Re: Question about Yamaha rx-v457 power board
OK, I most likely found the culprict. The problem is that psw from power button is missing. It goes to CB456 pin 15, which does not have anything. Also the MCU pin 74 does not have anything. However +5m reaches the MCU board from the main power supply board. I will try to jump that signal from +5M input to MCU board and jump it to syspsw at operations board trough CB456. That way MCU also should get power.
With that workaround I should get 5v and dropping of it to the correct place.
rauno45
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Last Activity: 04-25-2020, 09:16 AM
Joined: 01-03-2013
Location: virumaa
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Re: Question about Yamaha rx-v457 power board
I checked the operations board and here is what I found out: CB456 pin 18 goes to operations 1 U801. it has 3 pins. Middle should be ground and the pin on the other side does not have any voltage on it. It goes back out to CB801 and from there CB452, but with no voltage.
CB803 to CB861 is fine. Only problem I could see is that the pins going to the switch on cb861 - F1 and F2 were shorted no matter what. I could not measure +5V toggle form operations2 board anywhere. The pin on operations board named SYSPSW had 0,something...Last edited by rauno45; 01-15-2018, 02:11 PM.Leave a comment:
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Re: Question about Yamaha rx-v457 power board
I checked the ribbon cable. The pins are not bent(they look brand new as well as the sockets. Also the pins are facing the metal pins in the socket) and when measured the +5m line reaches the test point on the board that CB122 is on(behind the socket on the board).
However troublesome is that according to the schematic there should also be:
pin 4 at CB452 PRY = 10v preset
pin 11 at cb452 PRY = 0v preset
pin 14 at CB452=10V - not preset
pin 17 at CB452=5v - not preset.
So I guess there...Leave a comment:
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Re: Question about Yamaha rx-v457 power board
CB456 pin 15 does not have 5V as described before.
CB456 pin 18 has about 5 v present
The ribbon cable going from CB122 to CB452 on my model has 17 pins on all sides. As far as I can see it was connected correctly.
CB452 has S10 and 5m. 5m is on pin 1 and s10 is on pin 4.
yes cb452 pin 4 10v goes to ic452. I found it now. It is present on the middle pin(10v). There also is +5,558v output preset. From there it does not reach CB456.
I have done some tracing and found the following:
Output +5M is gotten...Last edited by rauno45; 12-22-2017, 12:56 PM.Leave a comment:
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Re: Question about Yamaha rx-v457 power board
I traced pin 15 of CB456 back to IC451 pin 74 /psw. It was missing.
I can not find IC452 right now. I suspect that it might be on the other side of the board where IC451 is situated, however taking it apart seems to be quite a hassle because this board is simuntaneously connected to 6 other circuit boards physically somehow. Isnt there an easyer way to test this?Leave a comment:
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Re: Question about Yamaha rx-v457 power board
I tested it again. There is no /psw 5v at operations board. On operations board CB801 pin 7 is 0,074V and when on button is pressed it drops to 0.
Same situation is with CB456 pin 15.
IC451 pin 74 has 0,026V and when button is pressed it drops to 0,05
So I guess the problem is that voltage from Operations board is too low?
Unfortunately I do not have the remote for this unit so I can not try powering it on from there.Last edited by rauno45; 12-12-2017, 11:48 AM.Leave a comment:
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Re: Question about Yamaha rx-v457 power board
/PSW at CB456(pin 7) gives nothing even when power on button is pressed.
CB452 -
pins:
1 - 5V
3 - 1V
4-10V
5-5V
Other pins had no volts or up to 0,20V.
cb453 - pin 5 has highest 0,25V. Other pins have about no volts(read about 0,01...0.15)VLeave a comment:
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Re: Question about Yamaha rx-v457 power board
I measured all 5V rails just in case and yes, where I tested(specified before) all three 5v rails were up.
5M = 4,973V
5BU= about 5V
5S = 4,778V
Res = 4,926V
I found Q452 on Ic board(Small SMD transistor) and it only had 0,654V on the middle pin.
Unfortunately I do not have a scope so I can not probe pin13.
I have also measured all other capacitors on the main power supply board and they were in spec.Leave a comment:
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Re: Question about Yamaha rx-v457 power board
OK, I changed the mosfet Q404 to NEC K3114 mosfet that should be eqvivalent, but this did not solve the problem, however now instead of 3V on D408 it is now about 150ish, so I guess it got better somehow, however it still does not power on and 230V do not reach big transformer.
Power on C411 also dropped to 10V which is better.
Any ideas?Last edited by rauno45; 12-07-2017, 11:01 AM.Leave a comment:
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Re: Question about Yamaha rx-v457 power board
I tested Q404 by turning it off with a G-S jumper. After that d - s reads 0,52kohms. When I activate it again with multimeter by having leads on gate and source the resistance between d and s does not change, it always remains at 0,52kohms so I guess this MOSFET is broken?
The multimeter was in diode testing mode so it should have activated the mosfet and give a different D-S reading after activation.Last edited by rauno45; 12-06-2017, 03:21 PM.Leave a comment:
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Re: Question about Yamaha rx-v457 power board
Ok, I found the +5S now from the schema. Measured after r475 from pin 55 it showed 4,8 volts
Also found out that the ground is OK. The 5V I measured was from pin 13, not 14. Was quite tricky to count the pins there.
R419 has 2,168 kiloohms.
Q404 however after I unplugged the receiver measured IN CIRCUIT that all the pins were shorted with each other. Is this something how mosfets measure in circuit or should I solder it out and properly test it? When I unplugged the power board then only the 2 side positioned terminals...Last edited by rauno45; 12-05-2017, 11:24 AM.Leave a comment:
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Re: Question about Yamaha rx-v457 power board
OK, thanks for the suggestions. I got 5v on pin 14 by having ground point on one screw connected to the metal frame of the receiver.
I will try what you have suggested(also the +5S signal) and let you know what I find out.Leave a comment:
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Re: Question about Yamaha rx-v457 power board
I found what you mentioned and here are my findings:
CB458 - 2 pins have 5 volts preset. one slightly higher, one slightly lower - 4,95 and 5,05
CB401 - reset(RES) is 5 volts when I get a good ground point with multimeter. It is kind of hard to measure down there. It did not seem to fluxuate to lower levels at all.
MCU IC451 power: schematic shows pin 14 and 64 for Vss:
pin 14 had 5,13V
pin 64 at C462 had no voltage.Leave a comment:
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Re: Question about Yamaha rx-v457 power board
Also for information that the guy I got it from said that it got a lightning strike and after that did not power up. I dont know if knowing that helps with my situation or not.Leave a comment:
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Re: Question about Yamaha rx-v457 power board
Yes, 5M rail gives almost exactly 5 Volts so I guess that the regulator somehow handles it(barelyy I guess). As C411 I have 3300uF 16V capacitor(with SMG markings)- it seems to be factory fit.
The +69V seems marked a little low for this kind of mains transformer yes.
Dumb question, but I can not find the IC451 on the power board. Is it located somewhere else where I need to check? I only see IC402 and on the schematic there is also only IC 401 and 402.Leave a comment:
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Re: Question about Yamaha rx-v457 power board
After further measurements I can say:
220V also reaches legs of C405
C411 had 17,74 Volts which is a bit high for a 16V capacitor
5M rail had 4,975 Volts
S10 had the same voltage as C411 which is a little odd. It had also the same 17,74V, alltough it should be 10.
I guess the anomaly is in the 10V rail somewhere which sets too high voltage? But where?
C406 has stabile 9Volts
CB401 PDET has 0,61 volts
CB401 PRY has no voltage.Leave a comment:
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Re: Question about Yamaha rx-v457 power board
Nope, the thermal fuse in the transformer was OK, I measured it. Continuity test between blue and grey wire was OK. There was a youtube video that instructed on fixing this, but on my unit this is fine.
I will measure C406 and other points tonight and report my findings.Leave a comment:
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Question about Yamaha rx-v457 power board
Hello,
I have a Yamaha receiver that does not power up. Does absolutely nothing. I have this far changed the common fault capacitor C405 to another 22nf 650V capacitor but that does not seem to help.
Testing the voltages I have 16 volts on C411, 5v standby is also present(excactly 5v). And AC input 230V is also present.
Only problem I have is that from the transformer leads I do not get 230V output at all. When I measure plus and - on D408 the multimeter shows only 3 Volts(testpointts marked on picture).
What would be the bad component here?... -
Re: Broken noname set top box
Got some time to test the thing a little more. Didn´t bother to check the ram chip. If its broken it will be less problematic to buy a new set top box. However one of the voltage regulators(next to heatsink) has low input voltage, that is lower than the other same mark regulators have on the board.(too lazy to find datasheet) Otherwise the regulator seems to work fine tough and i am guessing the input voltage is what is causing this junk to malfunction.Leave a comment:
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Broken noname set top box
So i have this set top box that has no name or branding or anything and it does not work. If plugged in and switched on the LED lights green. Then the TV detects input and shows a black screen. Thats all. Will not turn off, not reacting to anything. I have tryed the hairdryer trick to see if maybe some of the capacitors have high ESR , but it did not work. Maybe the problem is in the software that is loaded on there and has crashed, not the hardware? Your opinions? Worth restoring or for spare parts? I have attatched pictures below....
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