DM4800 Phantom Power Kaput

DaveDC9

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DM 4800
Morning Everyone,
Haven't been here for a while even though I've been a member since 2014. My DM4800 has been performing well over the last 13 years although I did have to replace the LCD menu screen like many here. You guys were invaluable for doing that of which I was greatly appreciative!!
The problem I'm having now is with the 48v phantom power supply. It has failed across all channels. I was experiencing a "pop" of sorts through input #16 where I have my Polytone guitar amp mic'ed (AKG C414) and set up with Comp, EQ, effects etc.........At first I thought it was the house electrical system just fluctuating and causing my amp to litely pop every now and then. I do have my entire recording setup on a battery backup in case of electrical failure so I can get everything shutdown in an orderly manner if that happens but the amp isn't on it. I checked the amp, mic cable, mic, phantom power switch, trim pot etc.... I checked everything I could think of. The problem was intermittent and would go away for a while. The other day I sat down to play at bit while I watch my financial shows and the phantom power was completely gone. Nothing. Took the 414 and plugged it into the other inputs and pp to no avail. Plugged a dynamic mic in and the channel inputs all work fine so I'm at a loss here. To get an idea of what I could possibly be looking at I found a PCB board on eBay that appears to be one of the 3 boards making up the input section. I only recognized it because of the switch configuration with 2 phantom power switches for the 8 inputs. I've included a picture for reference. Looks like it would be pretty straight forward to replace. If the problem originates in the board. But, I'm thinking that if it was just one board that all 3 boards wouldn't go out at once so this leads me to believe the problem is upstream from the PCB boards. Is there a central thingamajig that is the main 48v power that provides the power to which ever input and pp switch is activated? I don't know.

Has anyone here had a problem with the phantom power on your 3200 or 4800? I can work around this problem with Presonus EUREKA preamp I have as it has 48v power, EQ, Comp and I can just run it into the line input of the 4800 but, I would prefer to use the input of the 4800 itself. I sure would appreciate some help from you guys that pop the hood on these things and are knowledgeable of what your looking at. If anyone can shed some light on this for me I would greatly appreciate the help. I love this board as it is the center of my recording setup and come hell or high water, I'm gonna fix it, have it fixed or something. Here is a picture of the board.
Thanks in advance fellas for any help you can afford me!!
DaveDC9
 

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Hello, first of all, before swapping/removing any card is to check the +48V.
1) If you do not have phantom power supply on any of the 16 channel It is certainly the power supply... or connection (why not) (voltmeter between 2 and 1).
2) Check it at the Power supply or at INPUT AMP PCB before the switch. If +48V is there, probleme of switch or connectors, If 48V is missing, it is at the POWER supply stage. If you do not have phantom power supply on any of the 16 channel It is certainly the power supply... or connection (why not).
 
Hello QUEVAL!!
I found some pictures with the top of the console removed showing the mic/line/48v section exposed. Had a fellow I contacted tell me to remove the ribbon cables and re-seat them. One at a time. But, like you, I'm thinking if the 48v failed on all three boards that it would indeed be the main power supply for all 3 PCB boards.
I don't have a volt meter and I've never used one but I'll go buy one and learn how to use it. Is the 48v power supply on each PCB board or does it sit somewhere else? Perhaps over on the left side of this picture underneath the Main Control Room monitor pot? Right side if you were facing the board? Can you show me on this picture where I should test this thing when I do get the volt meter?
Thank you sir for replying!!!
 

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Hi, Dave, I will take a look at the schema and will propose you where to check the +48V.
First Info:
The +48V came from main SW power supply, then goes to POWER SUB PCB (1 wire) then go to the 2 following PCB: INPUT AD DM (1), INPUT AD DM (9). Each PCB 1..8 and 9..16 connected to INPUT AMP DM.
Seems tha the schema of the SW Power supply are not included in the DM-3200 Scheamatic diagram.
Never the less, get a Voltmeter not difficult to use to measure voltage. I will propose you the best location to measure the +48V.
Cheers. Hervé
 
Thank you Herve', I'm going to go pick up a volt meter. I think I'm looking at a "auto ranging" model to measure for anything between the lowest and highest reading of which 48v should fall within. Was looking at the DM3200 part 2 document I got off the forum. Page 23 "Audio Block Diagram" where it shows the Mic/line schematic. It shows the XLR pins 1,2,3 and the line going to that Phantom/4ch relay going out (+48)...................wouldn't the 48v power also come in through that same relay as the XLR jack wouldn't generate the 48v power itself would it? That 48v output ^ goes somewhere. LOL!!! I'll check back when I return.
Here's a screen shot of the diagram I'm looking at.
Thank you!!!
 

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In fact the 48V came from Input AMP. See picture here enclosed connector P7 Pin 5 ( left)
Must have 48V bettween this pin (Red wire of voltmeter) and chassis metal part (Black wire 0V.
If not the case, check

You have to down load the "Service manual" DM-3200_RevD.pdf and the schema: for DM-3200 and the schematics DM-3200_SCH.pdf.
I did not remember where I found them.
I can provide them if needed.
 

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Hi Herve, downloaded the 4800 SM. Can you tell me which page depicts what you're talking about? Also, on the picture, resolution is not clear enough to locate the P7 pin 5 etc....... Is this in the area on the left side of the picture and above the main stereo outs are? That PCB board?
 
Top left of the board you have a connector. This is connector P7. This is a 5 pin connector. Pin 1, red, is on the right, pin 5 is on the left. Pin 5 must be at 48V.

Looking at the Schematics, go to the end of DM-4800_SCH.pdf, you will found a shematic diagram of the DM-4800 and you will find all board connections.

same file, go to PCB Input AMP, page 1/4, first page for this PCB bottom left, you will find P7 and the 48V input on pin 7.

Hop it will help you.
 
Is this the page that you are referring to in the DM4800 SCH. It's page 73. Upper right hand corner shows PCB Input Amp Dm (1), PCB Input Amp DM (9) and PCB Input Amp DM (17)


"Top left of the board you have a connector. This is connector P7. This is a 5 pin connector. Pin 1, red, is on the right, pin 5 is on the left. Pin 5 must be at 48V".

I apologize for this Herve, are you talking about this photo which is actually the top right area of the board but in the picture, it is upside down and reversed. It would be the top left as you're looking at the pict. I don't see a 5 pin connector here. Man, how you understand all of this is incredible!!! Appreciate your patience!!
 

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LOL..............Is this the board. I see a 5 pin connector right at the bottom, center?
 

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