Any Yamaha electronic gurus out there?

[Jools4001]

Murphy's law has it that as soon as I've found a buyer with cash waiting for my Yamaha MG24/14FX than the right hand channel of the stereo bus seems to have gone kaput!

I've got a computer tech background (from the days when we used to use multimeters and oscilloscopes to fix mainframes), so I've opened it up to see if there is anything obvious like a loose ribbon cable or connector but can't see anything untoward.

All the input and master sections are made up of big surface mount boards, the input modules handle 8 channels each and the master section is just one big board that the inputs are ribbon cabled to and the FX piggy backs onto.

Being surface mount stuff I guess that taking it to a tech for any repair is going to be more expensive than the desk is worth and the Presonus desk that the sale was going to contribute to will have to wait.

I know it's a long shot but if there is anyone out there has any low down on yamaha internals and any 'known' faults I'd like to hear it.

 

[wcriley]

Did you clean and reseat the ribbon cables while you had it open?

If your mixer is like my little MG124cx, the ribbons don't have male connectors...just tinned wires shoved into the female connectors on the board.

I've not had any problems in the master section, but I loose individual channels periodically. Cleaning the ribbon connections bring them back.

 

[Jools4001]

Yeah, it's the same deal with the ribbon cables - just tinned wires straight into the connector. Good to have someone confirm that they could be a prime suspect.

I don't have any contact cleaner right now, so after I'd pulled a couple of ribbon cables out and re-seated them (just a couple from the master board to the boards carrying the output connectors) I decided to button it back up again until I have time to give every connector, pot and fader a good going over with Deoxit. The board is needed this week for the band duties that it's been performing reliably for years, rehearsal on Thursday and a Saturday gig, so I didn't want to introduce more problems before then.

I only found out that the right channel was out when I was demoing it...I run both mains in mono for my own band, from the mono output as well - so I haven't tried using the stereo outs for years. We've got a bit of a break after that until the next gig on 15th Nov, so I'll get some contact cleaner and give it a good go over on Sunday.

If it fixes it and it sells, that'll be great, if not I'll probably pull the trigger on the Presonus by then anyway.

Thanks for your help

 

[Eight_Stringer]

FWIW, Yamaha desks, had a few across the bench latterly, the flat ribbon link cables are very good usually. These desks have active balanced output stages, ie opamp in inverse driven parallel configuration. On one desk, it had reverse power applied, ie a power amp output was connected to the main out on the desk. With a magnifying glass you can see the distressed components and or cracked SIP IC. Fair amount of dismantling to get at these pcb assemblies, which means you run the risk of creating new problems while looking for the original fault(s). Maybe less problematic to find a competent audio tech, depends on what you earn an hour to what he charges per hour. HTH.

 

[Jools4001]

Sure does Eight Stringer. I can't imagine how it would've had a power amp output applied to it because everything on the power output side is speakon.

But...it's not impossible, I loaned the desk to my drummer who also plays with a folkie band that has a lot of musicians and instruments (they're also the people who want to buy it, so I let them borrow it for a try out at rehearsal). They've got a very experienced sound guy, but I know that they use a powered mixer at the moment so I guess they used the Yamaha into the poweramp section of that...not impossible that some wires got crossed.

Of course, I know and trust these guys, but I didn't check it out before I loaned it to them, so lesson learned if that is the case.