Announcement

Collapse
No announcement yet.

Another Yamaha

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    #21
    Re: Another Yamaha

    Voltages were checked with the amp turned on.
    15v was the DC voltage measured
    Q1067/8 both gave 62v to ground
    Q1067 tested 7.2v between b/e and b/c with amp off where Q1068 tested 0.45
    Last edited by No1baggiesfan; 02-09-2019, 11:24 AM.

    Comment


      #22
      Re: Another Yamaha

      Originally posted by No1baggiesfan View Post
      Voltages were checked with the amp turned on.
      15v was the DC voltage measured
      Q1067/8 both gave 62v to ground
      Q1067 tested 7.2v between b/e and b/c with amp off where Q1068 tested 0.45
      If you measured 15 volts on CB101 I suspect D1041 could be shorted
      You need to measure the voltages on the two regulator ic's ic101 and ic102. check the input and output and note the polarity also.
      Q1067/8 both gave 62v to ground ????? this makes no sense at all,
      with amp turned on
      Q1067 should have positive62 volts on the EMITTER and about Positive 55-60 volts on its collector
      Q1068 should have negative62 volts on the COLLECTOR and about 55-60 volts on the emitter.
      Last edited by R_J; 02-09-2019, 11:44 AM.

      Comment


        #23
        Re: Another Yamaha

        IC101 19.3v IN 11.97v OUT 0v com
        IC102 -6.5v OUT 18.2v COM 0v IN
        Q1067 62v 63v
        Q1068 -62.5 -61.6

        Sorry, misread my handwriting, left off the minus
        Last edited by No1baggiesfan; 02-09-2019, 12:34 PM.

        Comment


          #24
          Re: Another Yamaha

          IC102 is bad, or you are not mesuring it right. It is a negative 12 volt voltage regulator
          It should have about -18 volts IN, ground would be 0v and output should be -12v
          The pinout between positive and negative are NOT the same.

          Comment


            #25
            Re: Another Yamaha



            I will double check, but that's what I got all measured to ground.

            2nd test:
            OUT 1v COM -18v IN 0.005v

            Getting a relay click when I test the out voltage, it doesn't effect the result tho
            Attached Files
            Last edited by No1baggiesfan; 02-09-2019, 01:36 PM.

            Comment


              #26
              Re: Another Yamaha

              In that area, There is a plug W110, You can check the voltages on it. you should see +12v, ground, -12v, +18v

              Comment


                #27
                Re: Another Yamaha

                W110 showing:
                12v. 0v. -6v. 18v

                Comment


                  #28
                  Re: Another Yamaha

                  I would say that IC102 (KIA7912P) is defective. Just to be sure your input voltage is ok, check that you have negative -18 volts on C1076 or R1238
                  Last edited by R_J; 02-09-2019, 01:56 PM.

                  Comment


                    #29
                    Re: Another Yamaha

                    should the voltages of ic334, ic333, ic457 be similar?

                    Should I take out ic102 and test I out of circuit ?
                    Last edited by No1baggiesfan; 02-09-2019, 01:58 PM.

                    Comment


                      #30
                      Re: Another Yamaha

                      Of course not, they are different voltage regulators (see schematic) IC334 +5 volt 4 pin regulator. IC457 3pin +5 volt regulator, again not the same.
                      How would you check ic102 out of circuit? do you have an adjustable bench power supply?
                      Look at the data sheet for a kia7912 and you will see what is inside.
                      Last edited by R_J; 02-09-2019, 02:09 PM.

                      Comment


                        #31
                        Re: Another Yamaha

                        C1076 18.75v
                        R1238 1.4v

                        It was a suggestion from someone else, as they were 5v regulators.

                        Comment


                          #32
                          Re: Another Yamaha

                          You should be getting NEGATIVE 18.75 on C1076, and R1238 is connected directly to C1076 so how do you get a different voltage on it?
                          You should have -18 volts on both sides of R1238
                          Attached Files
                          Last edited by R_J; 02-09-2019, 02:30 PM.

                          Comment


                            #33
                            Re: Another Yamaha

                            I tested across each, sorry, it was -18 ffs
                            Ok, each to ground:
                            C1076 -18.74
                            R1238 -18.77 and -20v other side

                            Comment


                              #34
                              Re: Another Yamaha

                              Ok, that's better. I just wanted to be sure R1238 was ok.
                              Here is what is inside of that negative voltage regulator ic.
                              I am sure the ic is bad, If there was something loading the -12 volt line I suspect the voltage would be 0 and not -6volts
                              Attached Files

                              Comment


                                #35
                                Re: Another Yamaha

                                I guess the next step is to replace it and see what happens ? Or is there more to check ?

                                Quite a lot going on inside there, it's more complex than I expected

                                Comment


                                  #36
                                  Re: Another Yamaha

                                  Yes, replace it, be sure to get a 12 volt negative regulator 7912

                                  Comment


                                    #37
                                    Re: Another Yamaha

                                    Having trouble finding those here in the U.K. ��
                                    Does it have to be an exact KIA7912P or can it just be a 7912 negative 12v TO-220 ?
                                    Last edited by No1baggiesfan; 02-09-2019, 03:03 PM.

                                    Comment


                                      #38
                                      Re: Another Yamaha

                                      It is an all plastic case, correct?

                                      It does'nt need to be a KIA any xx7912 should be ok, It is a total plastic case to220, so you should replace it with the same type. Most to220 have the metal tab exposed so when monuted it would short to the heatsink
                                      The tab is connected to the input pin so it must be isolated from the heatsink
                                      Last edited by R_J; 02-09-2019, 03:21 PM.

                                      Comment


                                        #39
                                        Re: Another Yamaha

                                        Ok, thank you very much for your help and your time R_J you are a legend.
                                        I will now go and shop lol, I will update when I get it installed

                                        Thank you

                                        Comment


                                          #40
                                          Re: Another Yamaha

                                          I hope it does fix it, I can't really see anything else that would cause the problem.

                                          Comment

                                          Working...
                                          X