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yamaha receiver wont power on

Discussion in 'Troubleshooting and Repair' started by fum3z, Feb 11, 2014.

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  1. fum3z

    fum3z

    3
    0
    Feb 11, 2014
    Hi!
    I've recently acquired a Yamaha htr-5440 rds receiver and I've got some problems with it. The damn thing won't power on at all. I've checked the power going to the microcontroller and it is about 4.76~4.8v. The S12 pin is at 16v and i do not have any voltages coming from the amplifier protection to the micro that could indicate a problem. On the PRY pin i've got nothing. I've also tested the 10MhZ clock and it's there.
    Hope you guys can help me and also Mark Zacharias, I know from his channel that hi's a repair tech.
    Sorry for my english, have a good day.
     
  2. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,270
    Nov 28, 2011
    Hi there and welcome to Electronics Point.

    Based on your comments, I guess you've found the service manual. If not, you can download it from elektrotanya.com. That one has schematics only.

    You can also get the data sheet for the main MCU from http://www.hqew.net/datasheet/UPD78F4218AGF-3BA-datasheet-pdf-download-50202.html

    I don't know what you mean by the "S12 pin is at 16V". Please explain. ***

    According to the service manual, the 5V rail is supposed to be around 4.8V, so that's normal.

    Let's start with the pins that the MCU needs in order to operate.

    Pins 9, 37 and 51 must all be tied to VDD. Check that there's 4.8V on all of them. ***

    Pins 40, 61 and 100 must all be tied to VSS. Check that there's 0V on all of them. ***

    -RESET on pin 43 must be high for normal operation. Itis driven by Q909. Is should go low briefly when the unit is plugged in, then it should go high. Does it do this? ***

    You say you've already checked the 10 MHz crystal oscillator on pins 38 and 39.

    Pin 7 is -WAIT but I think that function would have to be enabled by firmware before that pin would affect the MCU's operation. The MCU's basic data sheet doesn't go into this level of detail.

    Pin 21 is EXA which appears to be an output.

    Pin 22 is VPP and is pulled down to 0V. It MUST be 0V for the device to operate. Is it 0V? ***

    Pin 46 is an NMI input, but like -WAIT, this function probably needs to be enabled by firmware. This pin is used as PSW, an active-high signal from the Power pushbutton. Have you checked that pin 46 goes high while the power button is pressed? ***

    Also, does the MCU respond to the power button on the remote control? ***

    If those pins are in their proper states, the firmware should start up. Is there any display at all? ***

    It's quite possible that the MCU has been damaged and/or lost its firmware due to a voltage spike on one of its pins. None of the I/O pins are protected, and many of them go off-board via a flat cable. Some even connect directly to components that could receive a static discharge from the user's finger.

    The other possibility is that the MCU is undamaged and the firmware is present, but it is stopping part way through the startup process because of an incorrect state or response from something connected to the MCU.

    It's hard to diagnose this sort of problem because it's not always clear what the external circuitry is supposed to do. There's no circuit description and the schematic is not very well drawn either.

    So the next step would be to go through all of the pins on IC902 and try to figure out what they do, and what state they should be in.

    I'll start from pin 1 and do the first half of the pins.

    Pin 4 is 6chG which drives Q458 on the input board. It's not an input, therefore not relevant.

    Pins 5, 6 and 7 control IC351 and Q353 on a rear panel board; I think they are input selection control signals, so they're outputs - not relevant.

    Pin 8 is SCN or CSN. It goes to the DSP board but I can't find where it leaves the bus on the diagram. Can you find it? ***

    Pin 12 is called DMT. It goes to IC812 on the DSP page, into a pin called SMUTE, which I assume is a mute input. So it's probably an output from the MCU. Not relevant.

    Pins 13, 14 and 15 are PRY, MRY and ERY. They all drive transistors that drive relays. PRY drives Q161 which drives RY161 which connects the AC mains to the main power transformer.

    You said you've "got nothing" on PRY, but the MCU might drive the pin high and expect some feedback. If it doesn't get that feedback, it could drive the pin low again. So you need to check for a pulse on that pin when you press the Power button. ***

    Also, you could try forcing PRY high (disconnect the MCU pin first) and seeing whether the rest of the unit powers up. If you do this, tell me the result, including what is shown on the display. ***

    Pins 16 and 17 are RIMA and RIMB which become LC1 and LC2 and control Q662 and Q663. Not relevant.

    Pin 18 is called /MLV then /-10dB and is an output that drives Q465 on the input board. Not relevant.

    Pin 21 just detects whether headphones are plugged in. Pin 29 is just linked to 0V through a link that's presumably not present (because the pin is supposed to be at +4.8V). Both not relevant.

    Pins 35 and 36 are outputs (volume up and down, I guess). Not relevant.

    Pins 41 and 42 are for a second crystal oscillator that isn't used.

    The next pin is 44, a signal called INT928 which seems to come from IC806 on the DSP board, which is driven from a signal called IPINT on pin 153 of IC801, the DSP. I assume this is an interrupt signal and it's probably not needed for the unit to power up. Not relevant.

    Pin 45 is called PDET which sounds like power detect. It comes from R924 from Q910. I don't know what Q910 is for. It could be an undervoltage detector. Do you have any ideas? ***

    PDET comes from a 7.3V rail and would be high when power is detected, but the wire going to IC902 is marked with a zero. That seems wrong. What is the actual voltage on pin 45? ***

    Pin 47 is the input from the infra-red receiver. Check that it's high. ***

    That's the first half of the pins. You can do the same for the second half.

    I've marked all my questions with ***. Please answer ALL OF THEM.
     
  3. fum3z

    fum3z

    3
    0
    Feb 11, 2014
    Hi Kris and thank you for being interested in my problem.

    I`m going to answer to all your questions but before that i should tell you that i have the complete cpu board disconnected from the amplifier and i`m supplying 13v to the 5v regulator on the board. (thats the S12 pin on the ribbon cable)
    I don't know what you mean by the "S12 pin is at 16V". Please explain. ***
    -The S12 pin on the ribbon cable that supplies power to the cpu regulator (the stand by power) is at 16V rather than 12.7V thats shown in the schematics.
    According to the service manual, the 5V rail is supposed to be around 4.8V, so that's normal.
    -Well, in the schematics the 5.6V that are supposed to came out from the regulator is splitted in two rails, one should be at 4.8v and one at 5.2v, i have 4.8V at both of them.
    Pins 9, 37 and 51 must all be tied to VDD. Check that there's 4.8V on all of them. ***
    -Everything`s ok here.
    Pins 40, 61 and 100 must all be tied to VSS. Check that there's 0V on all of them. ***
    -Everything`s ok here.
    -RESET on pin 43 must be high for normal operation. Itis driven by Q909. Is should go low briefly when the unit is plugged in, then it should go high. Does it do this? ***
    -Yes, i have tested the reset pin with the scope and goes low when i plug in the power and then goes high as it should. Just like in the schematics diagram.
    You say you've already checked the 10 MHz crystal oscillator on pins 38 and 39.
    -I`ve tested the ceramic rezonator and got a clean sinewave and also i`ve replaced the rezonator with a crystal oscillator but without the caps and a ground pin, just for tests, and got the same signal.
    Pin 7 is -WAIT but I think that function would have to be enabled by firmware before that pin would affect the MCU's operation. The MCU's basic data sheet doesn't go into this level of detail.
    -At this time pin 7 is disconnected cause the cpu board is no longer connected to the amplifier.
    Pin 21 is EXA which appears to be an output.
    -Pin 21 is the head phones detect. I`ts a input pin, also disconnected.
    Pin 22 is VPP and is pulled down to 0V. It MUST be 0V for the device to operate. Is it 0V? ***
    -Yes it`s pulled down with a 10k resistor. I`ve just checked and i`ts 0V.
    Pin 46 is an NMI input, but like -WAIT, this function probably needs to be enabled by firmware. This pin is used as PSW, an active-high signal from the Power pushbutton. Have you checked that pin 46 goes high while the power button is pressed? ***
    -Yes, it goes high when i press the pushbutton.
    Also, does the MCU respond to the power button on the remote control? ***
    If those pins are in their proper states, the firmware should start up. Is there any display at all? ***

    -I don`t have a remote control. I`ve never checked if it does something with a remote.
    -No, i don`t have any display at all.
    -I`ve also tried the combination of buttons to start the cpu in service mode...the procedure is explained in the service manual.
    The other possibility is that the MCU is undamaged and the firmware is present, but it is stopping part way through the startup process because of an incorrect state or response from something connected to the MCU.
    -I tried to disconnect the signals going to the VFD driver, but the same...no power.
    Pin 8 is SCN or CSN. It goes to the DSP board but I can't find where it leaves the bus on the diagram. Can you find it? ***
    -Pin 8 SCN goes to the A/D converter on the dsp board and i`ts marked as an output (serial CE out for CODEC)
    You said you've "got nothing" on PRY, but the MCU might drive the pin high and expect some feedback. If it doesn't get that feedback, it could drive the pin low again. So you need to check for a pulse on that pin when you press the Power button. ***
    -There is nothing on the PRY tested with scope. If i touch the PRY pin while it`s connected to the scope i get a PWM, a perfect square wave of about 5V. But only when i touch with my fingers the pin and has no influence if i press the pushbutton or not.
    Also, you could try forcing PRY high (disconnect the MCU pin first) and seeing whether the rest of the unit powers up. If you do this, tell me the result, including what is shown on the display. ***
    -I`ve powered up the unit with a shunt on the relay and the is nothing on the display, the amplifiers are working (checked the bias and DC on the output) and the other relays are not clicking cause the`re also run from the cpu.
    Pin 45 is called PDET which sounds like power detect. It comes from R924 from Q910. I don't know what Q910 is for. It could be an undervoltage detector. Do you have any ideas? ***
    PDET comes from a 7.3V rail and would be high when power is detected, but the wire going to IC902 is marked with a zero. That seems wrong. What is the actual voltage on pin 45? ***
    -Pin 45 is power detect and i got 4.8V, the schematic is misprinted. I have no idea what Q910 is for but all the voltages are in spec.
    Pin 47 is the input from the infra-red receiver. Check that it's high. ***
    -It`s high.

    The other pins on the cpu are the data serial for the VFD driver and analog inputs for the power limiter, dc, over current...all of them are disconnected so they are low. I`ve tested them connected and with the amplifier forced running and got nothing wrong. I`m going to attach a pinout for the cpu. Thank you so far :)
     

    Attached Files:

  4. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,270
    Nov 28, 2011
    OK, you've obviously investigated this pretty thoroughly.

    What's the story with pin 29, PSM (power save mode)? It's shown as high on the schematic, and it connects to a jumper to 0V. I guess the jumper is not fitted?

    If you touch the pin you see a square wave on the scope? Is it at mains frequency? Is it caused by mains being picked up by your body? If so, that implies that the pin has not even been set to output mode. That would be done pretty early on in the firmware's initialisation.

    I think most probably the MCU is faulty or has been damaged, and/or lost its firmware, probably from an ESD event.

    I don't think I can help any further. You've tried everything I can suggest, and you've got more service information than I have. Sorry :-(
     
  5. fum3z

    fum3z

    3
    0
    Feb 11, 2014
    I guess the micro is dead and I'm tired of trying anymore.
    I've tested pin 29 with it high and low and nothing. I'm bummed cause that's a great receiver and I can't run it without that IC.
    Thank you for your help! Have a great day!
     
  6. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,270
    Nov 28, 2011
    Yes that's a real bummer. You could try advertising that you want to buy a faulty unit of the same model number, but the chance of finding one would be slimmer than a runway model :)

    You too my friend :)
     
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