No m/l Input every 3-4 channels

[SoulStick]

Hi,

I'm a proud new owner of a dm4800. Very pleased with the console.
I've got everything up and running for the remote and patch.

My problem is on every 3to4 channel (3-4, 7-8, 11-12, etc) I have no inputsignal.
Everything is patched accordingly to the manual. But no sound from any of these channels.

Is there something I've missed? Or is there inputboard error?

Hope to solve the problem with your help.

Thx in advance,
Erik

 

[mixerizer]

Hi Erik - any progress?

if not, which sets of inputs are assigned to all of those channels? I see u r using the analog inputs, is the line switch set appropriately? I’m sure u can figure it out, maybe u can post some screen shots of your DM routing etc using the DMCompanion screen shot function?

Also, have you done a factory reset or run the diagnostics? There is a document around here detailing the process of holding keys down to reboot and either run diagnostics, update firmware or restore Factory settings.

 

[SoulStick]

Hi Micki,

I've routed every analog in to the according input channel (1to1)
The switch is selected to line. So far everything the same as the channels 1-2, 5-6, etc.

I've run the diagnostics and came out clean. No problems there.

I've made a screenshot of the TMCompanion.
When I start the DM within a minute I'm getting this input noise (only hiss) on the specific channels. See image

I'm thinking there's something wrong with the preamps in the DM.

I've studied the blockschematics and the signal of 1 and 2 (5-6, etc) is being processed differently then 3 and (7-8, etc).
So maybe I need to open up the DM for a little operation

The image of TM companion

 

[mixerizer]

Agreed, the fact that u see them only on the first 3 banks of inputs, where m/l inputs are usually assigned, makes me think it’s in the inputs, gain potentiometer etc. Sounds like you have done a lot to narrow it down to the inputs. It’s just odd that it’s just on 4/8, 12/16 and 20/24. Last q - Are u sure it isn’t the oscillator? I don’t know if it could be inserted but perhaps.

A few other things - what do you see on the meters when you route those m/l inputs to other mixer channels, either adjacent etc or random, or in the next layer, such as 25-48? Does the noise go to whatever channel to which the input is assigned?

im no expert in opening these up, but yes, you can very well see if cleaning and deoxing and or spot fixing them helps. Good luck!

 

[mixerizer]

and it’s interesting that the sound takes a minute to begin - perhaps it’s a capacitor or other component that has failed it’s spec and can be replaced.

 

[SoulStick]

Very good suggestion about the capacitor. It needs time to load/fill up indeed. So Maybe I'll have to check those.

It's not the oscillator because it's only routable to the busses and auxes. So if it's the oscillator there a whole other problem going on

When I route the channels to another layer (say 25) the same input noise is coming up.
But no input signal. When I gain the channel to max. the overload led is blinking, so there is signal.

I think there's something (like a capacitor) on the master AD or master amp going on.
I'm putting on my surgery clothes and divin' into the DM.

Keep you posted

 

[Arjan P]

Hi Micki,
I've studied the blockschematics and the signal of 1 and 2 (5-6, etc) is being processed differently then 3 and (7-8, etc).So maybe I need to open up the DM for a little operation

I cannot agree with you there - or we are looking at different block diagrams? The one from the DM-4800 shows 'Mic/Line 1-24' inputs as identical, then signals go digitally through the 'Input Router' into the 'Channel 1-48 Input Module', which handles all signals also identical..

But ofcourse, if every fourth input (4, 8, 12, 16, 20, 24) gets static noise it does look like a hardware issue. Could be power supply to the input modules, but I can't see how that is set up from the block diagram. One thing I would try first, is to send the analog input 4 to mixer channels 1, 2, 3 and 4, and see if they all show the noise. If they do, it would seem the analog Mic/Line Inputs 4, 8, 12 etc have a common problem - and not the digital path going further into the mixer.

 

[SoulStick]

Hey Arjan, fellow Dutchy

I’m looking into the schematic diagram and the 3 input ad pcb’s are linked together to Go to the adda pcb. Here they are processed in groups of four(see picture)

Therefore I’m thinking it’s in the adda pcb board.

I rerouted the channels to other mixerchannels and there was no noise. But also no sound.
I also deteached the cable on the pcb board and it was still giving noise.

 

[Arjan P]

Ah, but that is indeed a wiring or logic schematic. The block diagram (from the user manual) does not show this level of detail.

Seems to me you are thinking in the right direction. Opening up the board hopefully will give more info, maybe a flat cable not seated right. Good luck!

 

[mixerizer]

This is fascinating, I am also sending good vibes for a perfect outcome!

May I ask if that schematic is available online? I scoured the Web and didn’t see that one! Would love to read a copy. Thanks if so!

 

[Arjan P]

@MickiKaufman Under the 'Documentation and Manuals' you can find lotsa stuff. The schematics are also linked in this topic (scroll down to post #16):
https://www.tascamforums.com/threads/service-manuals.55/
(I'm doing it like this so the original poster gets credit for supplying the link)

 

[SoulStick]

I also found them on this forum in the same thread Arjan P posted above
There are multiple schematic diagrams in the .zip file.
I used the revb version with the newest date.

 

[SoulStick]

A little update on the issue:

today I installed the firewire with my macbook. No analog inputs whatsoever and also in the digital channels the same noise on the same channels. I guess it has to be the master adda. So tomorrow I will take a very, very close look on that pcb.

 

[mixerizer]

Thanks guys! Snagged em. Hoping for an excellent outcome, SoulStick.