Genelec 1031a Mains Transformer open primary

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oldskool1

Active member
Joined
Oct 12, 2021
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35
Location
Los Angeles
The primary windings on the big beefy 100-3103 toroid transformer in one of my Genelec 1031a have gone open. This type of failure is new to me... I don't think I've ever seen the primaries on a large transformer like this one go open. Is this something anyone else has seen?
 
I never had that problem with the 1031.
That transformer can be Re-winded...
Re-winding transformers is also new to me. I googled it and I came up with this:
https://www.t-r.com/view.php?pg=rewindI wonder if one of those will fit in my 1031a? ;-D
The transformer in the 1031a is a complex toroid with 2 primaries and 2 different secondaries... I don't think that it can be cost effectively re-wound. But please provide a link if you have one.

I think it will be easier and cheaper to replace the transformer with one or two transformers, because there is a lot of space in that cabinet. I have nine 1031a's, and since the 90's this one is the only one that has failed numerous times. None of the others have ever failed.
 
I don't have a link,
I have a local guy around here that Rewinds transformers for a Living.
He is able to Rewind standard Ei lam transformers but also Toroid transformers, I always use him when I have a burned transformer.

Well sometimes if the transformer is small I Re-Wind it myself
 
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It could be an internal thermal fuse that opened up.
That would be my first guess... The fuse is not buried very deep in the transformer. Simply unwind the outer windings until you reach the inline fuse, replace and rewind. It's about as difficult as sowing a button to a shirt, but you will have to be patient, it takes (a lot) of time. A new transformer is still available as replacement part...

Fuses however, open for a reason, better find the reason before you plug it in again :p
1) external: intermittent connection to mains (check cables, wall outlet, etc.) or overvoltage
2) internal: Genelec uses quality components, but given their age and the heat buildup, some of the caps will have dried out.
 
The most common issues I found when servicing these speakers were blown Electrolytic capacitors in the power rails.
Maybe that was the reason for the blown primary in the transformer, being it a Shot winding or shot TX internal fuse
 
The most common issues I found when servicing these speakers were blown Electrolytic capacitors in the power rails.
Maybe that was the reason for the blown primary in the transformer, being it a Shot winding or shot TX internal fuse
Rectifiers diodes fail short circuit from overheating. A shorted PS diode can try to drive AC into a reservoir capacitor drawing excessive current that can overheat/blow out capacitors and damage the transformer.

JR
 
Thanks for all the ideas everyone. I'm going to try to find out what the reason for the failure is, and also attempt to unwind the transformer to expose the fuse, but I don't know if I'll be successful in rebuilding it, seeing as I've never done that before. Jim at Genelec service is kind enough to sell a replacement transformer at $201, but I want to find the cause of failure first because that's a lot of money to put into such an old speaker.
 
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That would be my first guess... The fuse is not buried very deep in the transformer. Simply unwind the outer windings until you reach the inline fuse, replace and rewind. It's about as difficult as sowing a button to a shirt, but you will have to be patient, it takes (a lot) of time. A new transformer is still available as replacement part...

Fuses however, open for a reason, better find the reason before you plug it in again :p
1) external: intermittent connection to mains (check cables, wall outlet, etc.) or overvoltage
2) internal: Genelec uses quality components, but given their age and the heat buildup, some of the caps will have dried out.
Never had a tranny issue with Genelec 1031, or any Genelec in 20+ years. Caps, drivers, mechanical rattling, cold-solder joints, falling on console damage, etc. yes
There is no fuse wrapped-up in the transformer. Genelec would never design something like that. No one has ever designed anything like that.
If you really have infinite ohms at the primary leads of the disconnected from anything else transformer, get a new transformer from Genelec. They will probably want to check it themselves as it is an anomaly.
Mike
 
Never had a tranny issue with Genelec 1031, or any Genelec in 20+ years. Caps, drivers, mechanical rattling, cold-solder joints, falling on console damage, etc. yes
There is no fuse wrapped-up in the transformer. Genelec would never design something like that. No one has ever designed anything like that.
Where do you think transformer thermal fuses are?
If you really have infinite ohms at the primary leads of the disconnected from anything else transformer, get a new transformer from Genelec.
Internal transformer thermal fuses are not user serviceable parts... replace the transformer or get it rebuilt by a professional.

JR
They will probably want to check it themselves as it is an anomaly.
Mike
 
Jim from Genelec Service confirmed that there is a thermal switch inside the transformer. He said that if it's a "small spike" the switch will close again after a while, but if it's a big spike then "the transformer is gone". He told me to get a surge protector. I do think that the unit failed when the power switch happened to be on and I plugged it in... I think that the IEC cable made contact briefly several times before being fully plugged in and these current surges wreaked havoc in the transformer. Oh well, a $200 lesson on how not to plug things in...
 
Jim from Genelec Service confirmed that there is a thermal switch inside the transformer. He said that if it's a "small spike" the switch will close again after a while, but if it's a big spike then "the transformer is gone". He told me to get a surge protector. I do think that the unit failed when the power switch happened to be on and I plugged it in... I think that the IEC cable made contact briefly several times before being fully plugged in and these current surges wreaked havoc in the transformer. Oh well, a $200 lesson on how not to plug things in...
Thermal fuses inside transformers are generally not fast blow fuses, but slow blow from heat buildup over time. PTC will generally go high impedance and stop heating. These thermal fuses are still fuses so it is possible break them with a large enough transient inrush current, but prudent design sizes them to work as intended, more often than not.

WRT DIY repairs, you void any warranty or safety agency approval.

JR
 
Thanks for posting the Ebay link moamps! Following your lead I was able to find the transformer with the exact same specs as the Genelec:

https://www.ebay.com/itm/252435820016?hash=item3ac658edf0:g:Q5MAAOSw14xWNi4F
The only problem is that none of these transformers fit inside the speaker. They are all much larger than the original. I thought about mounting it outside, but then it would cover up the power switch and IEC inlet unless I drill another mounting hole. Not to mention having to wire up new Molex connectors... I think I'm going to order the original part.
 
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