Hello all.
I've made a mistake and connect the preamp ( Rotel RC 1070) to 220V, smoke...
I have dismantling the unit, and try to wire the other 115V part of the transformer..smoke.
As i'm a neophite, i have a dream, and maybe i've blown an internal fuse...and the transformer is not dead.😡
the main fuses (3) are after the transformer, so no fuses between the mains and the transformer.
The secondary values of the transformer are 19V-0-19, and 11V-0 ( i have read that on the web)
Some knows where i can find a replacement?, i've searched, and ...nothing. Any tip?
Here, diagram, and picture of the beast.
Thanks for your opinions!!
Fabian
I've made a mistake and connect the preamp ( Rotel RC 1070) to 220V, smoke...
I have dismantling the unit, and try to wire the other 115V part of the transformer..smoke.
As i'm a neophite, i have a dream, and maybe i've blown an internal fuse...and the transformer is not dead.😡
the main fuses (3) are after the transformer, so no fuses between the mains and the transformer.
The secondary values of the transformer are 19V-0-19, and 11V-0 ( i have read that on the web)
Some knows where i can find a replacement?, i've searched, and ...nothing. Any tip?
Here, diagram, and picture of the beast.
Thanks for your opinions!!
Fabian
Attachments
Hi, ok:
outputs:
Black and one red ( 19V)>: 3,6 ohm
Black and the other red (19V): 3.6 ohm
brown and blue ( 11V) 3.8 ohm
inputs:
white and orange: nothing
white and blue: nothing
orange and blue: 3.6 ohm
What does it means?
outputs:
Black and one red ( 19V)>: 3,6 ohm
Black and the other red (19V): 3.6 ohm
brown and blue ( 11V) 3.8 ohm
inputs:
white and orange: nothing
white and blue: nothing
orange and blue: 3.6 ohm
What does it means?
Could be a bad situation there with smoke, but you could also find a suitable replacement, or custom order one. Also, detach the fuses and see if there's any problem or load.
S
S
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Basic electronic wisdom : When you let the smoke out of things, they stop working.
If you've gotten smoke out of that transformer, it's done. The odds are that heat has melted the enamel insulation on the windings and it's either shorted or fused.
For electrical safety, you need to replace it.
But usually a transformer survives connecting to 230V mains while being wired to 115V... But the components that are connected to the transformer are likely death... They got extremely more than the voltage they were specified for.
Maybe you could show us some good photos and detailphotos of the board yust to say if you're riding a death horse now.
Maybe you could show us some good photos and detailphotos of the board yust to say if you're riding a death horse now.
I have mistakenly powered at the wrong voltage a few devices myself. A few seconds at most are enough to hopelessy destroy a small transformer like yours. The low primary ohmic reading means that the primary is melted and shorted. A thermal fuse is only fitted on bigger transformers, and it would have resulted in a open reading (and no smoke). If the original spare part is difficult to source, and you have some time to spare, I believe that a standard 18+18V toroid would be good enough. The 11V secondary should be about 50 turns only. According to your ohmeter readings, it may still be good. You may try to recover the 11V winding wire from the burned transformer and wind it manually around the new toroid.
hi NFS, here we go!
take a look.
I don't know if the power on relais is free, may be i need to open it and see..
take a look.
I don't know if the power on relais is free, may be i need to open it and see..
Attachments
Pcan, i got it.
How is the procedure to wind it manualy?
i start where?, soldering to a 18V output and start winding the 50 turns, or whetever the lenght give me?
How is the procedure to wind it manualy?
i start where?, soldering to a 18V output and start winding the 50 turns, or whetever the lenght give me?
Ok, i have news.
Dismantling the transfo, i've seen a termal cut off that's of course off.
So now if i baypass the cutoff when i measure i have:
white and the blue 4.5 ohm
white and orange: 9 ohm
does it means something?
Dismantling the transfo, i've seen a termal cut off that's of course off.
So now if i baypass the cutoff when i measure i have:
white and the blue 4.5 ohm
white and orange: 9 ohm
does it means something?
ok, last try, and all is shorted as you adviced.
Tomorrow i'll have a standard transformer with the correct values ( waiting for the torroidal), i know it's not a torroidal, but i'll be a good experiment, just to see if all the othe stuff works ok, and how this preamp behaves.
More pictures tomorrow.
Thanks!!
Tomorrow i'll have a standard transformer with the correct values ( waiting for the torroidal), i know it's not a torroidal, but i'll be a good experiment, just to see if all the othe stuff works ok, and how this preamp behaves.
More pictures tomorrow.
Thanks!!
Before you connect new transformer, measure resistance of each winding. Unconnected. So you have reference.
Wind a few turns say 20. Measure Voltage. So 20 gives say, 1V You need 20*11 for the 11V. Don't connect the beginning lead wire to the other windings Yet, if You wound backwards You'll probably need to reverse the the leads. After winding connect one lead to the end of the original. Measure. Voltage reduced ? Reverse leads. As the pre-amp has 2 supplies, there will be probably a point on the circuit (Ground ??) where the two supply circuits connect. I would also put a non conductive, insulating tape or transformer "carton" before winding. On a PA I own I have used medical adhesive tape. Check temps.
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Hello all.
Well, today I received a new transformer, not toroidal.
It was designed for 19V-0-19V, 11V-0.
500 ma
220V
I bring the dead toroidal, they take the cable diameter measurements, and when i mention I was worried about the hum in my preamplifier, the guy mentioned that they ad a foil in the middle between primary and secondary ( ? a I done remember exactly) and this foil is grounded.
Same way that isolation transformer, he said.
Well, today I receive it, I mounted it without modifications of the cabinet, just in case I need a toroidal..just to test.
measurements, on: 19V and 11 sharp.
I turn it on, perfect...
then the amp, and.........dead quiet. no hum, nothing.
I was very surprised.
And happy.
So problem solved.
here some pictures.
thanks all for your support!!
Fabian
Well, today I received a new transformer, not toroidal.
It was designed for 19V-0-19V, 11V-0.
500 ma
220V
I bring the dead toroidal, they take the cable diameter measurements, and when i mention I was worried about the hum in my preamplifier, the guy mentioned that they ad a foil in the middle between primary and secondary ( ? a I done remember exactly) and this foil is grounded.
Same way that isolation transformer, he said.
Well, today I receive it, I mounted it without modifications of the cabinet, just in case I need a toroidal..just to test.
measurements, on: 19V and 11 sharp.
I turn it on, perfect...
then the amp, and.........dead quiet. no hum, nothing.
I was very surprised.
And happy.
So problem solved.
here some pictures.
thanks all for your support!!
Fabian
Attachments
Great result - I would also thank the guy who sold the replacement transformer to you, just for making a special type like this and for his advice. Many owners would trash their audio gear when the transformer fails but you persisted - good for you 😉
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That's a nice transformer. It is wound in the old fashioned way, not up to modern electrical standards but good quality, as you noticed. You have been lucky because the original one failed so fast, that the power supply regulators had no time to overheat and fail. To get hand-made custom replacement transformers for vintage devices I have to wait for weeks and pay a hefty price, and therefore I usually try to modify a standard part at first. Rewinding a small transformer was once a standard job, but today few shops still are in this business in my country. The rewinder local to my town has become an industrial operation that only reworks big motors and transformers. I bet that on most western countries the situation is the same.
