mackie 1604 vlz-pro malefunction

I'm operating "naked" right now - so thank's for that information, maybe this solves the problem right away, i'll give that a try on the weekend.

cheers
christoph

News on my problem - I re-attached the all the ribbon cables to the in/output pod (which btw is fully assembled) and the error is the same like when it first appeared. rude solo light is flashing, all channel solo leds are on, and the meter leds are all on as well.

here's the funny part: as soon as i plug a cable in the main out (to a headphone amp as a load) the mixer "looks" normal for a few seconds but then the meter leds come back, noise gets audible and hot solder can be smelled. I tried that 3 times for a few seconds but couldn't really spot where the smell came from. the caps all look good, but i found the ribbon cable that causes all the channel solo leds to go on. I think i'll disassemble the in/output pod as well and have a look at the pcb there.

many thanks for the help so far
christoph

i'm still wasn't able to find the fault, it seems like it's definitely the In/Output pod that causes the shorting. Everytime I connect it to the main pcb, all the leds go on. But there is no obvious sign of faulty components, I can't really track anything down.

any last ideas/hints?
christoph

Time is marching on - if you really want to use this mixer you might like to contact a Mackie repair centre.

If you want to learn about advanced faulting - you now have an opportunity, although sometimes even very experienced people (me!) - find locating this type of problem difficult!

I have already mentioning 'sniffing' for hot components (and there will be one if considerable current is being drawn from the supply). If you have an ohmmeter capable of measuring VERY low resistances you can probe around the PCB power supply rails until you find the lowest resistance (the short circuit). The other method, which is somewhat destructive, is to cut the power tracks at various points and find the short. Sometimes this is easy if there are wire links - which can easily be removed.
If you try this method - cut half way - locate which half the fault is in, then cut half way again. Eventually you will home in on the fault.

John G

It's been a while, but I'm finally able to post some good news on that one. With the help of an more experienced electrician, I was able to trace down the fault to the "aux returns" area on the mainboard, and luckily I spotted a burnt smd cap, which we replaced. Now everything seems fine. The cap was sitting on the power supply line of a chip and due to its short, it connected the negative power supply to ground.

Many thanks to everyone who helped - especially john.
Christoph

Well done - glad to hear that you have located the fault. This is the way to learn - next time you have to work on this (or another item) - it will become progressively easier - as you gain confidence and experience!

Isn't the Web wonderful?!!

John

Good job!
Now you will have something to compare with your DIY preamps, which will blow poor mackie right into puget sound for the deep six.

Now you will have something to compare with your DIY preamps, which will blow poor mackie right into puget sound for the deep six.

Click to expand...

Hehe - It's just a backup whenever I run out of "dedicated" preamps, or sometimes I use it for monitoring during recording and as a submixer on stage. I found the micpres quite useful for "non-crucial" signals.

regards
christoph

Sorry to bring back a "moldy oldie" I've got a the same situation... I got excited when I tracked down the -16v supply was down (up?) to -3 at the LM337, replaced that and got my -16v back when the PSU was isolated, but -alas still square wave output and Christmas tree lights with the board attached, so based on previous posts, sounds like I should be checking those coupling caps on the neg power rail for ICs on the main board... -does this sound reasonable?

Thanks in advance

Oh- I've been mostly lurking on and off for ages and I'm humbled by the expertise on this board and glad there's such a great resource out there in the great big "inter-web"

Mark