Dreaded no sound out of Mains 24FX

[drumbumdave]

Hey guys first time poster. I have been following the Peavey forums since i acquired my 24FX first Gen. I have had it all but
2 weeks and i now have the dreaded no main out signal. Also do not have RCA out or SUB out that works as a temp. solution.
I decided to open up the mixer and have a look. It does have the update that Jim H talks about. New capacitor/resistor.
As far as not having any signal coming out of these jacks, everything else seems to work. Digital read out screen operates as should.
When i first got board it worked fine. But did have extra noise in the signal path to my powered speakers. Way to much actually. I was using
a dual 31 band EQ connected to R and L main outs. So last night i disconnected the EQ and messed around with the parametric and
graphic EQ's. Along with the feedback ferret and effects. Also tried the dual mono and subwoofer setting for output. I also have powered subs. And out of no where the signal was gone . I could play MP3 using RCA in's. I could hear mics using my headphones. I guess what i want
is some ideas of where to go from here? Jim h states in a picture on a different post about where the resister and capacitor go. He
says resistor 100k ohm between R133 and R142. On my mixer it is between R133 and C46. Any ideas? Mixer is dirty on inside too. Can i
blow out and or spray with electronic cleaner?
Thanks for any help. How do i post pics?

Dave

[Dano0369]

Hell-o ; I would suggest a trip to a peavey authorized service center. The original fx didnt have enough processing power to operate all you could open up. Always keep an eye on your cpu % Good luck.

[drumbumdave]

Thanks Dano. I did read about watching the CPU %. I never went over 65% while actually using the board (band practice) . But messing with it to check everything out I may have over done it.

[Dano0369]

Hey Dave; I have my 16fx close to me , in the shop today. i turned one everything you listed cpu bouncing between 82-83. i hit utility usb stick and immediately got a need more cpu message . hope you haven't popped that . good luck

[drumbumdave]

Well i may have a different issue than i thought. Feel stupid. What happened is we were not using the first 8 channels at band practice.
So last Saturday when this all happened i started by moving everything down starting with channel 1. I only plugged four mics in. 2 singers and
two mics for guitar amps. (to hear in my IEM). So when i got home from work today i started scratching my head and went through mixer again.
I decided to check all channels before calling peavey repair dept. When i got to channel 5, it worked. And so did the rest. So channel 1-4 are NOT
working. They show signal with PFL on and can hear in headphones. Otherwise the MAIN out, SUB outs and REC out does not work. So new issue.
Does anybody know why channels 1-4 are dead? Again thanks Dano.
Dave

[Wooferhound]

How do you have them assigned on the Patching Switches ?

[drumbumdave]

I very carefully have checked every single channel to make sure they are identical as far as the routing and everything else. I sent an email off to Peavey repair department to see if they come back with any ideas. I am now wondering if all four channels are maybe combined as a group connected to a ribbon cable or something. Seems weird that the four are together.
Dave

[jim h]

I don't see any reason for 1-4 specifically, to be dead. 1&2, 3&4 share power supplies, but are independently protected from failures.

If something shorted on channel 2, for example, the series power supply protection would trip and kill channel 1 (along with 2). But 3 and 4 should continue to work.


The channel boards are broken into 8 channel segments. That seemingly would eliminate the interconnection between channel circuit boards. If that was the failure point, all 8 would be dead.


I see 1&2 share a cable to the pre-amp, but 3&4 have their own cable. So that is unlikely to be the problem.


Bottom line, I don't see anything common to 1-4 that could cause that type of failure.


If you have PFL, then most of the channel is working. Can you tell if the signal is getting to the FX module? Turn Aux 5 send knob (in the channel up), turn up Aux 5 master, press AFL next to Aux 5 master you should see the signal on the meters. Remember, the channel fader must be up for the Aux 5 send to work. This is going to tell us if the channel fader is working or not. I'm also going to assume Aux 1-4 works, since they are essentially the same signal as the PFL.

[drumbumdave]

Thank you Jim for your help. I did what you suggested and the channel faders on 1-4 must me bad. There was no signal. I confirmed by testing
channel 5 the same way and got signal. In your opinion where do i stand? I do solder now and then and fix cables. But it looks intimidating to say
the least. Is this something i can fix possibly? Is this older mixer worth the money to send in and get fixed? I do not need all the channels but
will admit i like my gear in working order. Thanks for your help again.
Dave

[jim h]

Normally, faders don't just die completely, unless they've been physically damaged.

With signal going into the channel, can you wiggle or move the faders around and see if signal passes?

It would sure be bad to go through all of the effort of changing them out only to find that wasn't the problem.

[drumbumdave]

I tried wiggling them with no success. Could it be a simple ribbon cable is bad? Seems very odd like something's not hooked up inside
Dave

[drumbumdave]

Jim H. or anyone for that matter. Please help. I now have channel 12 fader go bad . Can someone confirm what exact fader part # i need to replace these?
24FX mixer not FX2.. Full compass has two faders that say fit the 24FX part#31191064 and 31191065. I don't know the difference?
Thanks

[jim h]

Depending on the age of your mixer, it's possible neither will work. At some point, we had to change the faders and the new ones (like the ones you are looking at) don't fit the old circuit boards.We need to identify the pcb number to know for sure which fader you need.

If you're doing the work, you should remove the bottom of the mixer and look at the circuit board with the bad channel. See if you can find an 8 digit number, it might have a letter too. For example, 32101084C might be one. Keep in mind, the number is etched in copper...so it might be a little hard to see.

[drumbumdave]

Ok i will check but it will be a couple weeks when i get to it. Thanks

[drumbumdave]

Ok i have mixer taken apart. Serial # K0278209 00512480/AGC
I believe i have found the faders i need. (Top Pic) Peavey # 31190159. Also when i was measuring resistance i noticed the right and left main faders where quite different from one another. Is this normal? They work fine
Thanks