Pioneer CDJ-400 - No Display On Powerup

[dazzler22]

I believe the amp is built in onto the board, could be wrong though. I'm not totally sure what i'm looking for, the schematic seems to suggest that it is on that board....

The DAC is on that board,

I have ordered a S/PDIF to Analogue converter just to test if the digital side is affected as well...

 

[(*steve*)]

OK, it just has a line level output. (I was expecting that it could drive speakers or headphones etc.)

If both channels are affected it is either IC107, the power supply to IC107 and/or the DAC, or the DAC itself.

I think I have listed them in order from most probable to least. There are some discrete components (see the top of page 50) but it's hard to imagine any affecting both channels.

Checking out the SPDIF output is not a bad idea.

 

[dazzler22]

I guess power supply to the IC107 is not a bad shout.. as this is also the 5v that was causing problems with the display, i wonder if i have missed some additional dodgy soldering somewhere and it is not getting the correct voltage from the main board...

on the plus side if it either of the chips at fault they are readily available at a low price... but i would guess it is going to be a power issue of some description...

 

[dazzler22]

Well there is nothing wrong with the pcb with the audio bit on it. I have swapped that pcb into another working cdj and it is fine.

I'm guessing the problem must lie with the main pcb or one of the cables leading to the board. The other possibility is that it is a problem with the board with the connectors on. That is next on the list to swap over and test..

I have also noticed that there is a capacitor missing on the main pcb. Right we there was some dodgy soldering there is ment to be a small capacitor. It is not there.... It sits between +5 and ground this I don't understand...

Number is c1159 not sure what that would do?

Cheers
Daz

 

[(*steve*)]

It sounds like you're comparing your dead unit with a good one -- great!

If you can give references into the service manual that would be great. You always seem to catch me when I'm limited to a mobile device.

 

[dazzler22]

ok so with further swapping of parts the problem is definitely on the main PCB still, as far as i can tell power is getting through ok to the other board (with the DAC and DSP) because of the way it all plugs together it is is difficult to test this live. continuity seems to check out, which means it could be a voltage issue?

im a little bit lost on what to test next now.... the missing cap is a worry but then there are a couple other places with them missing (they are capacitors between + and ground) apparently this is to remove noise??

the sound coming out is distorted almost as if it is peaking internally but yet also really quiet.....

very confused...

 

[dazzler22]

I think i might have found the problem...

the -5v is reading as .2v surly a multimeter should read this as -5v? im not sure what the -5 does? but it looks like the -5 converter is not working maybe?

do we think this could be the problem? or maybe my meter is not reading it right...

have added a pic of the underside of the power pcb, taken with my dslr, hopefully a bit better quality! see any issues here?

 

[(*steve*)]

It's a little unusual for -5V to measure as a positive voltage, but it may be due to the regulator being open circuit.

Apart from the diabolical hand soldering, nothing stands out. And even the poor soldering doesn't look to be a real issue.

I would be tracing the -5V back to the source to see where the problem is. Let me take another look at the manual...

 

[(*steve*)]

OK, so this is the regulator board "I" on page 19, and the power supply is "K".

First step is to confirm that the power supply is giving you +12V (which should be a formality) Note that both 12V lines and both gnd lines are shown as simply paralleled (see page 63).

Then check ALL the voltages from the REGB board (see page 21):

VFDP30 - 30V
V+5R6 - 5.6V
V+5 - 5V
V+3R3 - 3.3V
V+7M - 7V
V-5 - -5V <-- we know that one is bad.

The circuit diagram of the REGB board is on Page 60 and 61. Each of the rails is produced independently -- which is good, because we can expect that the failure of the -5V rail will be isolated to just the -5V rail.

The most likely failure is Q1904. Also suspect could be IC1901. The good news is that if it is this IC, then the datasheet is available, and so is the chip!

OK, Q1904 is a 2SA2092 (datasheet, availability) and appears to be a really piddly little transistor. If the -5V rail is too heavily loaded, I can see this emitting a puff of magic smoke very quickly. However, since transistors normally fail short circuit, I would expect that this has progressed to the next stage (exploding!) or that L1903 has failed. Another possibility is that there is some sort of fuse that is not shown in the schematic.

Most of these components are visible, and Q1904 clearly hasn't exploded.

Start by measuring the voltage between ground and both leads of L1903, and all three leads of Q1904.

Be very careful taking voltage readings from this board as the surface mount components are small and one slip of your multimeter probe could cause more problems...

 

[dazzler22]

Great thanks for the responce. I will get testing tomorrow.

I cannot believe how bad the soldering is. It looks like I have been at it already!

Will report back with results.

Cheers
Daz

 

[dazzler22]

Q1904 on the side with 2 inputs has 11.94v on one and 7.79v on the other. On the single pin side it is .1v

Should this not have 12v and 0 or am I reading the diagram wrong?

As for
VFDP30 - 29.9v
V+5R6 - 5.58V
V+5 - 5V
V+3R3 - 3.4V
V+7M - 7V
V-5 - -.1v

does this mean that Q1904 is in need of replacement? Do we think the issue with the -5v and sound quality are related?

Cheers
Daz

 

[(*steve*)]

As for
VFDP30 - 29.9v
V+5R6 - 5.58V
V+5 - 5V
V+3R3 - 3.4V
V+7M - 7V
V-5 - -.1v

This confirms it's just the -5V power supply -- good.

Q1904 on the side with 2 inputs has 11.94v on one and 7.79v on the other. On the single pin side it is .1v

Should this not have 12v and 0 or am I reading the diagram wrong?

does this mean that Q1904 is in need of replacement? Do we think the issue with the -5v and sound quality are related?

I'm not exactly sure where you're measuring these. Can you show me the points on the PCB where you measure the voltage and what you get.

edit: Oh, and also measure the 12V rail from the power supply. Is it 11.94V?

 

[dazzler22]

have added a pic of the marked PCB with where i took the measurements,

i believe that the 12v rails are running at 11.94 but will double check soon as i get home.

Cheers
Daz

 

[dazzler22]

The 12v rails are at 11.97v

The pin on Q1904 is at 11.94v....

Any ideas on that?

The ic is Soo tiny I'm not sure I can test it with my multimeter without shorting it out... There is no way I could solder it with my gear I don't think.. but hey there is always a maybe Q1904 I Could do easy enough I think!

Any tips for soldering stuff that small if I have too?

Cheers
Daz

 

[(*steve*)]

Those voltages are interesting. I'll have to have a serious think and get back to you.

Those transistors look small, but they're pretty easily hand soldered. If it comes to that I will give you some hints.

 

[dazzler22]

7.74v is weird i'm guessing as that does not make a lot of sense....

as for the 11.94v im guessing that means there is a little bit being lost somewhere?

as ever i really appreciate the help on this!

Cheers
Daz

 

[(*steve*)]

Yep, 11.94 Vs 11.97 can be accounted for by 1A flowing through a 0.03 ohm resistance. A length of PCB track will have that.

You're right, the 7.79 volts is interesting because that point should not get below about 11.3V. This suggests to me that this transistor is toast.

However, before we come to that final conclusion, place your meter on it's diode check range (or resistance range if you don't have a diode test range), and with the power off, and the red probe on the point which measured 7.79V, and the black probe on the one which measured 11.94, tell me what you see (and the range it's on)

Then reverse the probes and try again.

Just to give these point their proper names... 11.94 is the emitter (E), 0.1V is the collector (C), and 7.79 is the base (B).

I have asked you to give me readings both ways across B and E.

It would also be useful to get the readings (again, both ways) across B and C, and C and E

The best way to give me the results is in a table:

Diode test/resistance range (specify)

Black B, Red E reading
Red E, Black B reading
Black B, Red C reading
Red C, Black B reading
Black C, Red E reading
Red E, Black C reading​

 

[dazzler22]

Great i will do this soon as i get home, (at work at the mo). I believe that my multimeter has a Diode test range. (under resistance on the 20 scale it has a picture of a diode symbol)

Thanks
Daz

 

[dazzler22]

I just noticed I also had a reply on this from diyaudio and someone has pointed out that the music output would be tinny and quiet if the mute circuit was active, the mute circuit looks like it needs -5v

I guess this would tie up with why the audio output is messed alongside the issue of the missing -5v.

will get you the test values soon as i get home.

Cheers
Daz

 

[dazzler22]

ok the test results are in, this is with my multimeter set to diode test and the range is 2K



Black B, Red E reading = .492
Red B, Black E reading = .502
Black B, Red C reading = .561
Red B, Black C reading = .886
Black C, Red E reading = .411
Red C, Black E reading = .121

I have had a external DAC finally arrive so im gonna rebuild the beast and check that shortly, if it is indeed the mute circuit that is gone then the external DAC should make it usable using the digital out.

let me know what the above means.

Cheers
Daz