis that the loss of volume is the result of some problem in the tuner section of your receiver. There are any number of things which could produce the results that you have described. It could be that the main resistor feeding voltage to the tuner has increased in value, thus depriving the tuner section of its proper operating voltage. It could also be that the bypass capacitor associated with this same resistor has become leaky. A leaky capacitor causes excessive current to flow in the resistor, with a loss of operating voltage.

If you still hear normal, interchannel hiss, all of the above can be ruled out.

The tuner is receiving proper voltage.

The absence of interchannel hiss, however, does not necessarily prove the above either. Such a situation may be caused by a defective i.f. transistor or IC. If hiss is nearly normal, I suggest that you check the r.f. and oscillator circuits. Defective transistors in these circuits can cause the loss of signal as can defective r.f. bypass capacitors or open resistors.

In addition, it is always well to check for cold solder connections or small cracks in the printed circuit board foils.

Voltage regulator elements associated with the tuner circuit could be defective, leading to loss of operating potentials at some points in the circuit, again resulting in a loss of signal.

I suggest that you obtain a service manual for your receiver and use it to check for proper voltages and resistances.

Just how far you can proceed with this kind of trouble shooting will depend on your background. I certainly think anyone who is capable of working on equipment should obtain service notes when he buys his equipment. If none are available, I would personally be strongly tempted not to buy the equipment.

Channel Imbalance

Q. I own an 8-track car stereo tape player. I notice that one channel is substantially weaker than the other.

When I adjust the balance control all the way to the right and then to the left, the left channel does not match the right channel in volume. Also, when the volume control is turned all the way down, the right channel still is heard "loud and clear" if the balance control is adjusted to favor that channel. The left channel remains quiet. I know that both channels should remain quiet when the volume is turned all the way down. What causes this peculiar behavior?

-Gary De Bouver, Detroit, Mich.

A. At this time I would not want to say that your cartridge has shorted out or if something else has gone wrong.

Cartridges short out so rarely that I suggest you make some other checks before giving up on it.

Do you have a mode switch accidentally set in its "mono" position? Are you using a Y connector to mix two channels into one for making mono recordings? This arrangement can result in the loss of separation on the main outputs of some music systems.

Are there loose strands of wire shorting "hot" leads in the tonearm's shell? Look for solder bridges or for loose strands of wire which can short between the terminals (under the table) which interconnect the leads from the tonearm and the cables which feed the amplifier.

If all these checks prove negative, see if you can borrow a cartridge known to be good. Insert it into your shell as a final check to see if separation returns.

If separation has returned, the problem really is in your cartridge. I have seldom seen an occurrence.

Cartridges and Load Resistance

Q. I have just purchased a Sansui 2000A tuner amplifier. It has provisions for both a 50 K ohm cartridge and for a 100 K ohm cartridge. My turntable is a Dual 1219 with a Shure M91 E cartridge. The recommended load impedance for the cartridge is 47 K ohms per channel. Which phono input should I use?

-Carter Rhodes, Midville, Ga.

A. You should use the 50 K ohm phono input for your 47 K ohm cartridge. This slight difference between what is called for by Shure and what is supplied by Sansui is negligible and cannot be heard.

European Equalization

Q. I often purchase imported phonograph records, mainly from Germany and England. These discs would have the European equalization. My amplifier has RIAA equalization. Am I losing quality when playing back these discs? If so, is there any way to correct the situation?

-Louis Hone, Montreal, Canada

A. As far as I know, European discs are equalized just as ours are. Therefore, you should not encounter any problems in this regard when playing them.

NOTE: From time to time this column receives suggestions from readers with the thought that such suggestions would benefit other readers. The following is one such item:

Dear Mr. Giovanelli: Sometimes an electrostatic speaker will produce audible output even though unconnected to a signal source. This output sounds like "snapping" or "crackling." This is caused by corona discharge from the high voltage supply for the speaker. It may take place within the speaker itself (The 2,000-6,000 volts are insulated by only 0.001 inch of air in the wiring or in the power supply.)

Cause: high humidity, insulation breakdown, dust, cat hairs, etc.--anything that will provide a path for the high voltage to discharge or arc.

Locating: in a dark room, look inside the enclosure. (No hands, please.) You will see the arc or a blue glow of discharge.

Remedy: if the wiring has broken down, coat the wires and power supply components with high-voltage dope.

(General Cement Company makes a product called Corona Dope.) If the arcing is in the speaker and if the speakers can be taken apart, do so. Clean the speakers with a lint-free brush or cloth. Do this in a dust-free room.

In any event, let the speakers stand with the power disconnected for several days before getting into them. This will permit the high voltage to reduce to zero.

-Captain John C. Wiles, Jr., Niceville, Fla.

(Audio magazine, Oct. 1973)

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