How To Repair Volume Control Knob

There'southward a common issue that affects many amplifiers or integrated stereo systems with a digital volume control, where control of the volume on the forepart of the unit itself is via a physical Knob. If the volume on your stereo randomly turns upwardly by itself, or doesn't work at all, this commodity is for you.

Traditionally the volume knob was an analogue device – a potentiometer, which is a blazon of variable resistor. To put it but as a potentiometer is rotated its electrical resistance changes, thus changing the gain, or volume, of the amplifier.

Many mod devices from the last thirty years or so have switched to digital control for their functions. Thus this modify in resistance is handled not by an analogue part simply past either an electronic implementation of a potentiometer, a microcontroller, a digital to analogue converter or even a series of relays switching banks of physical resistors. Fronting all of this is the rotary encoder – a tiny function that serves as a means to send user input to the digital brain behind these clever volume controls. In essence, the encoder is actually but a fancy term for a digital knob. Despite being ane of the least complex and cheapest parts in the device in which they are used, they're probably the most prone to failure and the cause of many book-related faults in stereo equipment. Just they can be stock-still, and herein I'll show you how.

The rotary encoder is named so because it takes a user input, I.Eastward the rotation of a knob, and converts information technology into a serial of electrical pulses that tin be understood by a microcontroller – the 'reckoner' that is decision-making things backside the scenes, as information technology were. When an encoder is not being turned information technology outputs zilch – or at least, when information technology's working properly. At that place are many types of encoder simply the most common encoder used in a book control application is a very unproblematic construction.

Attached to the rotating shaft is a metal contact wheel which has equidistant slots cutting effectually its circumference. Within base of the encoder are small flexible metallic fingers. When the shaft rotates, the bike brushes against the fingers in turn, thereby producing an electrical pulse. In that location are iii pins – a, b, and ground, and by determining the direction of the pulse (A to B or B to A() we can determine the management that the shaft is being rotated. This is a simplified explanation – the scientific version involves discussion of waveforms and phase offset, but that'southward not the purpose of this commodity.

I recently stock-still a Yamaha CRX-M170 CD receiver. 1 of its faults was erratic office of the volume knob. More ofttimes than not the volume would proceed to rise to full at the slightest bear upon, no matter how much the knob was moved or which way it was turned. This is the most common symptom of this fault, though the opposite (the volume turning downwards to null) can occur, and in rare cases the knob does nothing at all. You lot may too observe that if the knob behaves sporadically, the remote control (if y'all have one) will piece of work just fine. This is a clear indication that the error lies with the encoder.

The cause of the upshot is two-fold. The encoder is normally lubricated with a grease to requite it a shine feel when information technology's rotated. But when the rut produced past the stereo system causes the grease to soften, it gradually drips downwardly the encoder shaft and coats the metal contacts, inhibiting their conductivity. The springy metal fingers in the encoder base of operations tin also get flattened with repeated utilise, and when this happens they don't consistently make contact with the rotating contact disc. When either or both are true, the pulses from the encoder are inaccurate or inconsistent, and the microcontroller cannot determine the rotation of direction or when you've stopped turning the knob. Thus, most microcontrollers assume yous're still rotating the control clockwise to heighten the book, so they go on raising the book until the stereo is every bit loud equally it will go.

Fixing the problem requires that the stereo be disassembled to gain access to the front of the encoder. This normally involves removing the front console and removing the circuit lath that contains the encoder itself and usually the display and other buttons. You'll need to utilise mechanical intuition and common sense equally information technology'south impossible to certificate specific instructions for every stereo arrangement, but the principle is the same.

You lot undertake any work at your ain risk. There are mains voltages present in these devices that tin cause serious injury or death. Always ensure that the power is unplugged, and allow some time to pass for capacitors to discharge. Use common sense. I'k not responsible for whatsoever damage you lot cause to yourself or your equipment. This article is provided for those who feel confident enough to safely undertake the steps outlined. If that isn't y'all, put down the screwdriver and detect someone to do the work on your behalf.

In the case of this Yamaha and nigh machines with a drawer-loading CD histrion, the front fascia of the CD tray should be removed first. Information technology'south easier to practice this by powering up the system, opening the drawer, shutting off the power and and so unclipping the decorative fascia before you first disassembling things. The decorative trim commonly either lifts upwardly or is unclipped and slid to the side to remove it from the tray itself.

In the case of the Yamaha six screws remove the peak console – ane at each side, and 4 at the back. In that location are five screws holding the front panel in place – ane on each side and three at the bottom. The panel so slides off and there are two cables to disconnect; i small bundle of wires connecting to the circuit lath on the bottom correct, and a flexible ribbon connecting to the dorsum circuit board.

One time you accept the front console removed, information technology's a good idea to remove the knobs themselves. They normally pull off (some are secured with a pocket-size chow screw in the side of the knob), and more often than not you'll observe some basics behind them securing the control shafts to the fascia. Remove these earlier flipping the forepart panel face up down and removing whatsoever screws holding the circuit lath in place.

You might find other hardware holding the lath in too. In the case of the Yamaha, there are a number of modest plastic clips which have to exist pushed out of the way while simultaneously lifting up on the lath. Careful test of the lath itself and the surrounding panel is the only way to determine how to remove it without breaking anything. When you do have it removed, y'all'll be treated with a site that looks something like this.

The encoder shown is the uncomplicated three-pin encoder described above. You'll notation that I've begun to disassemble this one. On near encoders in that location are four metal tabs attached to the bass that are bent over to secure the summit of the encoder. These can be pried up and to the side using a jeweller'south screwdriver. Just push them far plenty to clear the peak of the encoder, and try non to flex them likewise much – they will intermission. If you exercise break ane it'southward non a dealbreaker. Yous tin either replace the encoder for pennies, or hot glue it back together.

Once you've pried open the four tabs yous can carve up the two parts of the encoder. Yous and then accept access to the metal contact fingers and the contact disc.. Remove the shaft from the top housing and make clean away the grease with a liberal dose of electric contact cleaner. I recommend Servisol Super 10 switch cleaner as it has a lubricant that will give you a squeamish smooth encoder when it dries. You can use deoxit too if you tin stomach the price.

Make clean the contacts in the base of the encoder too and curve them upwards slightly to ensure they're making good contact. Don't get as well far with this – a slight tweak is all yous need. And so, reassemble the encoder in contrary order by carefully aligning the top plate and setting information technology in place, and bending the tabs back down. Make certain you press the tabs tightly into place so that the clamping pressure ensures that the sprung contacts maintain pressure level against the contact disc.

Y'all can then put the stereo dorsum together, reversing the steps you took to get it apart. Ensure all cables are routed and connected properly, and that the screws become back in the right holes. Once y'all're confident, power it upward and if all went well you should find you lot have a working volume control over again.

There is no definitive list of models that tin suffer this problem, though it's probably safe to say most that use a rotary encoder volition at some signal. You can tell if you have due east rotary encoder by rotating the knob by more than one complete plough. If the knob has stops at either end of its travel, it's a traditional potentiometer. If information technology rotates infinitely information technology'south an encoder.

Virtually mini hi-fi systems accept used encoders for decades including models from Sony, Yamaha, Technics, Teac, Aiwa, Panasonic, Kenwood, Pioneer, JVC, Sanyo and many others. The same goes for pretty much every AV receiver always made, every bit well as integrated home picture palace systems and a lot of modern hi-fi amplifiers. I have personally fixed a number of systems in this way including the Cambridge Sound 840A V1 / V2, 851A, 851E, various all-in-one how-do-you-do-fi systems from Sony, Aiwa, JVC and Kenwood, this Yamaha and a few others. Obviously this is non a definitive repair for every possible volume issue, but if you have a system with volume issues and information technology has an encoder it would exist the first place yous should look to find the fault.

Source: https://www.audioappraisal.com/how-to-fix-a-digital-volume-control/

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