No signal into DJ mixer - Need help locating PCB with problem

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wayneh

Joined Sep 9, 2010
17,153
Consider using a pin to reach into those tight connections. It'll save a lot of time tracing and errors due to that difficult chore. Just be careful that whatever tool you use doesn't cause inadvertent connections or shorts. Doo doo happens.
 

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mynamesalex

Joined Oct 4, 2012
53
OKAY. Progress has been made today. I just got done testing some voltages on the CN201 connector and all seems to be in order on that end. I tested on the main rails and got the following:
v+5D = 5.01
V+8V = 8.39-8.40
V3R3 = 3.24

The readings weren't far off from what they were supposed to be so I'm assuming that's fine? Any ideas as to where I should test from here. I'm just going to begin testing various points from the schematics on each board to make sure they're getting power. If anyone could be of further assistance please feel free to help! Thanks.

Edit: I attached a picture of the overall board view. I can take closer, more detailed pictures if needed. The connector I tested is on the bottom right next to the PSU. It is white and has black wires with one white coming out of it. Also note that there is another board under the one on the top.
 

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mynamesalex

Joined Oct 4, 2012
53
Alright so I actually may have found a problem. If someone can take a look at page 84 of the service manual, you'll see CN904 at the top of the board diagram. The rails you can test coming out of that are V+15, V- 15 and V+5A. The positive V+15 value was not what it should be. Where should I progress from here? The following were the recorded values I got.

V+15 = -.889
V+5A = 5.01
V-15 = -14.69

Thanks!
 
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MrChips

Joined Oct 2, 2009
24,205
Consider that good news!
Good that you have found something. I will look at the schematics and get back unless someone else can provide some suggestions.
 

Thread Starter

mynamesalex

Joined Oct 4, 2012
53
Consider that good news!
Good that you have found something. I will look at the schematics and get back unless someone else can provide some suggestions.
Thanks! I feel like I'm already learning so much from this hahaha. I'm having fun while doing it too! Quick correction to note, though. The value that was off was actually negative .889 and not positive. I'll edit it on my post as well.
 

MrChips

Joined Oct 2, 2009
24,205
There is also +12V supply. Check that also. I suspect you will find that is low also since it is derived from the +15V supply.

There are two possibilities.

1) The +15V supply is bad.
2) Something is shorting the +15V supply.

The +15V supply begins on page 71, CN202 and CN203, and supplies 0.5A

The most common fault is a capacitor across the +15V supply chain is shorting.
You can follow the supply chain by looking at the following connectors:

page 29, CN455, CN456
page 31, CN1501, CN1502
page 59, CN903, CN904
page 66, CN2502
page 71, CN202, CN203

Assume that the short is on one of the boards. See if you can disconnect boards until the +15V comes up to normal.
 

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mynamesalex

Joined Oct 4, 2012
53
There is also +12V supply. Check that also. I suspect you will find that is low also since it is derived from the +15V supply.

There are two possibilities.

1) The +15V supply is bad.
2) Something is shorting the +15V supply.

The +15V supply begins on page 71, CN202 and CN203, and supplies 0.5A

The most common fault is a capacitor across the +15V supply chain is shorting.
You can follow the supply chain by looking at the following connectors:

page 29, CN455, CN456
page 31, CN1501, CN1502
page 59, CN903, CN904
page 66, CN2502
page 71, CN202, CN203

Assume that the short is on one of the boards. See if you can disconnect boards until the +15V comes up to normal.
Great. You were right about the +12V connector. It was hiding behind something and came up to be about -.363V. Now am I just finding those connectors you listed and testing something or am I going to disconnect them one by one and test?
 

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mynamesalex

Joined Oct 4, 2012
53
You will disconnect one at a time and test the +15V supply line closest to the supply, i.e. at CN202 or CN203.
With all connected, I am getting a 15.08V reading at the +15V at CN202. I was getting a fairly normal reading at CN203 also. Keep in mind that the +15V that I tested earlier was the connection with the problem. It was CN904 connector. Sorry if I'm misunderstanding this a bit. :/
 

Thread Starter

mynamesalex

Joined Oct 4, 2012
53
Just double checked the connectors at CN202 and CN203 and getting 15.06V at the CN203 +15V connector and 15.09V at the +15V CN202 connector. I would think the problem would be related to the board that the CN202 connector is on as that is the board that is supplying the 15V to the CN904 connector, yes?
 

MrChips

Joined Oct 2, 2009
24,205
Make sure you are measuring at the connectors correctly.

CN202 and CN903
1 +15V
2 +5V
3 GND
4 -15V
5 GND

CN904
1 +5V
2 GND
3 +15V
4 GND
5 -15V
6 +12V

There are no electronic components between CN202, CN903 and CN904.
If there is no +15V at CN904 then there is a loose connector or a broken wire or connection.
Examine visually very carefully.
 

Thread Starter

mynamesalex

Joined Oct 4, 2012
53
Make sure you are measuring at the connectors correctly.

CN202 and CN903
1 +15V
2 +5V
3 GND
4 -15V
5 GND

CN904
1 +5V
2 GND
3 +15V
4 GND
5 -15V
6 +12V

There are no electronic components between CN202, CN903 and CN904.
If there is no +15V at CN904 then there is a loose connector or a broken wire or connection.
Examine visually very carefully.
I attached pictures to this post. Picture 01 is a view of the CN904 connector. It is on a board above the CN203 and CN903 connector. The CN904 connector is COMING from the board below. It is not direct from the PSU. In picture 02 you have a view of the board discussed that was underneath the CN904 connector. The cable with the orange is coming direct from the PSU and is labeled CN903. This cable is getting the +15V fine. The cable to the left of that is where the CN904 cable is coming from. Now, my question is in regards to how you addressed CN202 and CN904. I'm seeing that as ONE cable/connector. Are you wanting me to test the holes in the cable? I've been testing test points on the board which you can see in the pictures. They are labeled V+15, V-15, etcetc. What is the difference between CN202 and CN904? I will triple check the voltages but they remain the same at the test points from what I previously posted. Thanks again chips. You're being a ton of help. I appreciate it.

EDIT: Also note that when all ribbon cables and such are unplugged from the board that CN904 is on, the V+15 voltage is about -1.794V. I don't know if that means anything but hopefully someone can clarify. Thanks.
 

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MrChips

Joined Oct 2, 2009
24,205
Just to double check, I am using page 105 as my reference.

Looking at CN904 and CN903 at the right bottom corner of the diagram.

What is the voltage at CN903 pin-1?

What is the voltage at CN904 pin-3?

They both should be +15V.
 

sheldons

Joined Oct 26, 2011
613
looked at your service manual at the circuit around that connector C904-what you need to check is Ic1167-it is most probably open circuit and as it is a fuse it needs to be replaced with the correct type-you could temporarily connect a 1 ohm fusible resistor in place of it -if it burns and goes oc on power up you need to find where the short is on that supply rail...you arent far away from the failed component-may even be a sc capacitor after that fuse on that supply rail
 

Thread Starter

mynamesalex

Joined Oct 4, 2012
53
I see IC1167 labeled on the board but not exactly sure where to look for the fuse. Is there a way for me to test to see if it is open? Where should I test from here?
 

MrChips

Joined Oct 2, 2009
24,205
There is no IC1167, IC1168 or IC1169 shown in the photo posted by the op.

I still would like to know the voltages at CN903 and CN904.
This is a direct trace from CN903 pin-1 to CN904 pin-3 and should read +15V.
 

Thread Starter

mynamesalex

Joined Oct 4, 2012
53
There is no IC1167, IC1168 or IC1169 shown in the photo posted by the op.

I still would like to know the voltages at CN903 and CN904.
This is a direct trace from CN903 pin-1 to CN904 pin-3 and should read +15V.
When you say test the specific pins, am I testing the pins within the cables to check the voltages? I've been testing the test points on the board where the voltages are labeled. Sorry for confusion. I ask because the pins on the cable are very small and I wouldn't be able to get the multimeter lead into them without something else.
 
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Thread Starter

mynamesalex

Joined Oct 4, 2012
53
Okay so I tested the pins on the CN904 connector and actually got one strange reading yet the +15V was correct. I got the following:

1. V+5 = +5.04V
2. GND = -0V
3. V+15 = +15.10V
4. GND = -0V
5. V-15 = -14.71V
6. V+12 = +4.5MV

I'm assuming pin 6 shouldn't be that voltage.. I'll check the supply coming from the PSU now.
 

MrChips

Joined Oct 2, 2009
24,205
Someone suggested awhile back to use single stranded hookup wire to use as a fine probe to get at the pins on the connector.

It is important to make your tests carefully otherwise we will be on a wild goose chase (which we already are on).
 
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