Overheating power trafo in G9 ?
« on: October 26, 2004, 03:27:39 PM »
Hi all

Last week the bass player of my band came to me and we worked on a new song in my little studio. We always play a riff and then work on the drum parts for this riff just to give our drummer a guide line. This means we track guitars and then doing drum programming and then tracking guitars and so on. As i used the G9 as the mic preamp for guitar tracking the unit was on several hours (my guess is 3-4 hours).
After doing some drum tracks we wanted to continue tracking guitars as i noticed that there was no signal in cubase. Looking in the rack i noticed that the LED of the G9 was out. So i checked the power cable but it was correctly plugged in.
I unmounted the G9 and opened it up. First thing i noticed that the fuse was destroyed. The glass body of the fuse was completely black from the inside, not just the small wire inside broken.
I investigated further and then noticed that there was a big heat around the transformers. So big that the foil around one of the torodial transformers was already melted on some places. Looking and touching around i found out that it only was one transformer, the one that transforms the incoming 230V to 12V.

Testing the unit with a new fuse revealed that the transformers seems to be fried. The new fuse blew immediately. At one place of the transformer it seems that the wires broke (could this be happening because of heat/too much power drain ?)

So now i am sitting here wondering what went wrong. I haven't found any other areas where a fault could have been happened. For me it really seems that the power transformer simply overheated over the time and was destroyed. Granted i never left the G9 on for such a long time, normally only around half an hour.

As suggested i used 2x 30VA transformers. Now as i need a new one i am wondering if i should by a 50VA transformer for the 230V-12V transformation.
Anybody had similar experience ? Anybody left the G9 on for several hours without problems ?

I just want to be sure what the problem is and not wanting the new transformer to get fried again.

As always thanks

Flo


mcs

Overheating power trafo in G9 ?
« Reply #1 on: October 26, 2004, 04:44:22 PM »
How well is the box ventilated? Are you sure there are no shorts anywhere? I guess the transformer didn't have a thermal fuse built-in...

Best regards,

Mikkel C. Simonsen

Kev

Overheating power trafo in G9 ?
« Reply #2 on: October 26, 2004, 04:47:19 PM »
I used my G9 for a recording session last year.
It remained on for 9 days straight ... centred in the rack with no air between gear ... ambient temp was probably 25 - 30 deg C.

hey I'm about to start the next recording for the same guys ... this time not in a Mud Brick House but a House built of STRAW and then bagged and rendered.  I'm taking leave again for a week (22 to 26 nov).  I have one song left to mix from last years recording.  So we should be able to release soon and coincide with the summer shows.

I'll use the G9 again and probably back it up with the Great River.  May do some testing with project 2 based Melcors and JLM99v's ... perhaps I'll test some others but I don't like doing too much testing while recording.
Kev
DIY Factory

PRR

Overheating power trafo in G9 ?
« Reply #3 on: October 26, 2004, 06:02:46 PM »
Blackened fuse suggests a dead-short. It could be the transformer, but rectifiers and power capacitors also fail dead-short.

Disconnect the transformer from the rectifiers. Re-fuse and power-up. Does the fuse blow? If not, then connect the rectifier but disconnect it from the caps, and try again. Eventually you will find what part shorted.

CJ

Overheating power trafo in G9 ?
« Reply #4 on: October 26, 2004, 06:23:22 PM »
You know about not using a bolt that goes thru the center if the transformer and back around to the chassis, right?
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

Ian MacGregor

    Echo Park, Los Angeles, CA, USA
  • Posts: 280
Overheating power trafo in G9 ?
« Reply #5 on: October 26, 2004, 06:47:30 PM »
Quote from: "cjenrick"
You know about not using a bolt that goes thru the center if the transformer and back around to the chassis, right?


Ok, I have seen this mentioned on a couple threads. How the hell are you supposed to mount a toroid if you cant use a bolt through the middle??

Ian
www.blackwatchsound.com
www.standard-audio.com
 ------------------------------

mcs

Overheating power trafo in G9 ?
« Reply #6 on: October 26, 2004, 06:50:32 PM »
Quote from: "Ian MacGregor"
Ok, I have seen this mentioned on a couple threads. How the hell are you supposed to mount a toroid if you cant use a bolt through the middle??

Only one end of the bolt should touch the chassis - not both ends.

Best regards,

Mikkel C. Simonsen

louder

Overheating power trafo in G9 ?
« Reply #7 on: October 26, 2004, 07:02:30 PM »
alo
i have a g9,and every time i use it,it`s on for several hours,with no prob.
only for once,it stoped working,because(stupid me)i did not ventilated the box,with some holes.
when it stoped working,nothing burned,only the heather`s volts went around 1volt.
hope you get g9 fine.
best regards
pedro

robomatique

Overheating power trafo in G9 ?
« Reply #8 on: October 26, 2004, 07:25:06 PM »
Quote from: "mcs"
Quote from: "Ian MacGregor"
Ok, I have seen this mentioned on a couple threads. How the hell are you supposed to mount a toroid if you cant use a bolt through the middle??

Only one end of the bolt should touch the chassis - not both ends.

Best regards,

Mikkel C. Simonsen


Could I mount the toroids on top of each other, as long as the bolt doesn't touch both ends?

Robert
"Trying is the first step towards failure."
-H. Simpson

BYacey

    Where dogs wear thermal underwear, Alberta, Canada
  • Posts: 769
Overheating power trafo in G9 ?
« Reply #9 on: October 26, 2004, 09:36:05 PM »
Stacking torroids isn't a good idea either. If they share a common mounting bolt through the middle you have now coupled the two transformers together through the magnetic field. If the phasing is wrong between the two cores this could produce some heat as well. Best idea is to use a large nylon bolt made for this purpose and bolt the torroids down individually.
Bill Yacey
"Adjust R116 for least smoke"


gyraf

Overheating power trafo in G9 ?
« Reply #10 on: October 27, 2004, 03:04:43 AM »
Naa,

Stacking the toroids is actually a good idea sometimes, IMHO. As long as the mounting bolt is only connected in one end, there is no magnetic coupling between the two (magnetic field is at a right angle to electric field), and mounting them out-of-phase allows you to control hum radiation quite well in sensitive equipment (although it takes some experimenting)

Quote
Could I mount the toroids on top of each other, as long as the bolt doesn't touch both ends?


Yes. This is how toroids are ment to be mounted. If you keep the top of the bolt clear, there will be no problems.

Jakob E.
..note to self: don't let Harman run your company..

Overheating power trafo in G9 ?
« Reply #11 on: October 27, 2004, 08:53:20 AM »
First thanks for all the answers.

Well i am not sure if there are any shorts but until the moment the trafo died everything worked fine. The case itself isn't ventilated very well. But then shouldn't be both transformers be too warm? It was clearly only one, the other was normal. I guess i will drill some ventilation holes in the case, won't hurt anything.

PRR thanks for the suggestions. As soon as i find time, i will try this.

Yes i paid attention that the bolt that holds the transformers (both stacked and holded by one bolt) doesn't touch the case on the other side.  So this shouldn't be the problem.

Thanks again

Flo

Overheating power trafo in G9 ?
« Reply #12 on: January 17, 2005, 04:03:10 PM »
Well it took quite some time but today i received an order with some torodial transformers and amongst them the replacement for the destroyed G9 trafo. I hooked it up and so far the G9 is running 4 hours straight without problems. The transformer is a bit warm but it's no problem touching it.
Seems like the old trafo was of bad quality.

Just wanted to update this since it's in the meta thread and somebody researching the G9 should see this.

Flo

Bad trafo
« Reply #13 on: January 18, 2005, 02:09:55 AM »
Excellent Information

Does anyone know about power transformers containing a screen wire. How where these designed to be used. Is it grounded to chassis or a floating ground. Transfomer sketch below...



I had a similar heat incident where I hooked the screen on a power trafo (115 to 24V) to chassis ground and monitored it. It started to get a bit hot so I disconnected it and left the screen wire as a no connection. It then ran fine from then on with a slight warm to the touch temperature. I left the screen wire un-connected and never fiddled with it again. But I feel like the screen wire was still supposed to be used somehow, I just never spent time to figure it out until now.

gyraf

Overheating power trafo in G9 ?
« Reply #14 on: January 18, 2005, 03:44:23 AM »
Transformer inter-winding screen is ment to go to ground - it is a protective measure, insuring that your mains voltage won't reach your low-voltage circuits (without first being grounded, that is).

When you have this option, always connect it to ground/chassis.

If the transformer heats up considerably with this connection grounded, there is something very wrong with the transformer! I wouldn't like to use a transformer with those symptoms..

Jakob E.
..note to self: don't let Harman run your company..


 

Related Topics

  Subject / Started by Replies Last post
40 Replies
6154 Views
Last post January 28, 2007, 12:44:44 PM
by Purusha
1 Replies
999 Views
Last post September 12, 2008, 10:51:05 AM
by Kamel
0 Replies
1035 Views
Last post September 04, 2011, 11:16:32 PM
by Mbira
47 Replies
1541 Views
Last post July 04, 2018, 07:45:36 PM
by scott2000