Anyone with Allen & Heath repair skills?

J

Jeff Hague

Freshman
Jan 12, 2011
86
0
6
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Mechanicsville, Virginia, United States
www.richmondproaudio.com
My GL2400 has developed a nasty hiss in the left main output. (I have isolated it and it is definately in the left main of the board.)
Im wondering if it could be as simple as a loose ribbon cable or an IC that isnt seated well in a socket. Is it worth opening it up and having a look around before sending it off for repair? Its not under warranty so Im not afraid to open it but if its likely a "real" repair, Id just as soon save myself the trouble...
Thanks!
 
Re: Anyone with Allen & Heath repair skills?

All ICs are simply soldered to the board itself. You can go ahead and check the ribbon cable, but this sounds more like a component level issue to me.
 
Re: Anyone with Allen & Heath repair skills?

For what it's worth, if your component level skills aren't up to snuff & a ribbon cable reseat doesn't fix the problem, you can always order a new master channel card for A&H via American Musical Supply's service dept. and drop it in there. Shouldn't be very expensive.

Greg
 
Re: Anyone with Allen & Heath repair skills?

One more thing I might suggest is to remove each channel from the large ribbon cable, one at a time, just to verify that the hiss noise is not being introduced into the left channel from any of the other boards. That way if you should decide to invest in a new circuit board, you will be getting the correct one.
 
Re: Anyone with Allen & Heath repair skills?

Does the hiss dissapear when the left mute is engaged --------yes---------Replace U4
no
Does the hiss dissapear when the left fader is at minimum-----yes---------Replace U3
no
Does the hiss dissapear when there are no LR(mix) channel buttons down----no-----Replace U1,U2,Q2 or Q4
yes
Engage LR(mix) buttons one at a time and find which channel is generating hiss
apply above methodology to faulty channel
 
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Followup: Anyone with Allen & Heath repair skills?

I finally got the opprotunity to open the GL up and poke around. My component level "skills" are at least 20 years out of date so all I intended to do was reseat ribbon cables and if that fixed it; great, if not; take it to the shop...
Quite a few of them had some travel to be fully seated (some nearly an 1/8 of an inch!) so I felt it was a good exercise even if it didnt solve the hiss. It was also pretty dusty inside so I cleaned it out real good while there.
I didnt have time or room to bring anything but the board into my office so all I could do for bench testing was headphones but it did seem to solve the problem. I could make it hiss (both L & R outputs the same) by turning up the headphone output but only at extreme levels - much higher than I have ever had to run the board. I also noticed that assigning groups and channels to the LR buss added incremental levels of hiss but again, only at extreme levels and that behaviour is expected anyway.
Yesterday I got to check it out with the full rig in a live situation and I am happy to report that simply reseating the ribbon cables and clecning the dust out solved the problem - no more hiss! It was an outdoor festival too so I got to run the system pretty hot and the hiss is definately gone.
Thanks all for the posts!

Jeff
 
Re: New issue...: Anyone with Allen & Heath repair skills?

So the cable reset fix didnt last long. Saturday the hiss was back and a new problem has surfaced, although it may have been there all along but I didnt notice it.
I run the GL for house and a MixWiz for monitors and sometimes I run aux 6 from the GL into a channel on the Mixwiz so I can get my FOH talkback and canned music into the monitor mixes.
To minimize the hiss I have found that I can run my L&R faders much lower than usual - minus 15 or so insted of minus 5 to 0 - and run all other faders hotter than usual so that "solved" that issue. But, during soundcheck the band stopped dead and asked that I take the bass guitar out of all the monitor mixes - it was only up in 1 mix on the mixwiz. Scratched head, muted stuff, messed around and it went away. The band did 1 more song for sound check and were happy except that they said for a moment they heard the lead guitar in all monitor mixes but then it went away too - weird... After sound check I had some time to fiddle with things and realized that whenever I hit a PFL button or turned up the headphone output, it showed up in all monitor mixes. The monitor bus is being fed through aux 6 at a pretty high level. I mixed the show without using my cans which sucked but I got through it.
So now I guess Im back to replacing PC boards. Im confused a bit though because the hiss is in the left channel but the monitor circuitry is on the right PC board - maybe I need to replace both?
 
Re: New issue...: Anyone with Allen & Heath repair skills?

Fire off an email to David Mitchell at American Music Supply and explain the issues. He's pretty sharp and will probably have the right answer for you. He's been very helpful for me in regards to A&H boards.

Greg
 
Followup - Re: New issue...: Anyone with Allen & Heath repair skills?

Greg Cameron said:
Fire off an email to David Mitchell at American Music Supply and explain the issues. He's pretty sharp and will probably have the right answer for you. He's been very helpful for me in regards to A&H boards.

Greg
Click to expand...

I did chat with David and he was quite helpful.
I wound up reseating the cable again and then applying a bead of hot glue to the connectors - I noticed all the other ribbon cables were done that way except the main one... I have now used it on 5 or 6 shows and so far, so good - no hiss and no bleed from the PFL bus to the auxes.

Thanks!
 
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