Hello.
I have a NAD 3130 with primare dead transformer.
Can any help me with voltage of this transformer,any information on service manual.
Thanks.
SM
Download NAD 3130 Service Manual | ManualsLib
I have a NAD 3130 with primare dead transformer.
Can any help me with voltage of this transformer,any information on service manual.
Thanks.
SM
Download NAD 3130 Service Manual | ManualsLib
After some more investigating, I've learned the same or similar transformer is used in the 7130 and 7140. Looking at the schematics the input circuits look the same.
So now I have the output voltages of the transformer and the max currents based on the rectifier ratings... Now what? Is this enough information to source an alternate transformer? How do I figure out the impedance ratings
So now I have the output voltages of the transformer and the max currents based on the rectifier ratings... Now what? Is this enough information to source an alternate transformer? How do I figure out the impedance ratings
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Check if there is a thermal fuse broken in the dead transformer. That is easy to repair. Often to find under the first layer of protective wrapping. In series with the primary coil.
What is dead with the old transformer? Primary or secundary?
If the specs and the sizes of your alternatives are close to the original, you can give it a try.
If the specs and the sizes of your alternatives are close to the original, you can give it a try.
Thinner wires then the secondaries, and often with a very good hidden thermal fuse. Pry it open. Otherwise buy a transformer close to the original specs.
You asked about impedance ratings --
https://community.ptc.com/sejnu66972/attachments/sejnu66972/PTCMathcad/176415/1/Table...
https://community.ptc.com/sejnu66972/attachments/sejnu66972/PTCMathcad/176415/1/Table...
You might find it easier to buy two transformers, one for each secondary.
Multi secondary transformers are often custom made.
Unless you can source an original that is.
Multi secondary transformers are often custom made.
Unless you can source an original that is.
I understand that impedance could be an issue if you changed from a relatively high to low impedance transformer type - usually just by substituting a toroidal for the original E-I laminated type. I'm not sure your reference to the suggested specs. of 60Hz mains distribution monsters from 2.5 kVA up is going to say as much here, tbh.
I've seldom seen impedance even mentioned on datasheets that cover stock transformers suitable for small, solid state audio amplifiers, whether E-I laminated or toroidal - even 1kVA and larger. I think it would be more practical to just say; use a similar, under-rated E-I type that fits and would also suit any NAD with 2N3055/MJ2955 output transistors (like just about all the early models 🙄). So, my source for NAD transformers has just been another NAD 3020 series wreck (noting the switched secondary winding necessary for 4R loads).
There are still plenty of these amps around after the DIY "fixers" have hacked and messed with them. Its just a pity that some NAD worshippers think a dead and/or badly hacked amplifier is worth as much as a pristine, fully working one and pay up accordingly... 😛
Congratulations 🙂
If you hadn´t:
schematic clearly shows 23+23VAC for low impedance loads, or 28+28VAC for high impedance ones.
A good feature other manufacturers should copy.
Plan B and to simplify your life would have been to decide beforehand what speaker impedance you will actually use and buy a standard transformer with the proper voltage specs.
VA rating should be 1.5X to 2X the full (2 channels driven) RMS power rating.
Voila! Now you know for the next time 🙂
If you hadn´t:
schematic clearly shows 23+23VAC for low impedance loads, or 28+28VAC for high impedance ones.
A good feature other manufacturers should copy.
Plan B and to simplify your life would have been to decide beforehand what speaker impedance you will actually use and buy a standard transformer with the proper voltage specs.
VA rating should be 1.5X to 2X the full (2 channels driven) RMS power rating.
Voila! Now you know for the next time 🙂
Nice to know if/when needed but NOT what the OP asked 🙂
Same thing.
The OP is not asking about a transformer parameter known as (internal/own) impedance but a NAD amplifiers feature: they have a *dual secondary voltage* power transformer, switch selectable by the user, so they deliver about same power output on 8 or 4 ohm speaker impedance loads.
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True, as I also mentioned at line 5 in my post. To complicate the matter, the transformer is smaller than you may expect for a 30WPC stereo amplifier. It's supply voltages sag a lot under load which actually protects the output stage for no cost at all. However, it also reinforces the need to reduce the supply voltages with nominal 4R loads. Perhaps failure to do that is what caused the transformer to overheat and burn in the first place.
Modern hifi speakers with a nominal 8R rating are lower now, more like 6R rating and 4R speakers more like 3R. That suits speaker manufacturers trying to increase perceived volume levels but probably adds to the problems for old designs like the NAD 3020 in its many variations like this one.
Modern hifi speakers with a nominal 8R rating are lower now, more like 6R rating and 4R speakers more like 3R. That suits speaker manufacturers trying to increase perceived volume levels but probably adds to the problems for old designs like the NAD 3020 in its many variations like this one.
