mackie ppm608s problem

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mackie ppm608s problem

Postby ampcabinets on Tue Jan 31, 2017 10:28 pm

here's the deal:
channels 1, 5,6,7, and 8 all work fine

channels 2,3, and 4 have a slight hum and only the inserts work.
I get nothing from the mix and line inputs.
The effects all work.

can't find a schematic, either, mackie only posts them for the 408 and 808 series, and thoughtfully left out the 608 series.

I found some block diagrams and 'some' shematics, but none for the input board.
The amp and power supply boards are as-new.

If anyone knows about these things, I could stand a bit of help.

I suspect it is one of the caps or one of the mixer chips (on board the input section) has gone south.

But, what do I know...........nothing.
I am stumped because the insets all work, but 2, 3, and 4 only work on the inserts.


Thanks in advance if anyone has a heads up.



I am trying to learn, but things take time.........
no phone, no pool no pets....I ain't got no cigarettes!...............Roger MIller
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Re: mackie ppm608s problem

Postby ampcabinets on Tue Feb 07, 2017 6:45 pm

well, so far I have narrowed it to the preamps, jrc4565 chips. got them ordered, that smt stuff, also, needs a hefty magnifying glass.

all I can do is give it a shot.

caps seem to be good, signal is good to that point.
I may need to replace some op amps, too, but I am still reading the spec sheet on the chips.
I am too old to learn new stuff, but what the heck, give it the old grade school try.

But I still don't understand the 'insert' vs mic input thing.

Unless the insert does not pass through the preamp, which may be the case.
still haven't found a schematic.
no phone, no pool no pets....I ain't got no cigarettes!...............Roger MIller
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Re: mackie ppm608s problem

Postby ampcabinets on Mon Feb 20, 2017 10:59 pm

after repairing channels 2 and 3, when I was going to start on channel 4, I got a call from a fellow tech in Austin, who had a new face panel for 50 bucks.
smd's or smt's, are, actually not that hard to deal with.

There are about 7-10 op amps per channel.

problem solved

However, replacing the 4565 drivers (op amps) and TI op amps, on both the input sections and rifling through several others, (on channels 2 and 3, which took me a LOT of time to: 1) find what I was looking for by comparison to other channels on the scope) and then r&r'ing the part(s)...get good signal, go to the next) it was cost effective to have to not going through the others, for 50 bucks.

cmos is cmos and when things decide to go, you have to hope they didn't use 15 different amps, preamps and op-amps, not to mention mixers(chips), because the factor that affected the first stage, most likey didn't stop there.

mackie ppm608 is plenty stout for bar gigs. That is if you only need a 2 channel mix, one main, one monitor, one stereo mains.

has plenty of poot for your vocals.
no phone, no pool no pets....I ain't got no cigarettes!...............Roger MIller
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