j.frad

Hey guys.
So we have a bunch of digi 192s here and one started making a little Pop noise when turning on. Last time I powered it up it made a louder noise and blew its power supply. Another studio in town had the same thing and theirs eventually blew the PSU.

The board is quite a big thing but the fault seems to be at the very input, just before a relay. I have a melted resistor and a blown Thermistor.

Now the problem is that I can't figure out the value for that thermistor, the only writing on it is 10SP 010. Can anyone help me figure that out? I've been searching for a while and couldn't find any replacement.

Thanks a lot guys!
jules


pucho812

I've yet to have one of those switching supplies blow up and stop working. However I have had many a/d and d/a cards go out which will cause the unit to not work until the faulty card is replaced or not connected. I think most of the 192 issues are heat related and the unit doesn't have proper ventilation but I can't think of a place to put a bigger fan.
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.

j.frad

Maybe only 192s in belgium blow up... Ours are properly ventilated so I'm not sure it would be the problem. I really have fried components on the board!
I would use a thermistor to control the fan speed maybe... not in the power supply. In which case does it make sense to use a thermistor at the input of a power supply?

V9977

I have seen thermistors on the mains side of a psu many times
to prevent inrush current at switch-on. From cold power-up the thermistor
has a higher resistance and after a short while it heats-up
lowering it's resistance and thus limmiting the current surge at start-up.
However, with a catasrtophic failure as you are describing I would suspect
something else has caused it to burn-up this way.

I would expect the component to be NTC (negative temperature coefficient)
and the lowest ohms you can get ahold of.

I can't help with a definate id I'm afraid.
CAUTION:  Equipment is alive

j.frad

Yes you are helping! Physically it looks like NTCs I've found. But common values are 10Ohm or 10Kohm and I have no idea what to try, if you suggest the lower value, I'll keep it in mind. I don't know if the range is so important in my case...

V9977

Yes the range would be quite important in this case. 10K would be way
too high if it is used in the manner I described above. 10R would be just
right, however you must first find what caused the component
to fail in this way. I cannot stress this enough.

It sounds like there might be a short somewhere to cause the thermistor to
dissipate so much energy to burn it up. OR maybe the thermistor just
went faulty and did not lower in resistance enough (after switch on) thus increasing it's
power disipation leading to burn-out.

Also, be careful.I think you are working on the mains side of the psu which
obviously requires great caution.
CAUTION:  Equipment is alive

j.frad

Alright, we got confirmation that the NTC marked R2 should be 10 OHM, we'll try replacing that and see what happens.
Thanks for the warning V9977, I'll be extra careful!
I'll keep you updated, this might happen to someone else someday and he/she will be happy to have hints for a repair.

Re: Do your Digi 192s blow their PSUs? Help me identify that thermistor!
« Reply #7 on: February 21, 2011, 06:05:22 AM »
Hi,

Same problem here, does the replacement with 10 ohm thermistor was ok ?
What replacement part did you choose ?
For 10 ohm, i can buy parts form 5100mW / 100s to 2100mW / 70s, i guess the higher the better ?

Thanks for your replies,
Best,
Thomas

j.frad

Re: Do your Digi 192s blow their PSUs? Help me identify that thermistor!
« Reply #8 on: February 21, 2011, 11:29:36 AM »
Hi!
If I remember correctly, the 10R was the only one we could lay our hands on;
But it worked.
Cheers

g9builder

Re: Do your Digi 192s blow their PSUs? Help me identify that thermistor!
« Reply #9 on: February 23, 2011, 09:28:25 AM »
Hi,

I've just picked up a second hand 192 and mine makes the funny popping noise when I turn it on too. Real glad I found this thread.

So if I swap out the thermistor all should be ok?

Any chance of a part number or where you got it from?


Cheers

Ian
« Last Edit: February 23, 2011, 09:32:25 AM by g9builder »


Re: Do your Digi 192s blow their PSUs? Help me identify that thermistor!
« Reply #10 on: February 28, 2011, 07:25:25 AM »
Hi,

Thanks for the reply, i'll post back any PB with our board.
To g9builder : i bought epcos B57237S100M (10Ohms 3100mW), you can find parts @ radiospares / farner / mouser.
I can not test the board until a week or two, so don't take my word as references...
Best,
Thomas

j.frad

Re: Do your Digi 192s blow their PSUs? Help me identify that thermistor!
« Reply #11 on: February 28, 2011, 07:46:32 AM »
Another studio had one that made a popping noise and eventually the power switch broke, so it could be that too.

Glad this thread helps! I was feeling a little desperate when we had the problem...

AudioGimmer

Re: Do your Digi 192s blow their PSUs? Help me identify that thermistor!
« Reply #12 on: February 28, 2011, 08:05:17 AM »
I believe this is a fairly common problem.

Once you hear the popping sound on switch-on, you need to sort out the thermistor, or soon enough the unit will not switch on. Of course Digi/Avid won't tell you the part number, that would be too easy. I was in the middle of a very busy time at the studio, so I had to order an advance replacement PS board and do a very quick swop over to get the system up and running in the shortest space of time.
If your 192 is popping on switch on, I'd consider leaving the whole PT rig on until you are ready to replace the part.

The Gimmer

njm

Re: Do your Digi 192s blow their PSUs? Help me identify that thermistor!
« Reply #13 on: February 28, 2011, 09:32:56 AM »
I've had this too. It's in the power on relay delay circuit. On the PSU PCB it's got the manufacturers name, I searched them on the internet, got in touch and they sent me the part for free. You can just stick a 10ohm res in there too, I replaced one a few years ago and never had any problems after.

g9builder

Re: Do your Digi 192s blow their PSUs? Help me identify that thermistor!
« Reply #14 on: February 28, 2011, 10:02:42 AM »
thanks njm!

I will take a look who it is...

Cheers


Ian


 

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