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

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MrChips

Joined Oct 2, 2009
24,178
What is the lowest value resistor you have on hand if any at all?

If I had a 5 to 10Ω resistor I would use that across the blown fuse and see if the DJ mixer comes to life.
 

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mynamesalex

Joined Oct 4, 2012
53
I ordered two fuses. How many should I grab? & I have two different resistors on hand laying around. I'm not entirely sure what their values are though.. I think I may have one lower value one. It has two yellow bands, a silver or gray band and then a red band. Any way for me to tell what ohm resistor that is? & if I find a 5-10 ohm resistor, how would I attach it across the fuse?

Edit: I'll just grab a couple 5 ohm resistors from radioshack tomorrow morning. Just let me know how to attach them across the fuse.
 
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MrChips

Joined Oct 2, 2009
24,178
With the POWER OFF, take a 5Ω resistor and solder it between pin-3 of CN455 and the point on the PCB labeled V+15.

Turn the power on and see if the DJ mixer comes to life.

Monitor the voltage from V+15 to ground while you're at it.

 

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mynamesalex

Joined Oct 4, 2012
53
With the POWER OFF, take a 5Ω resistor and solder it between pin-3 of CN455 and the point on the PCB labeled V+15.

Turn the power on and see if the DJ mixer comes to life.

Monitor the voltage from V+15 to ground while you're at it.

Will do. I can just solder one end of the resistor directly onto that pin lead you're pointing to and also directly onto the 15V test point?
 

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mynamesalex

Joined Oct 4, 2012
53
Actually, I thought I had 5 ohm resistors as well but it turns out I only have 10 ohm. Would it be okay to use the 10 ohm or should I use two in parallel?
 

Thread Starter

mynamesalex

Joined Oct 4, 2012
53
Managed to solder that up and got about 13.90V at the 15V point and I also tested the 12V rail and got 11.50V or so. Seems that was fixed yet still no signs of life from the levels on the front of the board. I'm not sure if it would make a difference or not but there is a separate plate that goes over the PCB I'm doing work on that has the gain knobs on it. The knobs are mounted in the metal plate and have small PCB's that slide into connectors on the board i'm working on. I'm wondering if the board needs to be present in order for the levels to appear. Keep in mind I did test this in the beginning and was still receiving nothing.
 

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mynamesalex

Joined Oct 4, 2012
53
Thankfully you have a finish Assistance Guide with schematics. The bad information is this is electronically managed. Don't get your desires too great as yet.
What? I managed to fix it with everyones help. I'm just waiting for the fuse to come for replacement.
 

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mynamesalex

Joined Oct 4, 2012
53
That's good. Hopefully you will get the chance to use it a few more times in the near future.

We need to measure the current through the blown fuse to see if it is excessive.
Switch the DMM to the 10A range
Connect the RED lead in the upper jack that is labeled 10ADC.
Connect the BLACK lead to the bottom jack labeled COM.

With the DJ mixer plugged in and power on, connect the two leads at the points labeled 1 and 2.
Measure the current.

You will need a new fuse.

Here is an example of an SMD fuse:

http://www.digikey.com/product-detail/en/ERB-RD0R75X/P15121CT-ND/2796800

If you cannot get an SMD fuse an axial thru-hole fuse will do if you bend the leads to fit the SMD footprint:

http://www.digikey.com/product-detail/en/0251.750MAT1L/F5522CT-ND/3306912

Let's find out if there's anything wrong with the circuit first.
Can someone please point me towards the correct SMD fuse to buy? I purchased the above SMD fuse and it was definitely incorrect as I could barely see it. Maybe the size was off.
 

Thread Starter

mynamesalex

Joined Oct 4, 2012
53
Just wanted to let everyone know that this project has been completed! I wound up getting the correct fuse size from littelfuse and got it soldered on in place of the blown fuse. Thanks for all your help, seriously. You guys are awesome. I've learned a lot through this whole thing and I really am grateful. I appreciate the time and energy you put into helping people on this forum and trust me it doesn't go unnoticed.
 

wayneh

Joined Sep 9, 2010
17,153
Congrats. I honestly didn't think you had much chance at first but your persistence paid off, and everyone likes to see that. Thanks for the follow-up.
 
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