I have a yamaha rx-v870 that I believe has a bad stk 4151v chip in it. If that board is plugged in the amp never comes out of protect. If that board is un plugged the amp doesn't get any signal to make a sound but does come out of protect.
I am thinking that is the culprit, but can someone point me to where I can test it - like pin 6 and 1 should be 3.3 ohm, not 0. Like that.
Thanks.
Srinath.
I am thinking that is the culprit, but can someone point me to where I can test it - like pin 6 and 1 should be 3.3 ohm, not 0. Like that.
Thanks.
Srinath.
You can check some of the STK module's transistors with a multimeter. Usually the output transistors short or open. Also look for matching multimeter readings comparing between channels.
Multimeter (+) to the first pin in list.
Meter on diode test:
Pin 13-12 and pin 13-15 open. Pin 12-11 and pin 15-16 open.
Meter on ohms:
Pin 13-2 and pin 13-21 high on ohms (I'm not sure what R9,R19 are on the chip)
Pin 2-7 and pin 17-21 some R reading (not open)
This works for STK4141,STK4151,STK4161,STK4171,STK4181,STK4191,STK4201,STK4211 family... STK4151 datasheets pdf
Multimeter (+) to the first pin in list.
Meter on diode test:
Pin 13-12 and pin 13-15 open. Pin 12-11 and pin 15-16 open.
Meter on ohms:
Pin 13-2 and pin 13-21 high on ohms (I'm not sure what R9,R19 are on the chip)
Pin 2-7 and pin 17-21 some R reading (not open)
This works for STK4141,STK4151,STK4161,STK4171,STK4181,STK4191,STK4201,STK4211 family... STK4151 datasheets pdf
Priariemystic: I will check it with your idea.
Gmphadte: The inv and non-inv inputs, are they output of the stk - see there is like 4 connectors with 2, 3, 4 and 5 pins going to the board.
I will look on the schematic and the circuit boards and test it. It was made in the mid 90's if I am right. I am pretty sure the stk is bad, but in firther fiddling I did after I figured it was bad, I may have damaged more stuff.
Thanks.
Srinath.
Gmphadte: The inv and non-inv inputs, are they output of the stk - see there is like 4 connectors with 2, 3, 4 and 5 pins going to the board.
I will look on the schematic and the circuit boards and test it. It was made in the mid 90's if I am right. I am pretty sure the stk is bad, but in firther fiddling I did after I figured it was bad, I may have damaged more stuff.
Thanks.
Srinath.
OK I got the new stk4151V chip and swapped it in.
The amp turns on and stays on if I leave connector "CB109" - Bottom left of pic unconnected.
If I connect it it turns on and 5 sec later shuts off. From past experience it has been a transistor shorting to ground, except in this case, the stk4151 has not even been screwed into the heat sink, I have tried it off the heat sink and it still shuts off.
Unplugging or plugging in any of the other 3 has no effect. What could be going on, and I also have a stuck relay RY104 - Its stuck open, not closed. So I thought it would just not make sound, but can that cause the amp to not stay on ?
Thanks.
Srinath.
The amp turns on and stays on if I leave connector "CB109" - Bottom left of pic unconnected.
If I connect it it turns on and 5 sec later shuts off. From past experience it has been a transistor shorting to ground, except in this case, the stk4151 has not even been screwed into the heat sink, I have tried it off the heat sink and it still shuts off.
Unplugging or plugging in any of the other 3 has no effect. What could be going on, and I also have a stuck relay RY104 - Its stuck open, not closed. So I thought it would just not make sound, but can that cause the amp to not stay on ?
Thanks.
Srinath.
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The STK should be mounted to the heatsink before powering on ,
otherwise they may get in a thermal runaway , dont know if there s
a protection in such a case.
As for the output relay , it is normaly open a few moments
at power on before the temporisation switch them on unless
the power module has a default , typically too high output
DC offset.
otherwise they may get in a thermal runaway , dont know if there s
a protection in such a case.
As for the output relay , it is normaly open a few moments
at power on before the temporisation switch them on unless
the power module has a default , typically too high output
DC offset.
Try a few things
CB109 is the power connector for the STK modules. If it's unplugged, RLY104 doesn't have power and can't pull in. CB103 is to the speaker protection logic and if it's unplugged, RLY104 won't get the signal (SPR) to pull in.
With CBL109 and CBL103 in, ensure the STK's have around OV on their outputs. Otherwise, DC voltage there will go through DCDT on CBL103 and tell the protection logic to shut down.
Check R275, R268 as these look like fusible resistors.
CB109 is the power connector for the STK modules. If it's unplugged, RLY104 doesn't have power and can't pull in. CB103 is to the speaker protection logic and if it's unplugged, RLY104 won't get the signal (SPR) to pull in.
With CBL109 and CBL103 in, ensure the STK's have around OV on their outputs. Otherwise, DC voltage there will go through DCDT on CBL103 and tell the protection logic to shut down.
Check R275, R268 as these look like fusible resistors.
R275 and 268 were literally on the nose for their ohm value.
The protection relay - we're not even going that far as yet, with 109 plugged in, the amp turns itself off 5 sec after you put it on.
With 109 unplugged the amp stays on, but safety relay doesn't click.
Now the RL104 is stuck, I doubt it will ever click on ... I have in fact opened relays and seen them work, or in fact not work, they are typically blown up or have burnt coils or something, however this guy is stuck, well, I am probably going to check for voltage on the coil and worry about getting a replacement.
Anyway, plug in 109 and the amp turns off.
Thanks guys.
Srinath.
The protection relay - we're not even going that far as yet, with 109 plugged in, the amp turns itself off 5 sec after you put it on.
With 109 unplugged the amp stays on, but safety relay doesn't click.
Now the RL104 is stuck, I doubt it will ever click on ... I have in fact opened relays and seen them work, or in fact not work, they are typically blown up or have burnt coils or something, however this guy is stuck, well, I am probably going to check for voltage on the coil and worry about getting a replacement.
Anyway, plug in 109 and the amp turns off.
Thanks guys.
Srinath.
OK I lied -
R275 and R268 - I measured something else and thought I had measured these.
OK these 2 on my rather inaccurate DMM, you know one of those $3 harbor freight ones, which is desiged to read 200 ohm minimum it read 0.8 ohm on both of these. They both look nice, not burnt. So I guess I am not sure about these 2. Now can they blow themselves to where they have higher resistance or do they simply blow open ? and I guess if they are open, I could be reading .8 ohm from the other components in the circuit.
I guess I gotta pull em and test em again.
Thanks guys.
Srinath.
R275 and R268 - I measured something else and thought I had measured these.
OK these 2 on my rather inaccurate DMM, you know one of those $3 harbor freight ones, which is desiged to read 200 ohm minimum it read 0.8 ohm on both of these. They both look nice, not burnt. So I guess I am not sure about these 2. Now can they blow themselves to where they have higher resistance or do they simply blow open ? and I guess if they are open, I could be reading .8 ohm from the other components in the circuit.
I guess I gotta pull em and test em again.
Thanks guys.
Srinath.
Pulled off
OK I pulled those resistors off the board and they read 2.0 ohm on my inaccurate DMM.
With those out and c109 connected the amp still shuts off.
Then I pulled out the stk4151. The amp still shuts off when c109 is connected.
I am now thinking the problem is ahead of c109. And this is where it connects to the rest of the amp.
I am thinking it could be either of the 2 caps or that rectifier bridge - I should get clean DC out of those right - what happens if its not good DC, like its got too much fluttering (what is the right word for ac mixed in with DC ?)
Thanks.
Srinath.
OK I pulled those resistors off the board and they read 2.0 ohm on my inaccurate DMM.
With those out and c109 connected the amp still shuts off.
Then I pulled out the stk4151. The amp still shuts off when c109 is connected.
I am now thinking the problem is ahead of c109. And this is where it connects to the rest of the amp.
I am thinking it could be either of the 2 caps or that rectifier bridge - I should get clean DC out of those right - what happens if its not good DC, like its got too much fluttering (what is the right word for ac mixed in with DC ?)
Thanks.
Srinath.
OK The voltage @ cb109 is +/-60v, Its supposed to be 33.
Its getting from the trafo 45vct, like 22.5 and -22.5 Its a bit low, supposed to be a bit over 24. Anyway, and out comes 60v, so what can cause the voltage to shoot up like that - bad rectifier bridge ?
Basically in that pic, where they is supposed to be 49v ac, I got 45v ac, and where there should be 33, I got 60. What could be going on ?
Thanks.
Srinath.
Its getting from the trafo 45vct, like 22.5 and -22.5 Its a bit low, supposed to be a bit over 24. Anyway, and out comes 60v, so what can cause the voltage to shoot up like that - bad rectifier bridge ?
Basically in that pic, where they is supposed to be 49v ac, I got 45v ac, and where there should be 33, I got 60. What could be going on ?
Thanks.
Srinath.
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And Grrrrr fuses blown ... both of em ...
Man It was fine and I was getting 60v where I should get 33.
Then for a while when I soldered it back I was getting low voltage, like 6-7v, then I figured I soldered the rectifier bridge backwards, and I flipped it around, that made it blow I am guessing.
So now ok I dont remember which way the rectifier bridge was installed. So, can I cause any damage putting it in in reverse - but its the flat 4 prongs in a line type, the 2 center ones are for the ac from the trafo, the outer ones are for the output "mmmmmmmmm" voltage - 1/2 rectified. So can it have any issues with installing it in reverse ? Thanks, and I cant believe you (priariemystic) knew my fuses were blown when I didn't. Yea yea I know fundamentals ... which is why I ask here over and over again even when no one has posed to my posts heh ...
Cool.
Srinath.
Man It was fine and I was getting 60v where I should get 33.
Then for a while when I soldered it back I was getting low voltage, like 6-7v, then I figured I soldered the rectifier bridge backwards, and I flipped it around, that made it blow I am guessing.
So now ok I dont remember which way the rectifier bridge was installed. So, can I cause any damage putting it in in reverse - but its the flat 4 prongs in a line type, the 2 center ones are for the ac from the trafo, the outer ones are for the output "mmmmmmmmm" voltage - 1/2 rectified. So can it have any issues with installing it in reverse ? Thanks, and I cant believe you (priariemystic) knew my fuses were blown when I didn't. Yea yea I know fundamentals ... which is why I ask here over and over again even when no one has posed to my posts heh ...
Cool.
Srinath.
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