HD192 Blowing Fuses Ocassionally

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Phyl

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My MOTU HD192 has started blowing fuses about every two weeks, but only on power up. So far MOTU has suggested I toggle the 120V/220V selector switch back and forth to see it if helps. It doesn't. The unit is about 3 years old.

Anyone heard of others experiencing this sort of problem?
 
Phyl said:
My MOTU HD192 has started blowing fuses about every two weeks, but only on power up. So far MOTU has suggested I toggle the 120V/220V selector switch back and forth to see it if helps. It doesn't. The unit is about 3 years old.
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Some power rail is partially shorted. Probably a worn wire or a dendrite in a defective capacitor or a dendrite between two contacts on the board. I'd disassemble it, inspect all the wires, inspect the board for solder contamination (dendrites partially shorting between contacts, particularly at the power connector), and if you still don't find any problems, replace all the capacitors in the power supply, starting with any that look like they were made in China....

You might also try unplugging the FireWire cable before switching it on and see if the fuse blows when you plug the cable in instead of when you power it on. You might have a significant current leak between the DC output line and the ground in your FireWire cable.

If none of that helps, replace the fuse with a breaker. That way at least you don't have to keep replacing fuses. :D
 
dgatwood said:
Some power rail is partially shorted. Probably a worn wire or a dendrite in a defective capacitor or a dendrite between two contacts on the board. I'd disassemble it, inspect all the wires, inspect the board for solder contamination (dendrites partially shorting between contacts, particularly at the power connector), and if you still don't find any problems, replace all the capacitors in the power supply, starting with any that look like they were made in China....

You might also try unplugging the FireWire cable before switching it on and see if the fuse blows when you plug the cable in instead of when you power it on. You might have a significant current leak between the DC output line and the ground in your FireWire cable.

If none of that helps, replace the fuse with a breaker. That way at least you don't have to keep replacing fuses. :D
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the "every" Two Weeks... comment the OP mentioned is interesting.




there's always Ebay to sell used faulty gear. (jsu kiddinz..):p
 
COOLCAT said:
the "every" Two Weeks... comment the OP mentioned is interesting.
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Yeah. That's why I suspect it is drawing just a little bit more than it should be at power-on caused by some voltage leak somewhere. If it were drawing a lot more, it would blow every time you turned it on. but if it is just drawing a little more, then every time it does, it weakens the fuse just a little, and over a couple of weeks, it blows.

If you're not using slow-blow fuses, try that. They're designed for just this sort of situation, so that might cure the problem entirely, in which case I wouldn't worry too much about it.

Worst comes to worst, IIRC, MOTU has a flat $80 fee for out-of-warranty repairs. That's really pretty good---some companies would charge $80 just for the diagnostic fee.... :D
 
Thanks.

I'm using slow blow fuses. I like the idea of just putting a breaker in there. I've got a email in to MOTU; I suspect they'll have me send it in.
 
dgatwood said:
Some power rail is partially shorted. Probably a worn wire or a dendrite in a defective capacitor or a dendrite between two contacts on the board. :D
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i dont think i've ever experienced a partial short... doubt they exist... any chance you're leaving say the phantom power on sometimes and not others??? perhaps the extra in-rush current is a bit too much for the fuse... try turning the phantom off everytime you powere down and back on after turning on the system each time... gotta feeling it will go away... also ya might tey a fuse that's 1/4-1/2a more than speced... no more than that...
 
wow server is slow today... said it didnt post the first time... sorry double post..
 
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The unit isn't connected to any inputs/outputs that have phantom power applied.

Inputs are connected to mixer line outs, outputs are connected to mixer line ins. In any event, the mixer is powered up after the MOTU.
 
my bad... there's so many convertors with pre's out there now i just went with it... ya still might try the "SLIGHTLY" higher rated fuse... maybe it's marginaly inappropriate since it doesn't blow all the time....
 
.. ya still might try the "SLIGHTLY" higher rated fuse... maybe it's marginaly inappropriate since it doesn't blow all the time....
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i was going to suggest that but they are slow blow fuses and that points to a decent leak going on.
Power supply smoothing caps is where I'd look first.
 
Rodger Hartlett said:
i was going to suggest that but they are slow blow fuses and that points to a decent leak going on.
Power supply smoothing caps is where I'd look first.
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the fact that it only does it sporadicly and only on power-up says inrush current to me... supply filters will either cause hum or if dead shorted blow all the time... still it's worth checking i guess... kinda curious to find out now... a bit of a puzzle...
 
MOTU wants me to send it in - the good news is $80 for all out of warranty repairs, the bad news, I can't record any Megadeth wannabe wankers for a while.

Now that I think about it, that's good news too. ;-)
 
dementedchord said:
i dont think i've ever experienced a partial short... doubt they exist...
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By partial short, I mean a low but not zero resistance path to ground. For example, with lead-free solder, you can grow dendrites from one contact to another. If thin enough, they create what is technically a short, but is not thick enough to draw much current between the two contacts. The same thing can happen inside capacitors, IIRC.

When you get dendrites across power leads, this would cause significantly higher than normal current drain, but not enough to cause the circuit to fail... just enough to pop the fuse. If that's the cause, the problem will get progressively worse until you have enough of a short that it blows fuses constantly.
 
How Do you Replace the fuse on the HD192

I purchased an HD192 from Music Go Round .. and it was packed terrible when it was shipped .. and when it arrived it will not power up at all .. I want to check to see if the fuse got dislodged but I don't know exactly how you get to the fuse. There are "star" screws .. screws on the case .. screws on each of the XLR .. rather than go into this elaborate tear down .. and before I send it back .. I would love to know the procedure .. ?
 
Phyl said:
My MOTU HD192 has started blowing fuses about every two weeks, but only on power up. So far MOTU has suggested I toggle the 120V/220V selector switch back and forth to see it if helps. It doesn't. The unit is about 3 years old.

Anyone heard of others experiencing this sort of problem?
Click to expand...

I find that after I record old country style music my board will blow up the next time I try to run it without fail.

I'm certain that's your problem. change your genre. no more old country.

;-)
 
rich4a1 said:
I purchased an HD192 from Music Go Round .. and it was packed terrible when it was shipped .. and when it arrived it will not power up at all .. I want to check to see if the fuse got dislodged but I don't know exactly how you get to the fuse. There are "star" screws .. screws on the case .. screws on each of the XLR .. rather than go into this elaborate tear down .. and before I send it back .. I would love to know the procedure .. ?
Click to expand...

I would not try. If it worked before they shipped it, then I would contact the seller and arrange for them to file a claim with the shipper and get yourself a new one as a result of the claim. If it didn't work before they shipped it, then it is probably more than just a fuse. Either way, tearing into the thing is probably a bad idea and is probably a good way to end up stuck with a dead piece of hardware and a steep repair bill from MOTU.
 
rich4a1 said:
I purchased an HD192 from Music Go Round .. and it was packed terrible when it was shipped .. and when it arrived it will not power up at all .. I want to check to see if the fuse got dislodged but I don't know exactly how you get to the fuse. There are "star" screws .. screws on the case .. screws on each of the XLR .. rather than go into this elaborate tear down .. and before I send it back .. I would love to know the procedure .. ?
Click to expand...

In addition to the screws on the front and sides, you must also remove the screws around the XLR connectors on the back. A royal pain, but once inside, the fuze is easy to replace.
 
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