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The mechanical end-of-play sensor (trip pawl) is activated by a lever attached to the underside of the tonearm. Make sure it's resetting to neutral when a cycle is completed.

Many turntables as they age allow vibrations from the motor to feed into the plinth, and from there into the tonearm and the cartridge. This is often due to deteriorating mounting grommets for the motor itself. The grommets often get hard, so that instead of absorbing the vibrations they...

The dominant failure on the Garrards of that era----and the Zero 100 gets this disease severely----is that the amber-colored grease changes into bubble-gum, and the speed selector and cycling mechanism freezes up. It takes a seasoned technician about four hours to property service a Zero 100...

As elnaldo notes, there should not be a 4-ohm discrepancy between the two speakers. An 8-ohm IMPEDANCE speaker will measure about 6 ohms on a digital multimeter, like a Tenma or Fluke, which only measures the resistive component of the 8-ohm impedance. So . . . actually I'm wondering about the...

Good idea to change out the coupling cap in the other channel as well. Fred

Yeah, this is a repair for a customer, and he specifically wants the soft clipping to work. I've seen scores of these over the years, but this is the first time the little non-linear gizmos got killed. This model not only does soft clipping it has a totem pole power supply with switching...

Hello all, In order to do the soft clipping, NAD uses non-linear elements, one each in the positive and negative supplies. The part number is RDE185A. So far, these devices appear to be "unobtainium". A company called onlinecomponents.com shows the above part number as "active", but they do...

One thing to do right off is to raise the unit higher off the shelf beneath, so that cool air can more easily enter. I don't think there's room near the power supply board to install an internal fan, and that's where cooling is most needed. As I recall, there isn't much airflow between the...

A great many Pioneer power supplies are underrated relative to their positioning and ventilation. Thus, they cook themselves. In rebuilding them, always use 105 degree caps, and be willing to use transistors with slightly higher power ratings (but with similar bandwidths.) The SX-1980 is...

I recommend Nichicon and Panasonic caps. Make sure to use 105 degree caps on the regulator and power amp boards. Fred owner Classic Audio Repair

Recap it in stages, not all in one fell swoop. And do the power supply first with special attention to the regulator board. Test the set after each stage of recapping. Fred owner Classic Audio Repair

The gains (HFE or beta) on the differential amplifier transistors need to be matched within 5% or there will be an offset voltage that may not be eliminated via adjustment. At my shop, we often get them matched down to 1%. It really does make a difference. Fred owner Classic Audio Repair

You will also need to rework the headshell. The four metal contacts in the shell should be reinforced with dabs of epoxy, since they are only held in position by four little plastic nubs -- that become brittle with age. There are EIGHT crimps in the headshell. These oxidize internally and lead...

Got one of these in that has a murdered voicecoil. All of the regular places we get speaker parts from have failed us, and nothing real turns up on the internet other than refoaming kits. anyone know where a recone kit for a JBL 112a woofer can be acquired? Cost is not an issue. Thanks!

Good work so far. Make sure you treat (clean) the switches and controls with Caig DeoxIT D5. Fred repairing audio gear since the Pleistocene

It appears from your description that the failure is on the left-channel record PCB. Look to see if there's an IC. If there is, that's probably the problem, but good luck on finding the device. If there isn't, the failure will be either a transistor or an electrolytic capacitor. * * * * *...

It is unlikely that caps have gone bad. Unfortunately a great many parts for the entire RS-1500 series of R2R's were scrapped around 1990, while I was a manager in the Panasonic service division (Technics was a Panasonic product.) People like myself protested, but the Finance guys in New...

I am a licensed second-hand dealer, as well as owner of a repair service for audio gear. I buy vintage receivers regularly. Here's what I look for as far as visible details (rather than what happens when I plug it in.) (1) Is the set rusty? In San Diego, lots of people live near the beach...

I concur with the "bad power switch" suggestion. Mouser and Digi-Key have good selections of power switches, although you may need to do a bit of light machine work. Omron switches are an excellent brand, as they were OEM in many vintage receivers. Otherwise, you may need to cannibalize a...

In general, capacitors will not cause hissing. As dr*audio indicated, this is normally due to noisy transistors and IC's. Because the problem increases and decreases according to your volume control setting, the origin of the problem is in the preamp. Touchy switches and noisy controls are...

Treat the switches and controls with Caig DeoxIT D5. You can do a search here at AK and learn the proper procedure for this. Also, burnish the contacts on the protection relay. Again, a search will turn up the proper way to do this. Touchy switches, noisy controls, and oxidized or pitted...

Thanks to all!!!!! I have entered the third-trimester. Scary. Fred "repairing audio gear since the Pleistocene"

I recommend you first restore the amps to "stock" before you contemplate mods. Stock performance will give you a point of reference, or a baseline, from which it will be relatively easy to judge whether the mods improve the sound (or the reliability), or whether they do not. One reason I...

Several years ago I began noticing that on McIntosh tube power amps, such as the MC-240, where the main power supply cans were grounded to a diamond-shaped plate, and then the plate was riveted to the chassis, that over the years the connections between the plates and the chassis oxidized. Thus...

Need a schematic!!!! This is a preamp with a solid-state power supply and tubes for the signal path. Counterpoint is no longer in business, and I've searched high and low for service information. Evidently someone who used to work for the company has acquired the original manuals and wants a...