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Sony STR-DB940 pulled back from the brink

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    #41
    Re: Sony STR-DB940 pulled back from the brink

    Originally posted by RobBerry23 View Post
    I did put my finger on one of the connections when it was playing music and it did get louder instantly but gave a nasty shock :/

    Re soldered that particular joint but it has not helped. So I kinda need to know how to test each joint.
    You need to inspect the joints carefully, or just reflow the lot in that area.
    Take a careful look at the joints in the center of the attached photo, from my STR-DE545.

    You should be able to see the cracks around the joints, halfway up. I reflowed all which looked suspicious, adding a touch more solder to each one to give some fresh flux. Most were around the main power ICs which generate a fair bit of heat. If that does not fix it, you may have a faulty component instead.
    Attached Files
    "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
    -David VanHorn

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      #42
      Re: Sony STR-DB940 pulled back from the brink

      Been trying to look at the solder joints but my eyes are terrible, as is my soldering skill,

      I have purchased a mains testing screwdriver but it doesn't appear to work on the amp main board or I am using it wrong, I am unsure,

      Giving it a good inspection now and will hopefully find some bad solder joints somewhere,

      My sub has also now gone really quiet as well, not sure where pins that need to be soldered are for these two, can anyone tell me/show me?

      Thanks

      Rob

      Comment


        #43
        Re: Sony STR-DB940 pulled back from the brink

        Have had a whack at the joint I thought was the problem, The Sub is now working fine, but none of the speakers seem to work at all now, Both in the A and B sections of the amp, I believe I have damaged a bit of the green circuit board by pressing too hard on one side and it is lifted upwards slightly compared to the rest of the board.

        Looks like its time to get looking for another Amp, Shame. Will give it another try soon, but it seems like a lost cause,

        Anyone know of a similar amp to this for around £50-100. Would like to stick with Sony if possible as this amp has been amazing for the past 5 years I have had it

        Comment


          #44
          Re: Sony STR-DB940 pulled back from the brink

          Has anyone here had any experience with the DA1200ES? Have been offered one in very good nick for around £70. Looks like a cracking amp from reviews around, I have no use for HDMI inputs really but it looks like a more future proof investment as I cannot afford anything over £150 realistically?

          Thanks

          Rob

          Comment


            #45
            Re: Sony STR-DB940 pulled back from the brink

            Couldn't fix the amp so have managed to pickup a good condition Onkyo TX-SR576, Doesnt seem to be quite as loud as the sony from what I can tell, but is still good for what it is I suppose.

            If anyone needs an STR DB940 for spares I am posting it on ebay in 24 hours.

            Thanks

            Rob

            Comment


              #46
              Re: Sony STR-DB940 pulled back from the brink

              Ok. Just got some proper speakers for this amp and I've been able to test the thing. The sub channel was already dead when I got it, but now it seems to have developed another problem.

              When I plug in an ipod with a 3.5mm headphone jack to rca the right front channel is very quiet on stereo and all the surround modes. If I select mono the front speakers have the same volume?

              I remember a few nights before that surround on optical was running fine. Haven't had a chance to recheck if this has changed mind you.

              Does anyone know why this might be happening and what I can do to fix it? It seems this particular amp has issues in this area.

              Also. Is there a way I can do an overall test/diagnostic with this amp to make sure that all channels are working correctly.

              The speakers I got to go with it are a complete mismatch. Ill post the details about them on here later when im back from work.

              Thanks
              Last edited by trydowave; 04-25-2014, 05:26 AM.

              Comment


                #47
                Re: Sony STR-DB940 pulled back from the brink

                Originally posted by Furball View Post
                Result

                4mins work with the soldering iron and job done, all points can be got at via the removeable panel underneath.
                It took longer to disconnect and remove the amp from the AV rack than it did to solder up the relays

                So far its been running for about 20mins and hasnt clicked or dropped a channel once so recon its cured, also the centre speaker output quality has improved by 50% at least, I just hadnt realised how bad it had got

                Many thanks to Ethan and the others who have contributed and for anyone else with the same problem heres a pic of the underside of the amp with the relay points that need touching up in RED, the YELLOW dots are a set of connectors that I also touched up as they looked a bit rough.



                I've also added it as an attachment just incase the host of the above drops out

                Right time for a film I recon

                Furball


                Thank you so much for this info. I have fixed about 4 DB940's so far for sound dropout, and every time, this has been the problem. Kudos!! Such an easy fix too, with the access panel on the bottom. Appreciate the diagram!

                Comment


                  #48
                  Re: Sony STR-DB940 pulled back from the brink

                  Hi there. My speakers have just blown. They were Memorex 305 100w speakers.
                  Does anyone know what speakers would go well with this amp? Would a pair of Jamo E550s be ok?

                  thanks
                  Tony
                  Last edited by trydowave; 12-22-2014, 07:45 AM.

                  Comment


                    #49
                    Re: Sony STR-DB940 pulled back from the brink

                    Can't see why not, just make sure it's not an amplifier fault that blew up the old ones.

                    Don't forget to set the impedance selector switch on the amp correctly (if it has one)
                    "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                    -David VanHorn

                    Comment


                      #50
                      Re: Sony STR-DB940 pulled back from the brink

                      Sorry for hijacking this thread.
                      I resoldered the relay joints, but actually my current problem lies somewhere else with this receiver.

                      I have a ground type humming from the SUB channel, using the SUB PRE OUT (the only sub out rca on this model). Its very notable, even if volume is turned completely down on the receiver.
                      Beside this problem, everything is working perfect. 2 channel / 5.1 sound playing, and so on.

                      Also, if I use the "selector" button on the front, theres loud "echo click" in the noise, present in the subwoofer.
                      Its clearly worst, when listening to a source with Dolby output (DD lightened in the display).

                      When removing the SUB RCA cable to eg. "Center Pre Out" or "Front L pre out" RCA, THERES NO PROBLEM. Only with the SUB PRE OUT.

                      Any advise where to look for dead caps or bad solder joints?

                      Comment


                        #51
                        Re: Sony STR-DB940 pulled back from the brink

                        Thanks for the pointers, peeps! My STR-DB940 would work fine for the first 5 to 10 minutes, but would then "click" and the front channels would just stop working.
                        I used Furball's and Ethan McF's images to solder the 16 legs.
                        I turned it over, opened up the bottom side. The solder joints didn't look bad at all, but I thought: "It's going to take 5 minutes, so it's worth a shot". (It took about 15 ).
                        Anyway, I must say, I really didn't think I knew what I was doing or that it was going to solve the problem, but I put a bit of tin on each of the legs (tried to get the tin solidify at the base of the legs as much as possible). And as it turns out, it works! I haven't had the front speakers fail on me yet, after a week. So again, thanks!

                        tl;dr: front speakers often stopped working, I put tin on the base of the 16 legs and it's been playing perfectly for over a week now.

                        Comment


                          #52
                          Re: Sony STR-DB940 pulled back from the brink--Mine TOO!!! Thankyou !!!!

                          Dear Furball,

                          I just wanted to tell you what a huge help you have been, I love this Receiver and the issue was multiple ticking and center channel intermittently dropping out cold, I was elated to have it back and working.


                          A Couple of pointers: I invited a friend who is an electronics engineer, and he did the soldering. What he taught me is to be very delicate with the soldering and that it doesn't matter if the points looked ok, because in the beginning he was reluctant to re-solder the points. Secondly, he used a bright reading lamp and a magnifying glass to solder. So a few beers later.. happy chappy I am ..again.. HUGE thanks for helping me repair and enjoy my STR-DB9-940-QS :-) hope to catch you one day for a beer!






                          Originally posted by Furball View Post
                          Result

                          4mins work with the soldering iron and job done, all points can be got at via the removeable panel underneath.
                          It took longer to disconnect and remove the amp from the AV rack than it did to solder up the relays

                          So far its been running for about 20mins and hasnt clicked or dropped a channel once so recon its cured, also the centre speaker output quality has improved by 50% at least, I just hadnt realised how bad it had got

                          Many thanks to Ethan and the others who have contributed and for anyone else with the same problem heres a pic of the underside of the amp with the relay points that need touching up in RED, the YELLOW dots are a set of connectors that I also touched up as they looked a bit rough.



                          I've also added it as an attachment just incase the host of the above drops out

                          Right time for a film I recon

                          Furball

                          Comment


                            #53
                            Re: Sony STR-DB940 pulled back from the brink

                            I've done the soldering steps before, and it did work out perfectly! Last Friday, I was cleaning my STR-DB940 (with an air compressor) and I resoldered the speaker terminals again because of strange sounds coming from the speakers when playing music. Now it flashes PROTECTION and does absolutely nothing (apart from turning on and off).

                            I tried to fix the solder pads by resoldering loads of different things, but the PROTECTION message didn't go away. Last night I noticed little electrical sparks at the solder points. They weren't jumping to another trace or solder point, but just at it's own connection. Could this be the issue?

                            For now, my receiver has been declared as broken

                            Thanks in advance,
                            Tim

                            Comment


                              #54
                              Re: Sony STR-DB940 pulled back from the brink

                              Hey chaps!

                              I did this process recently as one of my back channels was being horribly dodgy and since doing it the problem has been solved!

                              Thank you for this thread and even many years after it being posted, its still massively useful!

                              The channel volumes seem more consistent and balanced and (maybe its just psychosomatic) but the quality seems to have improved somewhat. The amp is definitely 'different' to how it was, but I can't quite put my finger on it. I'm so pleased with this fix because it was beautifully easy and has given a new lease of life to my ol' DB940. As my small contribution to give back to this community and thread as thanks for the wonderful fix, I've taken some nice higher resolution pictures of the board, and re-annotated them with the solder locations in a different colour to red as due to my colour-blindness I had a bit of trouble with. JPG compression doesn't do any favors to board-shots so I've uploaded it as a PNG instead.

                              Link for image here (which should hopefully work) plus full res attached to backup the free hoster.
                              Attached Files

                              Comment


                                #55
                                Re: Sony STR-DB940 pulled back from the brink

                                Oh that topic brings memories
                                I saved a sony str-db9X0qs ( the one with the "all golden nichicon caps" and the ugliest remote control ever ) from the dumpster.
                                The problem was that it was switching off when warm. It turned out to be cracked solder joints on the pre-amp ICs on the main board ( the heat-discolored sections on the pcbs from the above posts ). No issues with the relays tho. The word is this is the last good sony amp/receiver

                                Comment


                                  #56
                                  Re: Sony STR-DB940 pulled back from the brink

                                  Nice to see this thread still going, well 9 years on, however our trusty DB940 started going into "protector" mode when you switched it on

                                  Not always but enough to be a right old pain in the............

                                  So as I'd picked up another one for £20 about 5yrs ago as a spare which "apparently" had a duff motorised volume motor, which actually turned out to be just the pin broken on the remote door meaning it thought the door was open all the time I swapped it out a few weeks with this spare DB940.
                                  Todays weather gave me the chance to pull the other one apart and do some research, theres lots of stuff on the web regarding Sonys going into "protector" and in the main folks are replacing resistors and some of the power transistors.

                                  As mine would work some of the time I felt sure it was the dreaded return of the "dry solder joint" so as the "protector" fault always appeared to be around the big power transistors I thought it was worth just going along all 10 and give them a blast with the iron and reflow them all.

                                  5 mins later and RESULT amps back up and running again with no sign of any "protector" message at power on.

                                  So if you have this issue then I'd suggest going along all 10 power transistors and reflow them as the first port of call before you even start thinking about going further.

                                  Just need to swap it back over with the spare now.

                                  Wonder if it will be another 9yrs before I'll need to do anything else to this fantasic amp.

                                  Comment


                                    #57
                                    Re: Sony STR-DB940 pulled back from the brink

                                    Thanks for the picture and all of your information! This weekend I have pulled my STR DB940 apart and touched up the solder joints as mentioned. My relay is now quit again!

                                    Comment


                                      #58
                                      Re: Sony STR-DB940 pulled back from the brink

                                      Originally posted by Furball View Post
                                      Result

                                      4mins work with the soldering iron and job done, all points can be got at via the removeable panel underneath.
                                      It took longer to disconnect and remove the amp from the AV rack than it did to solder up the relays

                                      So far its been running for about 20mins and hasnt clicked or dropped a channel once so recon its cured, also the centre speaker output quality has improved by 50% at least, I just hadnt realised how bad it had got

                                      Many thanks to Ethan and the others who have contributed and for anyone else with the same problem heres a pic of the underside of the amp with the relay points that need touching up in RED, the YELLOW dots are a set of connectors that I also touched up as they looked a bit rough.



                                      I've also added it as an attachment just incase the host of the above drops out

                                      Right time for a film I recon

                                      Furball
                                      Excellent. Many thanks for your efforts. Sony STR-DB940 back from the grave. Warning: Turn the volume down before powering up right after the fix!

                                      Comment


                                        #59
                                        Re: Sony STR-DB940 pulled back from the brink

                                        Just wanted to say thanks to everyone for all their detailed updates here. I write this during the coronavirus lockdown. My amp had been the same and have been listening to spotify via my TV instead. Your updates inspired me to give it a go. I soldered the relays from beneath but unfortunately it didnt make a difference.
                                        In addition the amp won't power up now. There is a a relay thud when it is plugged in but the power button does nothing. I guess it will go in the parts bin (ebay) and I will be grateful the TV works, even though the sound is awful (its a 15 year old TV!)
                                        Thank you.

                                        Comment


                                          #60
                                          Re: Sony STR-DB940 pulled back from the brink

                                          Did you change the relays? Those go bad with age.

                                          Comment

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