Announcement

Collapse
No announcement yet.

Peavey XR 696F - I made a booboo

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

  • #31
    Originally posted by glebert View Post
    Were these taken with cable plugged into XR header? If so I would repeat with it unplugged. Odd the difference in the output of the +/- 15V regulators. If the 48V is still low with XR unplugged I would look at the voltage of the base of Q103, it should be about 48V there.

    These were taken without the XR header plugged in, sorry I should have mentioned that. Q103 measured 33v/85v/47v (pins 1, 2, 3, which I think is B, C, E). When I tested the Voltage regulators VR100/VR101, I noticed the ground pins all have approx -1.3v on them, in fact -1.3 is volts seems to appear on the grounds on many parts on the board.

    Comment


    • #32
      Originally posted by jondoe View Post
      These were taken without the XR header plugged in, sorry I should have mentioned that. Q103 measured 33v/85v/47v (pins 1, 2, 3, which I think is B, C, E). When I tested the Voltage regulators VR100/VR101, I noticed the ground pins all have approx -1.3v on them, in fact -1.3 is volts seems to appear on the grounds on many parts on the board.
      It looks like there are essentially two ground domains, one called GNDA and one called FGND, but they should be connected via JMP1 and JMP2. Adding 1.3V to each of the 15V rails would make those voltages seem right. The emitter voltage of Q103 seems way off, I would expect it to be just a little below the base voltage, but that transistor shouldn't screw up overall operation since it is just for phantom power. Pins 1,2,3 are BCE, but since you said you measured 33V at the XR header then it seems like the order you recorded them in might be reversed.
      Last edited by glebert; 11-15-2019, 08:12 PM.

      Comment


      • #33
        If the amp puts out DC, then the thing is already blown. The triac crowbar shorts the output. That saves your expensive speakers from cathcing fire, and it also SHOULD blow the main fuse/breaker on the amp. A hard core power down.
        Education is what you're left with after you have forgotten what you have learned.

        Comment


        • #34
          Originally posted by glebert View Post
          It looks like there are essentially two ground domains, one called GNDA and one called FGND, but they should be connected via JMP1 and JMP2. Adding 1.3V to each of the 15V rails would make those voltages seem right. The emitter voltage of Q103 seems way off, I would expect it to be just a little below the base voltage, but that transistor shouldn't screw up overall operation since it is just for phantom power. Pins 1,2,3 are BCE, but since you said you measured 33V at the XR header then it seems like the order you recorded them in might be reversed.
          I took the measurements of the 15 volt rails using FGND and they came out at a more respectable 15.2/-15v.

          I've double checked Q103 on the board and traced the tracks from the legs to the next component on the schematic, 33v/85v/47v was correct, I don't think I have them reversed. I found R119 (100k) was reading 3ohms out of circuit and replaced it. Further back down the line D104/107 are showing 87v leading to R110. R110/R116 look like a voltage divider, would it be a good idea to remove both the resistors and test them out of circuit? Below is a note of some of the voltage readings I've taken around the Q103

          Click image for larger version

Name:	Screenshot_2019-11-16_19-47-48.jpg
Views:	1
Size:	136.8 KB
ID:	856054

          Comment


          • #35
            Originally posted by jondoe View Post
            I found R119 (100k) was reading 3ohms out of circuit and replaced it.
            This is very strange. Resistors almost never short. Is it's body marked as a 100K resistor?
            Originally posted by Enzo
            I have a sign in my shop that says, "Never think up reasons not to check something."


            Comment


            • #36
              Originally posted by g1 View Post
              This is very strange. Resistors almost never short. Is it's body marked as a 100K resistor?
              It was an SMD marked 104, I double checked with a magnifying glass in case my eyes were lying to me!

              Comment


              • #37
                R110/116 are not there as a voltage divider per se, they are bleeder/balance resistors for the stacked filter caps, C110/115. The resistors make sure the voltage is equally shared between the two caps.

                At Q103 you show the 86v rail turning into 48v at the collector, and then at the base it is both 48 and 86v. Obviously this is in error. The collector should have the full 86v as they are wired together. 48v on the base seems right, as it is set by the two 24v zeners in series. 34v output is very low.

                In my 65 years of soldering, I do not recall a shorted resistor. I guess it makes more sense in an SM part.
                Education is what you're left with after you have forgotten what you have learned.

                Comment


                • #38
                  Originally posted by Enzo View Post
                  R110/116 are not there as a voltage divider per se, they are bleeder/balance resistors for the stacked filter caps, C110/115. The resistors make sure the voltage is equally shared between the two caps.

                  At Q103 you show the 86v rail turning into 48v at the collector, and then at the base it is both 48 and 86v. Obviously this is in error. The collector should have the full 86v as they are wired together. 48v on the base seems right, as it is set by the two 24v zeners in series. 34v output is very low.

                  In my 65 years of soldering, I do not recall a shorted resistor. I guess it makes more sense in an SM part.
                  Once I've had a decent nights sleep I'll go over all the measurements again. I'll take Q103 out so I can get a good look at the tracks running under it to see where they go as its possible I've crossed paths trying to follow them, maybe I should take measurements with Q103 removed. Looking over my notes I don't seem to have "ticked" Q103 as replaced, seven others have a tick but not that one, so best I take it and be sure!

                  Comment


                  • #39
                    Click image for larger version

Name:	IMG_20191117_132042525~2.jpg
Views:	1
Size:	1.22 MB
ID:	856066

                    OK I popped out the Q103, it tests fine, so i think I did replace it, but I have two spare so I can always pop in a fresh one. Measurements on the pads, left to right are;

                    0.2v / 86.4v / 48.4v

                    EDIT:

                    Is the silk screen for the transistor orientation wrong?! E should be on the first pin on the left, but the silk screen would have B on the first pin on the left, which is wrong.

                    I swapped the transistor around and it's now passing 47v

                    Now to carry on trouble shooting the rest of it!
                    Last edited by jondoe; 11-17-2019, 02:12 PM.

                    Comment


                    • #40
                      I've never seen that silk screen symbol, but I also would have read that as 1,2,3 left to right, but since R111 is connected between base and collector (1 and 2) then it has to be 3,2,1 Maybe the dashed lines are supposed to represent a heatsink on that transistor?

                      Comment


                      • #41
                        Originally posted by glebert View Post
                        I've never seen that silk screen symbol, but I also would have read that as 1,2,3 left to right, but since R111 is connected between base and collector (1 and 2) then it has to be 3,2,1 Maybe the dashed lines are supposed to represent a heatsink on that transistor?

                        It's definitely happier now it's the other way around. Looking at the Peavey schematic, there is a subtle difference in the part number for Q103, it's 2SC4793V all the others on the board are 2SC4793D. 2SC4793V is only listed once on the bill of materials. Maybe it was a short production run of reversed pin out versions? Google doesn't help, I can't find a mention of it anywhere other than Peavey related things.

                        The bright light bulb indication has now switched places. We have a bright bulb and Q107/Q110 heating up with HDR100 + J107 connected. HDR100 + J202 no longer cause a bright bulb.

                        I think I'm making progress?

                        Comment


                        • #42
                          V means vertical. OEMs can specify lead configuration. Like TDA7293 or TDA2050 cone in H and V versions. V versions have the two rows of legs bent to the thing stands up on the board. The H version has them bent at right angles so the thing can lie flat. No difference in the part, just the way the legs are bent as supplied.
                          Education is what you're left with after you have forgotten what you have learned.

                          Comment


                          • #43
                            Originally posted by Enzo View Post
                            V means vertical. OEMs can specify lead configuration. Like TDA7293 or TDA2050 cone in H and V versions. V versions have the two rows of legs bent to the thing stands up on the board. The H version has them bent at right angles so the thing can lie flat. No difference in the part, just the way the legs are bent as supplied.

                            Good to know

                            Comment


                            • #44
                              I've had a little time to poke around today, I found CR100 (1N4148) shorted, it's part of the "Off Mute" circuit (very bottom of the first page), i removed it to confirm and replaced with with a through hole with its legs cut short for now. I think Q1 (J111 N-channel) might have a problem, I read 30ohms between G to D and D to G, in either direction, I'll need to remove it to test fully. Q2 doesn't test the same and has very high resistance G to D.

                              Comment


                              • #45
                                Q1 is dead, Q106 (page 1, middle right) is also dead, currently awaiting spares

                                Comment

                                Working...
                                X