Mackie 1604 charming problems

[nylicens]

A question that I have is: did you use both rail voltages. (ie: + & - 15Vdc)?
...

Yes. -16 runs fine. +16 is the problem.

[Jazz P Bass]

This schematic is confusing as all get out.
I guess it makes more sense with the unit in front of you.

On page 3, upper right is shown the head phone ic power supply.
It's labeled +16V-PHN & -16V-PHN.
The connector is labeled J36-2 & J36-3.
Where does this go to? (the J36 header)
Can it be disconnected?

[nylicens]

This schematic is confusing as all get out.
I guess it makes more sense with the unit in front of you.

Only a bit. I have 3 different schematics for the 1604. The last one I got reflected what I actually have.

On page 3, upper right is shown the head phone ic power supply.
It's labeled +16V-PHN & -16V-PHN.
The connector is labeled J36-2 & J36-3.
Where does this go to? (the J36 header)
Can it be disconnected?

This is on the main board and I tried disconnecting that first, being the suspicious person that I am.

I just went thru the pod board and checked every ground to the +16 supply. 155K with black lead on the +16 supply and 47K when I checked with the leads reversed. I am beginning to think the pod board is OK and something that it is responsible for supplying to the main board trips out the +16 supply. Back to more intense studying of the schematic.

[g1]

I am beginning to think the pod board is OK and something that it is responsible for supplying to the main board trips out the +16 supply. Back to more intense studying of the schematic.

Good idea. Originally when you said the +16 held up with the pod disconnected, I assumed the pod had to be responsible. But it could be there is excess current elsewhere and the pod is just putting it over the edge.
Current measurements in series with the +16 line out of the regulator would be helpful.
The other thing I was wondering about was the use of mica and silpad at the regulator. You want a very thin layer between the reg and heatsink, would be best to use one or the other type of insulator.

Edit: The part I don't get is why your gator clips were overheating if the pod is all good.

[nylicens]

Good idea. Originally when you said the +16 held up with the pod disconnected, I assumed the pod had to be responsible.

As did I.

...The part I don't get is why your gator clips were overheating if the pod is all good.

As I look at the schematic, I now wonder if the pod board supplies individual grounds to the main board. Take a look at the Ch1 example and the pod board pinouts.





Can it be that the grounds for each channel are unique and are supplied from the pod board??

[nylicens]

Can it be that the grounds for each channel are unique and are supplied from the pod board??

Finally got a chance to get back to this problem. Discovered that +16 line on main board measured 125Ω to ground. Connecting the POD board P3 cable dropped it to 1-2Ω. Hmmmm.

[nylicens]

Can it be that the grounds for each channel are unique and are supplied from the pod board??

Certainly seems so. I dove in and removed the main board from the front panel (ugh, too many knobs!) Close inspection revealed not much but even closer inspection of the 11-16 channels (the ones supplied by P3 from the POD) revealed the following bypass caps:

This is what 15 of the caps looked like:



And this is what Ch 11 looked like:



Looks like tomorrow will be smd soldering day

[The Dude]

That appears to be on the +15 line. You can probably just remove it without replacing and the thing will still work just fine. Or at least you can remove it and see if your short goes away.

[nylicens]

That appears to be on the +15 line. You can probably just remove it without replacing and the thing will still work just fine. Or at least you can remove it and see if your short goes away.

Replaced the cap with one I had laying around (with a bit of fiddling) and connected all back up and it "seems" to be working again. Now to put everything back together and see how many parts I have left over :-)

Thanks to all for your help and suggestions!

[Jazz P Bass]

It is a real treat removing all of the knobs & nuts.
Then people wonder why there is a $200.00 charge for changing out a ten cent capacitor."

[nylicens]

It is a real treat removing all of the knobs & nuts.
Then people wonder why there is a $200.00 charge for changing out a ten cent capacitor."

And there's nothing like getting it all reassembled and forgetting to put in the slider pot shield.

[g1]

I used to like saying "like having to pull the engine to change the spark plugs". But with the longer lifespan of modern plugs, and the shorter lifespan of modern electronics, now I say "like having to pull the engine to change the oil".

[nylicens]

And there's nothing like getting it all reassembled and forgetting to put in the slider pot shield.

What's worse is getting it all back together and then moving the insulation on the bench and finding to pod board shield. No wonder I was wondering why I had 2 allen screws leftover.

[guitardad]

It is a real treat removing all of the knobs & nuts.
Then people wonder why there is a $200.00 charge for changing out a ten cent capacitor."

I do work for a few local shops and they think all these mixers are modular and 10 minute repairs. So I took one of the owners to the shop and started a 24CH Yamaha board repair disassembly. I said now you see why mixers have such high labor? They are built for quick factory assembly, not for servicers. He said that's like transmission repair on a smaller scale. Damn that's alot of parts to keep track of!!

[Jazz P Bass]

Damn that's alot of parts to keep track of!!

Do not throw out those butter tubs.



Then there is the Mackie mixer boards where the whole thing is one board.
Hint: You are going to need a lot of 'butter tubs'.