Tip & How-To about Audio Players & Recorders

How to diagnose not having audio on the right channel of Yamaha YST-MS201












A ) Start with the input , then to the op-amp IC.







b ) check your cable like those above for continuity , ( VOM )

or use the signal tracer ( you can use any small amplifier with

speaker and point the tip of the probe on designated points

on the preamp section.

c ) then check also cable ( like one with the arrow pointed )







d ) from the cable it goes to the volume control








e ) the audio signal passes through these op-amp , see the diagram:






f ) Upon reaching pin 11 of IC TDA7370B via C444, the audio will be

further amplified and send the audio signals to your right speaker via the

cable above ( see the image ).


g) there might be a reason or a possibility that your Main Audio IC is good ,

under the following conditions:


1 ) the said IC is not overheating

2 ) the voltage on pin 14 is one-half of the supply

3 ) that there is audio input on pin 11

If it is, then

It could possibly from the capacitor ( C24 ) to the foil path going to your speaker.

Anyway you can check it with a signal tracer , only if you have one.




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2 Answers

what is a opamp


An opamp is an operational amplifer. The OPA134 is a single amplifier with differential inputs. The best way to describe this IC is that it is an ideal amplifier with infinite gain, with high input impedance and low output impedance making it both a voltage and current amplifier. The output signal is divided with resistors and provides feedback to the minus input to inject negative feedback. The ratio of this feedback basically determines the final gain. The input signal may go to the positive input for a non-inverting amplifier or to the negative input for an inverting amplifier. Roughly the voltage gain in dB will be 20 x log of Vout/Vin. There is a difference in the gain of 1 between inverting and non-inverting for accuracy sake, but that is the basics.
This particular part is very high quality in performance and should be replaced with the equivalent part or one from Burr-Brown. The power supply is typically +/- rails and ground is usually the virtual point between the split supplies representing 0V. Sometimes the input signal will not be referenced to ground and will be fed to both the plus and minus inputs which will be balanced (impedance wise) to form a differential input that rejects common signals such as noise. Pretty cool device, I couldn't live without them. OPA134 Precision Amplifier Operational Amplifier Op Amp Technical documents

Jan 10, 2014 | Texas Instruments OPA134PA IC, AUDIO,...

1 Answer

My DLP projector SIM2 DOMINO D35 is turned on and works normally BUT picture is absent on all of inputs (projector shows NO SIGNAL, green indicators is ON). Sources of signal and cables are in order. What can I do with it? Thanks


It is possible that the last time this was connected there must have been an higher input applied than is recommeded so that the input PRE_AMPS were loaded to fail.
You need to check with an signal trace on the input to find if an OP-AMP has failed or the LOGIC switching IC had failed.
Need to test using a signal tester and meter.

Jul 14, 2011 | SIM2 DOMINO D35 DLP Projector

1 Answer

phase 90 dead no led no nothing- it has tl062 and a tl064 chips block script, switch seems good on VOM, can the 2 diodes after the power input be likely problems? I can also swap out the IC chips for tl082 and tl084s if this is ok. I'm not sure actually if these ICs will work properly due to the higher power consumption rather than the 062, 064. Maybe it's a diode problem, are there zeners in this or just like 1n914s? thanks


One needs to consider the history of the unit. Could someone have used a reversed power adapter? If so they probably blew those diodes.

Input power protection diodes are often in the 1N4004 family.

Do not change any diodes without knowing the type. There may be Zeners as part of the effect shaping.

Check the power getting to the Op amps... pin 8 and 4 are the power pins, 8 being positive. Don't get fooled as sometimes the circuitry has the positive as signal ground.

ONLY SHOTGUN a device as last resort.

Dec 11, 2009 | MXR Phase 90 Pedal

1 Answer

my sansui qs 1 immediatly stopped working and alll it does is hum can not find any burnt components


Good day sir, there are several reason why the amplifier hums, but lets go to the common ones,
  1. The main power amplifier is defective. Does the volume control affect the loudness of the hum? If no, possibly replace your main amplifier IC. if its transistorized, check the two push pull amp. for shorts.
  2. If Yes, check for shorted audio cables. just maker sure you are using a good audio cable. or
  3. The pre-amp IC is defective, usually op-amps. try replacing them one at a time. these requires unsoldering and soldering.
  4. If you want to find the faulty part, you may need to trace a signal, you may need the folowing, an audio source, sine wave generator, an oscilloscope, or a portable amplifier. This method requires you to be techie. Feed the input with the audio source (disconnect first the speakers so that the hum will not bother you.) check the output of each stage, from preamp to power amp. identifying where the heck the signal dissapper. and where the start humming appears.
The third one requires a lot of work, just bring it to a service center.
Hope this helps, feel free to ask again, let me know your progress. Thanks

Jul 27, 2009 | Audio Players & Recorders

1 Answer

difference between audio amplifier & OPAMP


An audio amplifier is a general term that applies to any amplifier specifically designed to cover the audio spectrum, and usually referres to power amplifiers (of any power from micro headphone amps (like the headphone audio amplifier circuit in an ipod) . to power amps like the ones used at rock concerts that are several thousand watts).

An OP-AMP is an Operational Amplifier, which refers to a type of amplifier circuit. Op-Amps can amplify audio, but are not restricted to it. They are used in many things from audio circuitry to signal conditioning, and sensing from all kinds of equipment from seismometers, to light sensors, temp sensors, insturmentation amps, lab amps... RF amps etc...

There are many many different types of op-amps that are designed for many different applications. Mostly the parameters are frequency response, gain, and input/output impedance.

Op-amps usually come in an IC package of some sort. The most common are 8 pin DIP package types.

Op-amps do NOT handle power. (although there are some hybrid power op-amps available, they are specialty devices) The term op-amp refers to the ability of the amplifier to be manipulated mathematically by external values. (i.e. resistors set up to add, subtract, or multiply the value of the input signal) Hence the term OPERATIONAL amp, because it is performing mathematical operations on the signal. (They were first used in analog computers, allowing the voltages to be added, subtracted, and such, and displaying the resultt by directly reading the voltage value).

They handle only small signals, and require being followed by a POWER amp to do anything useful, such as drive a spleaker, or a relay, or a transducer.

For your question, most all audio amps consist of stages.

There is an input/pre-amp stage (this is usually where the eqalization, signal processing, and bass/trebel tone controls are implelented) and a power amp (output) stage that takes the signal fromthe pre-amp and raises the voltage and current to a sufficient level to drive speaker.

The input/pre-amp stage is most usually composed of a series of op-amps. Op amps also are responsible for the bass/trebel control, and the EQ.

There will most usually always be several Op-Amps in every Audio Amp.

Jun 12, 2009 | Audio Players & Recorders

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