Hafler DH-500 manual If Problems Arise

97 0 Select the .Ol mfd disc capacitor and trim each lead to 3/4". Strip two 1/2" lengths of insulation from a piece of heavy wire, and install these on the capacitor leads. Connect one lead to DB lug #l. (S-3). Connect the other lead to DB lug #4. (S-2).

98 0 Select the power switch and the .OO5 mfd disc capacitor. With the red window (or, on some switches, the #3 lug, or the separate lug) of the switch to your right, temporarily slide the white wire’s spade lug part way onto the left switch lug. Slide the line cord’s spade lug part way onto the middle switch lug. This simply makes it easier to attach the capacitor to these two spade lugs. Cut each capacitor lead to one inch (some freedom of movement is desirable), wrap one lead around the shaft of each spade lug, and solder each. Then carefully disconnect the wires from the switch.

99 0 Install the fuses. The 15 amp slo-blo fuse goes in the single fuse clip near the power switch. The four 10 ampere fuses, with the thicker elements, go into the two dual fuse clips on the chassis. If you have not already placed fuses in the speaker fuse holders on the back panel, install the 2 ampere size, for these will give good protection to most speakers. A pair of 5 ampere fuses are also included for the speaker holders, in the event your needs require very high powers. However, for steady state test signals at the full amplifier capabilities, even larger fuse sizes will be needed in the speaker fuse holders.

Now you should make a last check of all the solder connec- tions. Look closely for possible bare wire shorts, Check for secure hardware -especially that on the output termi- nals. Check that wires are not lying on top of the power resistors on the 7-lug terminal strip. Remove all pieces of solder and wire clippings from the chassis.

Three wire ties have been included in the kit which you may wish to install around groups of wires to make your finished amplifier look neat. Because it is desirable that the ground wires which connect between CL and CR be kept close together, we suggest using one tie at the base of the capacitors.

100 0 Select the front panel assembly and the power switch, and make sure that the power switch is oriented with the red window (#3 lug, or separate lug) to the right, or nearest edge. The switch is a press snap fit from the outside of the panel.

101 0 Select 4 sheet metal screws, and bring the front panel to its approximate position. Carefully attach the 3 wires to the switch lugs: white to the left; green to the right. Push the lugs fully on, and as- semble the front panel to the chassis. NEVER AT-

TEMPT TO PICK UP THE AMPLIFIER BY THE HANDLES IF THE COVER IS NOT SCREWED IN PLACE.

102 0 Select the remaining sheet metal screws and the cover. Before closing up the unit, plug it in a n d check to see that the fan turns. Because it normally operates at low voltage for low speed, a new fan may need a bit of encouragement at first. Any stiff- ness is normally overcome after a few minutes op- eration. Once you are sure it turns on each time the power switch is turned on, secure the cover.

103 0 Peel off the backing from the serial number label, and affix it to the bottom of the chassis.

CONGRAI’ULATIONS!

YOU HAVE COMPLETED ONE OF THE FINEST

AUDIO AMPLIFIERS EVER DESIGNED.

ENJOY ITS SUPERB SOUND.

IF PROBLEMS ARISE

If you are certain the problem lies in the power amplifier, check first to see that the red pilot lamp is lighted. If it is blinking at about 3 times a second, this indicates that the thermal safety breaker on one channel has shut down the amplifier because of excessive temperature. In this case, the exhaust air will be warm. After a few minutes of cool- ing, the amplifier will commence operation automatically. If it shuts down again, and the amplifier has sufficient ven- tilation, the malfunction is either internal, or is the result of an excessive (and possibly inaudible) input signal.

If the lamp is not lighted at all, the main fuse in the single fuse clip inside the chassis at the front is probably open. If

areplacement 15 ampere, slo-blo fuse also blows, the amplifier needs service, and there is a power supply prob- lem. If the relay will not close (no signal at the output, with an input signal) check for excessive DC offset (over 1.8 volts) from either channel at locations 7 or 8 on PC-9-the small relay circuit board. This indicates a defective amplifier channel, requiring competent service. If there is no indication of excessive offset, the fault is in the relay or on the PC-9 circuit board.

On rare occasions with some arm/cartridge combina- tions, very high signal levels at subaudible frequencies may cause the relay to cut off the output briefly, because the sensing circuit sees this as DC offset. If this is annoy- ing, and you are willing to accept a little less relay protec- tion, you you can change R107 and R108 to a higher value. These are now each 39000hms (orange, white, red) and are located above the IC on the small circuit board PC-9A. We suggest 4700 ohms as the next step. At the other extreme, it is possible to increase the sensitivity so that the relay would protect the speaker if a stylus were dropped on the record, but then it might be activated by powerful low fre- quency transients.

If the fan does not turn, or makes a ticking noise, make sure it is properly centered in its supports, and that ship- ping abuse has not twisted it so the blades are rubbing the housing. Moderate pressure on the struts will recenter it.

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