Hello,
Im new here, and i hope someone can help me with my problem.
Like the title says, i have 2 Yamaha HS80M studio powered monitors, on one of them woofer does not work, only tweeter. I have a PDF file of service manual, but im not smart enough to figure all out. I did try woofer speaker on my other monitor, and its working fine. So i know its not the speaker, it has to be the amp part. One thing that i noticed is while this monitor is playing music and i unplug it from the power outlet, the woofer will play sound for a sec and then dies together with twitter, as there is no power. Im thinking that there may be some bad capacitors, but visually i didnt see anything bad. If anyone can point me towards the right direction on when to start troubleshooting, i would appreciate that. Here is the link on PDF service manual.
Im new here, and i hope someone can help me with my problem.
Like the title says, i have 2 Yamaha HS80M studio powered monitors, on one of them woofer does not work, only tweeter. I have a PDF file of service manual, but im not smart enough to figure all out. I did try woofer speaker on my other monitor, and its working fine. So i know its not the speaker, it has to be the amp part. One thing that i noticed is while this monitor is playing music and i unplug it from the power outlet, the woofer will play sound for a sec and then dies together with twitter, as there is no power. Im thinking that there may be some bad capacitors, but visually i didnt see anything bad. If anyone can point me towards the right direction on when to start troubleshooting, i would appreciate that. Here is the link on PDF service manual.
First you should determine if it's the speaker that's bad, or the amp section that drives the dead woofer. Since you mentioned that there was a short burst of sound when the unit was switched off (unplugged), it sounds to me like the amp is bad rather than the speaker driver.
what sort of test equipment do you own?
i'd try injecting signal at pin 1 of CN 602 to see if the amp is ok.
from what you've described i'd try replacing C157 10uf 50v capacitor it's on the output of IC 106 which drives the LF section amp.
i'd try injecting signal at pin 1 of CN 602 to see if the amp is ok.
from what you've described i'd try replacing C157 10uf 50v capacitor it's on the output of IC 106 which drives the LF section amp.
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I have a multimeter with that have capacitor mode.
Today i disconnected all PCB boards and swapped amp PCB from other monitor, and it worked fine. So that tells me that something is wrong with AMP PCB. From what i understand the capacitor you are referring is on input PCB, right? C157 measures 10.45 uF.
Today i disconnected all PCB boards and swapped amp PCB from other monitor, and it worked fine. So that tells me that something is wrong with AMP PCB. From what i understand the capacitor you are referring is on input PCB, right? C157 measures 10.45 uF.
ok that confirms that signal is making it through the input stage and that the problem is in the amp module.
have you checked supply voltages to IC 601? and verified there's no dc on the low out?
have you checked supply voltages to IC 601? and verified there's no dc on the low out?
I get 62.5v between pin 4 and 5, and 0v between pin 9 and 10. These numbers are the same on both IC601 and IC602.
it would be better if you take these measurements with reference to ground.
so far though the chips are seeing power.
any dc on pin3 of IC 601?
and pin 8?
and just to be sure, your checking the faulty board, correct?
so far though the chips are seeing power.
any dc on pin3 of IC 601?
and pin 8?
and just to be sure, your checking the faulty board, correct?
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Nothing at pin 3,
Pin 8 reads -3.2v
and between pin 5 and ground is 29.5v (is it normal? because between pin 4 and 5 its 62.5v)
Pin 8 reads -3.2v
and between pin 5 and ground is 29.5v (is it normal? because between pin 4 and 5 its 62.5v)
what are you getting at pin 8 of IC 602?
and yes the reading at pin 5 is normal (with respect to ground what do you read at pin 4)
and yes the reading at pin 5 is normal (with respect to ground what do you read at pin 4)
Never mind, sorry. I was measuring using ground from middle pin on connector CN805 thats why i got -3.2v, but if i measure from pin 6(ground) on IC601 or IC602, pin 8 reads 0v. I hope thats clear.
Edit:
Isn't common ground supposed to be the same? Im little confused now on where to take my ground from.
Edit:
Isn't common ground supposed to be the same? Im little confused now on where to take my ground from.
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the middle pin (pin2) of CN805 is a ground
pin 6 is N.C. (not connected) and not a usable reference.
if you keep changing up things it's going to be more difficult to help you.
you still need to tell me what your reading is on Pin8 of IC 602 (use the middle pin of CN805 please)
pin 6 is N.C. (not connected) and not a usable reference.
if you keep changing up things it's going to be more difficult to help you.
you still need to tell me what your reading is on Pin8 of IC 602 (use the middle pin of CN805 please)
that leaves troubleshooting the"limiter" portion of the circuit.
are you capable of testing the transistors?
are you capable of testing the transistors?
if it requires a special tool to test them, than no. I have a multimeter.
What's the voltage supposed to be at pin 8? I try to compare all values to my other good monitor, and so far its all the same.
What's the voltage supposed to be at pin 8? I try to compare all values to my other good monitor, and so far its all the same.
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without knowing your meter i can't say that it's capable of it either, some have a diode test function that would allow you to do quick in circuit verification of the transistors.
if this sort of testing is unfamiliar to you then i do suggest turning this over to someone more qualified.
please exercise caution i don't want you or your device to come to any harm!
if this sort of testing is unfamiliar to you then i do suggest turning this over to someone more qualified.
please exercise caution i don't want you or your device to come to any harm!
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