Hello all.
If the thread does not belong here, please move it to what is more suitable. I have had such positive experiences with the help from diyAudio before so I wanted to check here, the level of professionalism is a whole lot higher than on other forums.
So, I am repairing this DJM-700 DJ mixer for a friend, who gave it to me and said that the channel faders were glitchy and not behaving right. Sure enough, looking inside there was a little bit of drink spillage that had gotten into to half of the faders' housings. Luckily the spill area did not cover a lot, only these faders and one push-button had been affected. So I ordered new parts from eBay and replaced all 4x channel faders (as well as that one cue button), and they are again working fine!
There had been some minor spills onto the upside of the PCB board, only in-between components, no corrosion on the parts nor the traces. I easily cleaned that off, and I must say that the boards look nice to the naked eye.
Thinking I was done with the repair, I put everything together, but when testing it out, there is no response from a number of buttons to the right of the mixer. I have attached an image to make things easier. There is no response when pushing the "MASTER" cue button, and the same goes for the "EFFECTS" cue, as well as the small "FILTER" button which activates or deactivates the frequency filter next to it. The "TAP" button for tapping in a BPM, works fine during testing - but the beat quantizer arrows also seem unresponsive (Though for these I am not sure if I need to have something playing for them to work).
The buttons do click properly, but don't light up at all. Unluckily, I cannot remember whether they worked or not before I begun the repair.
I would prefer to try and fix them myself as I've come this far by now, is there anyone here on the forums who might have an idea what parts of the mixer to be looking for potential faults? Perhaps someone is better than me at reading schematics, so I will attach the service manual below as well.
Thanks a lot and enjoy your Sunday!
A
If the thread does not belong here, please move it to what is more suitable. I have had such positive experiences with the help from diyAudio before so I wanted to check here, the level of professionalism is a whole lot higher than on other forums.
So, I am repairing this DJM-700 DJ mixer for a friend, who gave it to me and said that the channel faders were glitchy and not behaving right. Sure enough, looking inside there was a little bit of drink spillage that had gotten into to half of the faders' housings. Luckily the spill area did not cover a lot, only these faders and one push-button had been affected. So I ordered new parts from eBay and replaced all 4x channel faders (as well as that one cue button), and they are again working fine!
There had been some minor spills onto the upside of the PCB board, only in-between components, no corrosion on the parts nor the traces. I easily cleaned that off, and I must say that the boards look nice to the naked eye.
Thinking I was done with the repair, I put everything together, but when testing it out, there is no response from a number of buttons to the right of the mixer. I have attached an image to make things easier. There is no response when pushing the "MASTER" cue button, and the same goes for the "EFFECTS" cue, as well as the small "FILTER" button which activates or deactivates the frequency filter next to it. The "TAP" button for tapping in a BPM, works fine during testing - but the beat quantizer arrows also seem unresponsive (Though for these I am not sure if I need to have something playing for them to work).
The buttons do click properly, but don't light up at all. Unluckily, I cannot remember whether they worked or not before I begun the repair.
I would prefer to try and fix them myself as I've come this far by now, is there anyone here on the forums who might have an idea what parts of the mixer to be looking for potential faults? Perhaps someone is better than me at reading schematics, so I will attach the service manual below as well.
Thanks a lot and enjoy your Sunday!
A
Attachments
I own the DJM800.
Have You Ohmed the switches ? Usually broken tactile switches click correctly but don't make contact.
Check if the flat cables / connectors are properly seated and their solder pads.
I'm gonna check all of them, I just assumed they would be fine because there were no visual defects around them and they clicked fine. All the flat cables seem properly seated, I'm gonna check them one by one and also their solder.
Sometimes dropping a blob of contact cleaner on the switch and let it soak helps. Solder two wires to the switch contacts and touch them. If the mixer reacts, the switch is faulty, or You'll have to follow the schematic and ohm the board to check if there is continuity between the switch and the microprocessor pins.
Have you had any luck with Test Mode, page 22 of the service manual PDF? It looks like Modes 4 and 5 might be useful for these symptoms.
Also, but not specific to this unit, the sockets that receive the pressure-fit flat-conductor ribbon cables are notorious for attracting and concealing spills. If the liquid gets anywhere near one, capillary action sucks it in between the PCB and back of the socket. A good overnight, un-powered soak in de-ionized water may remedy it. Then dry it thoroughly before applying power.
If it's a dirty switch problem, I've never found anything better than Cramolin, though I'm not sure whether it's still available.
Cheers
Also, but not specific to this unit, the sockets that receive the pressure-fit flat-conductor ribbon cables are notorious for attracting and concealing spills. If the liquid gets anywhere near one, capillary action sucks it in between the PCB and back of the socket. A good overnight, un-powered soak in de-ionized water may remedy it. Then dry it thoroughly before applying power.
If it's a dirty switch problem, I've never found anything better than Cramolin, though I'm not sure whether it's still available.
Cheers
Yes I read briefly about the test-mode, might come in handy later. As for now, I did solder extension wires as suggested above to determine whether the buttons are faulty or not, and I actually got the Master and Effect cue to work when holding each pair of wire ends together - so that is good news.
As for the Filter On/Off button though, the wire test did not seem to have an effect. It should go from steady light to a pulsating light when activated, as seen in this video around the 1-minute mark: Pioneer DJM-700 Demo Video All Effects
Maybe I should do an audio-test to see if it works... Or maybe I am missing something on how the mixer actually works, not a Pioneer user myself.
Will do cable test on the other faulty buttons now.
/ A
As for the Filter On/Off button though, the wire test did not seem to have an effect. It should go from steady light to a pulsating light when activated, as seen in this video around the 1-minute mark: Pioneer DJM-700 Demo Video All Effects
Maybe I should do an audio-test to see if it works... Or maybe I am missing something on how the mixer actually works, not a Pioneer user myself.
Will do cable test on the other faulty buttons now.
/ A
I have done some more testing and there are indeed several tactile switches that need replacements, since triggering with test cables does the trick. That's the good news. However, there are three buttons arranged here in the row in the picture, where bridging the connection with test cables does not do anything. Sigh... Guessing there is some fault further up the line then. Anyone good at reading schematics perhaps could give me some help?
The buttons in question are the: the left BPM quantizer (which divides the effect's tempo), the switch to change from manual BPM detection to Auto, and finally the Filter ON/OFF button.
I will try my best to have a further look, but any help is appreciated.
Arvid
The buttons in question are the: the left BPM quantizer (which divides the effect's tempo), the switch to change from manual BPM detection to Auto, and finally the Filter ON/OFF button.
I will try my best to have a further look, but any help is appreciated.
Arvid
Could you give the component designation of those 3 switches?
I'm studying the board prints trying to identify them and having little luck.
Thanks
Rick
I'm studying the board prints trying to identify them and having little luck.
Thanks
Rick
Due to the time, I actually accepted defeat and handed the mixer in for service now - I might have done it on my own, but I did not want to hold up the mixer for too long - with my somewhat limited knowledge regarding IC's etc., I feel it was the right decision.
Anyways, appreciate all the help here. Perhaps the thread comes in use for someone else.
Anyways, appreciate all the help here. Perhaps the thread comes in use for someone else.
Sorry to hear that . .
The scan strobe C5 is responsible for those 3 switches; it comes from pin 62 of IC1101, the SUB CPU, page 72, but it has to make it through 4 large-pin-count connectors to get there.
C5 also drives the column of LED's comprising MASTER L (sheet 'E' page 78), and provides the strobe for CRFD ASSIGN CH1 (sheet 'F', page 81). SUB CPU IC1101 monitors the latter via R18 and R19, pins 77 and 78. Unless MASTER L is dark, C5 is being asserted (driven High), and is getting to sheet 'E'.
The original unhappy switches S5010, S5012 and S5016 have another uniqueness -- due to a quirk of design/layout, the detection of those 3 switches (row lines R15, R17, and R16 respectively) are on a separate corner of IC1101 all to themselves -- pins 3, 1 and 2 respectively.
The reason we pay close attention to the physical arrangement of these signals is the nature of a spill. A few drops of dried-up soft drink or hot cocoa is all it takes to heavily load such high-impedance lines -- the pull-down resistors on the 'Rxx' lines are 100k. It doesn't take much! 😉
Sad Regards,
Rick
The scan strobe C5 is responsible for those 3 switches; it comes from pin 62 of IC1101, the SUB CPU, page 72, but it has to make it through 4 large-pin-count connectors to get there.
C5 also drives the column of LED's comprising MASTER L (sheet 'E' page 78), and provides the strobe for CRFD ASSIGN CH1 (sheet 'F', page 81). SUB CPU IC1101 monitors the latter via R18 and R19, pins 77 and 78. Unless MASTER L is dark, C5 is being asserted (driven High), and is getting to sheet 'E'.
The original unhappy switches S5010, S5012 and S5016 have another uniqueness -- due to a quirk of design/layout, the detection of those 3 switches (row lines R15, R17, and R16 respectively) are on a separate corner of IC1101 all to themselves -- pins 3, 1 and 2 respectively.
The reason we pay close attention to the physical arrangement of these signals is the nature of a spill. A few drops of dried-up soft drink or hot cocoa is all it takes to heavily load such high-impedance lines -- the pull-down resistors on the 'Rxx' lines are 100k. It doesn't take much! 😉
Sad Regards,
Rick
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That's really great info. Yes exactly, the left arrangement of Master Out-diods would not light up either (although the sound out is clearly in stereo), so what you wrote makes sense. Shame, now I wished I hadn't handed it in, but it is what it is.
So I would have had to check the resistors on the outbound lines from the CPU, then? Or a possibility that the actual CPU is at fault?
Best,
A
So I would have had to check the resistors on the outbound lines from the CPU, then? Or a possibility that the actual CPU is at fault?
Best,
A
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I would work both ends to the middle, generally. Since we followed C5 back to IC1101 pin 62 on the schematic, confirm it there. Next check for it at the first connector where it enters the board -- CN5001, sheet E, page 78, wasn't it? Continue in that manner 'til you find the connector with the loose socket, cracked wire at the entry, hairline board crack, or resistor or 0-ohm jumper where it stops. Surface mount parts can capture a droplet and by capillary action make it disappear underneath. Then over a few days or weeks corrosion has its way with the connection. Same with most connector types.
Odds are still better that it's not the CPU, though.
Don't let me make you feel bad about throwing in the towel -- fortunately there are folks better than me at making such decisions -- makes for a better world.
Cheers
Odds are still better that it's not the CPU, though.
Don't let me make you feel bad about throwing in the towel -- fortunately there are folks better than me at making such decisions -- makes for a better world.
Cheers