Replacing ALL of the caps on my 1248 and one on my 16A…

[nk_e]

Hi all,

I’m wondering if I did something wrong or am just suffering from extraordinarily bad luck.

I have a 1248 and 16A both about 4 years old.

The 1248 suddenly started to show all analog input levels pegged to the top constantly. No audio was available, nor did it output a sound…just pegged meters. The meters pegged even when there was nothing physically plugged into the unit besides a power cable.

I eventually pulled it and replaced it in my setup with an old 828mk3 hybrid.

About a month later, my 16A started to have trouble getting through its start up sequence. After 2 - 4 of the “undulating bar patterns” at start up, it would simply stop and freeze. Turning the unit on an off would eventually get it to boot and it operated normally.

However, this rare event turned much more regular and, eventually, successfully completing the start up sequence became the rare exception. I pulled this unit too.

I called MOTU tech support for help diagnosing or perhaps shipping the units to them for repair. The tech guy didn’t know what was happening and told me that since the units were out of warranty, they wouldn’t take them.

I have a local repair shop here that does good work. They opened the units and told me that ALL of the caps on the 1248 need to be replaced and that one of the caps on the 16A needs to be replaced.

So my question is: What cause capacitors to go belly up? So many in one unit is odd. Did I do something wrong?

• Power surge? I don’t think a power surge happened as nothing else was effected, and the units are plugged into an expensive APC power tower with battery backup.
  
  They are mounted in an argosy rack unit next to each other and I rarely turn them off. Did they just get too hot?
  
  Was it just a bad batch of capacitors that happened to get stuffed into the 1248 and just plain bad luck on the 16a?

I mostly want to know because I don’t want have this problem again, and if I did something wrong I want to avoid doing it. Pulling apart my setup was a strategic PIA that I’d rather avoid.

Anyway, if you’ve made it this far, thank you. Any thoughts appreciated.

[HCMarkus]

Bad luck... So sorry this has happened for you!

Probably bad caps, but heat never helps. Might want to leave 1/2 space above each in the the rack if possible. Glad you have a repair guy who can handle the job.

[mikehalloran]

We see reports of bad power supply caps on old units that have been in continuous use for a decade or more. This, however, is most unusual.

I would be checking the Voltage coming out of that APC. It shouldn’t exceed 120V.

[slliwbor]

motu power supply copy.jpg (232.6 KiB) Viewed 1970 times

Hi all, ,

looking for some assistance. My 1248 has blown capacitors , (2nd time) but this time Motu is able to provide me a replacement power supply for $30 . better than the $220 shop fix, I opened my 1248 , it looks pretty straight forward except for this piece in the photo .. I cant tell it pulls apart or not , its not budging with a pry tool. It has 1 set of pins that looks like it connects the Power supply board , like a ribbon should.

[jjgr]

Yes, it pulls off. I did it on my 1248 recently.

It doesn't come off easily though. Pull each corner up a bit at a time and alternate corners to keep the board flat and avoid bending the pins.

[monkey man]

I'd leave 1 rack space above every unit 'cause the mega-multi-channel AVB units apparently generate a lot of heat.

I'd blame heat first before anything else but Mike could be onto something.

[jjgr]

I had the pegged meters and no audio symptom on my 1248. Since I am a seasoned electronics technician, I usually do my own repairs. I removed the capacitors from the power supply and tested each one of them. They were all within or above spec so no blown capacitors there. I put them back in.

Knowing that the firmware was not up to date, I did an update to the latest firmware and then loaded my configuration I had saved before. Now everything is working normally. I suspect that the configuration it was working with got glitched somehow and reloading it fixed the problem.

I don't believe that my problem was caused by heat because it showed up on a cold start with a room temperature around 72 deg F.

[slliwbor]

Thank you jjgr for the confirmation and insight regarding removal. Power supply arrives tomorrow!

[monkey man]

I don't believe that my problem was caused by heat because it showed up on a cold start with a room temperature around 72 deg F.

Yeah, I think the implication, at least it was in my case, was that heat might've caused accelerated cap degradation, but you're fine there anyway.

Well-done man.

[Phil O]

Sounds suspicious to me. Anything that would cause ALL the capacitors in a unit to fail at once would cause a lot more damage than just capacitor failure. How did they determine that they are all bad? I'm calling BS. Just sayin.

[EMRR]

Yes, heat causes accelerated degradation, caps are rated for a life span that derates with heat. That can really dry out all the caps in a unit experiencing the same heat conditions. These units run hot, they must have open space above and below (THE MANUALS SAY SO!), and they still get warm like that. Room temp has nothing to do with it. They really need vents for air flow. Old broadcast tube gear generally runs cooler than these things, unless there's power tubes involved. Maybe I'll get out the drill.......

[Phil O]

That can really dry out all the caps in a unit experiencing the same heat conditions.

You're just talking about the electrolitics, right?

[EMRR]

That can really dry out all the caps in a unit experiencing the same heat conditions.

You're just talking about the electrolitics, right?

Right. Usually also the majority in anything modern.

[nk_e]

FWIW, I now leave a 1/2 rack space open on each side of my two 16As and 828ES units. I end up losing 2U of rack space, and it looked a little funky at first… BUT I’ve had no heat related issues since even if I leave the units on for extended periods. They run warm (as they typically do), but not extremely hot as they used to.

I can’t recommend spacing them enough.

(And in retrospect I feel like a bit of an idiot for not realizing this sooner. The complete loss of my 1248 may have been related to this. It was an expensive lesson.)

[James Steele]

Ugh. Which sucks for me as I’m precious short of rack space.