Mackie 1604-VLZ3 OL/Mute LED issue?

[turborat]

Hi,

I have the above mackie mixer that I'm trying to repair. It initially wouldn't power up at all and I found the rectifier on the PSU had died, replacing that seems to have got the power supply back up and running ok.

The issue I have now is that as soon as you power the unit up (with only the main board & PSU connected together), every channels red "OL/Mute" LED's are constantly lit and the "Rude Solo" LED is flashing. I've confirmed that the +/- 16v & +48v supply rails are all ok (even with the main board connected) but I just can't work out what could be causing this now...

Has anyone got any ideas or had experience of repairing these mixers before?

TIA

 

[turk 182]

without more info i would think that this is the result of an open ground....could also be from dc on what should be a ground...

 

[turborat]

Thanks for getting back to me. I can post the service manual if that helps? All ground points seem to measure ok....

 

[turk 182]

have the schematic no worries.... are the main meters pegged or dead? if indeed all grounds are good then look at U1727 that IC is a quad and drives the main meters and rude solo function and is likely blown.

i hope you have some current limiting in place!

 

[turborat]

Thanks again.

Sorry for the simple question, but what do you mean when you say "are the main meters pegged or dead?"?

Also I can't seem to find the IC U1727 on the main board at all, the numbers don't seem to go that high?

 

[turk 182]

???? not familiar with silk screen designations or the lack thereof ....i would venture you still have not disassembled this enough to see what i'm talking about.

main meters...you know those ladders of led's that tell you what level the signals you've selected on your master section controls to tell you what's what look like this...

 

[turborat]

I actually have the unit completely stripped down with the main boards silk screening completely visible but like I mention, there isn't a U1727 I can see. I also understand what the main meters are but I don't understand what you mean by "pegged or dead2? I've attached a picture of the main board I have. You will see I have removed one of the LM339 IC's. It looked like it had some heat damage compared to the others so I remove this to see if that helped (which it didn't).

Thanks again for getting back to me.

 

[David Morison]

"Pegged" = all lights full on, even if there is no signal present.
"Dead" = no lights on even when you know there is signal present.

 

[turk 182]

thanks David!

 

[turborat]

Thanks David,

I've attached a short video showing the current state of the board (easier than trying to explain). It stays in this state no matter what I try.

Thanks

 

[TurnAround]

hey folks, having the same problem here with my Mackie 1604 vzl pro mixer. All "OL/Mute" lites are on solid, no mute button engaged, "Rude Solo" flashes constantly with no sound through anything and no solo buttons engaged. I can start a new thread if need be, but have you found a solution? Is it the infamous U1727??

 

[turk 182]

just because the buttons aren't physically pressed down does not mean there isn't a "short" across the switch, try a cleaning with a good quality contact cleaner.

 

[TurnAround]

I've got a can of deoxit and will prob spray it down but the problem feels more systemic

 

[TurnAround]

yes I have a can of deoxit and will try cleaning, but it seems like there is a more systemic problem. No lights or switches function other than the solid mute buttons and the incessantly flashing "Rude Solo" light. No sound through the board and the meters are dead. Solo buttons and mute buttons do nothing when pushed. You can see in the picture all "OL" mute lights are on and nothing changes regardless of buttons pushed. The funny thing is the buttons worked when I pulled it out of the box and then stopped working. Worried something blew

 

[turk 182]

with what your describing i'd expect the loss of a voltage rail or an open ground.