Gig adventure - emergency GLD surgery

TJ Cornish

Graduate
Jan 13, 2011
1,263
1
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St. Paul, MN
I just got back from a multi-day event. During rehearsal on day 3, the GLD-80 surface went dead. We replaced the IEC cable and it worked for a while, but a couple hours later went dead again. A fist bang brought it back to life once more.

After surviving the next session, we opened up the surface to figure out what was going on in the power supply. It turned out that the power supply input fuse was the issue. There isn't a fuse holder in the power supply - the fuse is an axial-leaded thing that stands vertically, and one of the leads had apparently broken (the fuse itself was intact). I soldered a jumper wire across the fuse, and we were up and running.

It was interesting to see the internal construction of the GLD. I was a little surprised that it's a standard ATX power supply (with some custom lead lengths) with only +/- 5V and +/- 12V. Most mixers have higher voltage rails from the power supply - the GLD must do up conversion somewhere for the analog section. Also interesting (but not particularly surprising) is that the system is based on a small PC system board with various subsystems connected via USB cables.

GLD fix.jpg

I'm a little conflicted about leaving the fuse bypassed. It seems unlikely to me that a circumstance will arise during the life of the board where the fuse would blow short of a power supply failure; the solution being replacing the power supply. It seems then, that I can either spend a bunch of time dismantling the board and power supply again, finding the correct axial fuse, repairing, and re-assembling, or I can simply use it as is, and in the unlikely event that it dies in the future, just replace the power supply at that time.

Am I missing something? Is it likely that if the power supply would fail, it would do so in such a manner that the lack of an input fuse would cause the power supply to take out the rest of the mixer?

P.S. Allen & Heath - this is now the second power supply in my various GLD gear that has failed on me in less than 3 years (power supply in AR2412 died last year). I would really appreciate it if you would spend the extra $.08 or whatever it takes to put non-crap power supplies in your stuff. I love the functionality, but you guys could learn a few things from Yamaha in the reliability department.
 
Re: Gig adventure - emergency GLD surgery

A&H have had some... issues with power supplies over the years.

If it really is just an ATX power supply, why not replace it with one that actually works well over time?
 
Re: Gig adventure - emergency GLD surgery

I'd be worried that a failure could cause a fire with that fuse "bypassed" ...

While I'm sure that's theoretically possible, it does not seem to me that it would be likely. Most power supply failures I've experienced are single component failures that are non-spectacular - they just go dead. The only really exciting failure I can recall was a voltage regulator module on a server maybe 10 or 12 years ago where we got some smoke before the part opened up. I'm certainly curious if others have had different experiences.
 
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Re: Gig adventure - emergency GLD surgery

A&H have had some... issues with power supplies over the years.

If it really is just an ATX power supply, why not replace it with one that actually works well over time?

I'm not sure what issues you are recalling or from what era, but back in the olden days, power supply failures in mixers were a significant enough issue industry-wide that a spare in the rack was pretty much expected.

In the case of the GLD surface, it's a standard ATX power supply in the sense that all of the voltages and connectors are what you'd expect from an ATX power supply, however the wiring is likely customized - the lengths are specific going to the various subsystems. It also has a hard power switch on the back of the power supply chassis. I'm sure it would be possible to Frankenstein the wiring from my existing power supply onto something else of possibly higher quality, but I'm hoping that I have now met my quota of power supply failures and that I won't have more trouble.
 
Re: Gig adventure - emergency GLD surgery

It was interesting to see the internal construction of the GLD.

Thanks for sharing. Hopefully my life is never that interesting--the church where I mix has likewise had an AR2412 power supply go flaky (it would eventually power up the unit, but only about 20 minutes after switching it on...) that was replaced under warranty.

That fuse is there for a reason so count me as another vote in favour of replacement rather than bypassing it.