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Yamaha HTR-5450

Discussion in 'Troubleshooting and Repair' started by carlosraj7, Nov 9, 2019 at 4:39 AM.

  1. carlosraj7

    carlosraj7

    4
    0
    Aug 20, 2014
    Hi

    I need help with troubleshooting this Yamaha HTR5450 AV Receiver. When press Power ON, it shuts off within a sec. I downloaded the manual, and referring to the manual I entered the self diagnosis mode. In this mode, it shows "PS PRT 060" . Upon opening up the amp, the +5V and +12V regulators were blown. I replaced them and then it started working normal. The sound on the left channel was intermittent and I realised it was the relay contact, so opened up the whole amp and replaced the relay. Now after putting back the amp, it powers up and turns off within a second again. In the diagnosis mode it shows "PS PRT 000". upon entering the sub menu it shows "DC > 026 PS > 000". I think it indicates a power supply problem, but upon checking , all the regulators are OK and the +12V, -12V, +5V and +25V and -25V are present. the high voltages to the power amp read +54V, -54V. I do not understand why it is showing PS as 000. Can someone please assist.

    Thanks
     
  2. 73's de Edd

    73's de Edd

    2,723
    1,114
    Aug 21, 2015
    Sir carlosraj7 . . . . .

    If you have the manual at hand, check on ADOBE page 48 and drop down to the Rear left amp and refer to its mark up, as its small VIOLET squares being used, are less invasive of blocking the view of the schematics wiring traces.

    Note the distintive dual 2.2 ohm emitter resistors and their ease of being spotted around the board locations..
    If all is well in the amplifiers of the respective different 5 amplifier sections, that emitter center voltage will be balanced out from its +52 and -52 amp power sources and be very close to zero volts.

    That voltage is being sampled by R82 ( over to the right of Q29 ) and it feeds out to shared line that runs up and down the schematic and ties into a shared OVERVOLTAGE protection circuit.
    I think THAT OVERVOLTAGE , will be the ocurring situation of interest .

    FIO . . . . there are additional OVER CURRENT and excess peak voltage detector circuitry portions also involved.
    For OVER CURRENT, R68 is detecting the Q18C emitter current consumed and feeding to Q29 base to reflect an excess change, by the collector voltage change in the R81 resistor, which has its other end connected to another shared line running up and down between like sections and is tied into a shared OVERCURRENT protection circuit.

    Lastly is the possibility of a squirrely or intermittent wiring connection in a line transferring audio output power to a speaker.
    At an instant of loss of connection, the normal loading of the speaker disappears and the voltage level skyrokets up..
    That circuitry is seen as being the R60 sampling resistor , the D3 steering diode and bit of damping is provided by the R84 / C25 series pair before that line dumps into another shared PEAK DETECTION line that runs up and down the schematic between the other sections like circuitry.

    So, initially power up and check for that FIRST, OVERVOLTAGE condition, as I feel that will be your specific type of protectiion circuit activation , which is causing your problem.

    You need to test for voltage where I mentioned, at TEST, since all of the speakers are isolated from the amp sections by different relays, and they will not let a FULL +52V or -52V go to your speaker voice coil,as a worst case, if there is an OVER VOLTAGE-OVER CURRENT or EXCESS PEAK VOLTAGE fault.

    You now have 5 amp sections TEST points to check for unwanted DC voltage presence.


    REFERENCED AREA SNIPPET . . . . .

    upload_2019-11-9_5-42-25.png


    73's de Edd . . . . .

    Early to rise and late to bed makes a man unhealthy, wealthy and dead.



    .
     
  3. carlosraj7

    carlosraj7

    4
    0
    Aug 20, 2014
    Earlier I stripped the power amp board and checked every component, they all checked OK. According to the manual, if there is a DC voltage leakage or component failure in the power amp circuit, the amp will shut off only in 3 secs, but this shut down is within 1 sec and the diagnosis menu (menu 11, AD data Check will show DC value and PS value. For normal operation, the DC value should be between 3 to 35 and the PS value between 120 to 170. Earlier when the amp was working normal, the DC value was 27 and PS value 140, now the DC value shows 27, which is within range but the PS value of 000 is abnormal. I guess the problem has something to do with this abnormal PS reading. Not only the power amp but I have checked all the voltage regulators and power supply board as well. It seems the CPU is not detecting voltages. All grounding points are tied to ground, I do not know if I missed any.

    Thanks
     
  4. 73's de Edd

    73's de Edd

    2,723
    1,114
    Aug 21, 2015
    BUT . . . .Have you powered up and taken A DVM and checked those DC voltages at those 5 TEST points . . . .and what were they reading ?
     
  5. carlosraj7

    carlosraj7

    4
    0
    Aug 20, 2014
    Yes sir, I took the readings at the centre pin of all these five 0.22 ohm resistors to ground with a DMM, they read between 0.5mV to 1.1mV except R53 that reads 7.8mV. The readings were taken with the amp on DIAG mode.. I guess the readings are OK. My worry is why is the PS reading show 000, which means 0V. I am wondering from which point the CPU monitors the PS reading, so I can trace from that point to see if any component failed or a break in the circuit.

    Thanks
     
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