Rega Brio - convert from 240v to 120v operation?

mrhk13

Member
2010-01-21 9:53 pm
Finally in the US with the amplifier in front of me.
The PCB is labelled ISS5.
I've tried to make sense of the schematics and @OldDIY's answer - no luck so far. I need to go a bit deeper to see how the power is connected to the windings, but if someone can give me an idiot's level description that would be great. Are there two sets of (primary) windings where for 110 V, only one set is used, but in the case of 240 V I need to connect both of them?
 

mrhk13

Member
2010-01-21 9:53 pm
Over dinner I figured out how this might be wired and opening it up completely, including the connection from mains to the primary windings confirms it. Blue and brown coming in from the wall, then black/blue to the primary winding, brown/red coming out. This way both sets of primary windings are used in parallel. To put them in series, I need to connect brown and black together, leaving blue and red where they are. This (effectively) doubles the number of windings in the primary winding, therefore reducing the 230 V EU mains to the same voltage as the 115 V US mains.

Question: is there a place where I should put the brown/black connection? I can solder them together but then they would be "floating" freely. I presume I should use some heatshrink so it's all shielded.

[IMGDEAD]https://imgur.com/a/0YMWpkW[/IMGDEAD]
 

OldDIY

Member
2009-12-16 8:23 am
Unplug from the socket! Pull out and connect (black with brown), insulate securely. First turn on through a series-connected incandescent lamp of 100 watts. If it burns dimly, everything is in order. Caution, life-threatening voltage.
 
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mrhk13

Member
2010-01-21 9:53 pm
Thank OldDIY and as_audio - that all makes sense.
I suppose I'm not a complete idiot, I have assembled some other DIY amplifiers. But since this is not something I do regularly, I tend to need a bit of time to get back into the swing of things and remind myself how it all works.
That - and I have a fundamental distrust of anything where we say current flows from + to -, whereas in reality it's the other way round :)
 

Ian Finch

Member
Paid Member
2010-04-11 4:22 am
Coffs Harbour, NSW
I'm not sure what your plan is but your mains wiring joins should be mechanically secure and screw-clamped together with US approved wire connectors. Soldering is not the way to go but don't just rely on twisting plus PVC tape or heat shrink insulation either, for your safety's sake and for the long term. There are also videos, some comprehensive and some brief, for how to proceed.
e.g Tutorial: How to crimp connectors, strip wire and use heat shrink. - YouTube
 
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mrhk13

Member
2010-01-21 9:53 pm
I wanted to circle back to this thread. I posted above asking about rewiring to go from 110 V to 240 V. I did the modification last summer, in the US, and the voltages I could measure seemed to work out (as in: half of what I had prior to the modification, when plugged in to a 110 V socket). I then shipped the amplifier to my home in Europe, where it arrived a month or so ago.
I'm happy to report it works the audio quality in the house has advanced significantly - so thank you all for your advice.
One last question: the amp does seem to run hot. The casing near where the transformer sits (I presume) is hot to the touch, almost uncomfortably so. It doesn't get hotter over time - the temperature remains constant after 15 minutes or several hours. It has been a while since I used the amp, so is this normal? Bad wiring job on my part?
 
Reference to Taps can confuse since there are four of them. On the mains primary side of the transformer to convert from 240 V to 120V operation you have to wire the windings together so these are in parallel and in the same phase. ST in the manual means start of the winding and FIN means finish ot the winding so you have to wire the two ST leads together connected to Live and the two FIN leads together to Neutral
If you get these leads in the wrong phase this will cause damage to the transformer. For 240 volts operation the windings will be in series Live ST FIN to ST FIN Neutral
 
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