Audio Research VS110 Middle transformer gets very hot the 2 sides not so is this normal

What are your speakers?  How loud are you pushing it?

Martin Logan sl 3
just loud enough to here all the music 
about 9 o’clock on pre amp which starts out at 7 o’clock 

That middle transformer is the power tranny. And all the incoming AC and current is going through it! So naturally it is going to heat up the longer your amp is in use! And if your speaker load tends to be 4 ohms or less, then that power tranny will get even hotter! The best solution is to replace it with a bigger transformer rated for more current. But a bigger transformer won't fit in that amp's chassis!

Poor design from Audio Research! Chassis and power tranny too small for rated power! 

Those Martin Logan electrostats have an impedance that falls to 1 ohm at high frequencies! A disaster for most tube amps. Try a big class A Krell or Pass amp instead!

Stop using that ARC amp when the power tranny starts getting hot! Otherwise you will end up with a dead transformer with melted windings (insulation)!

 Unless the middle transformer is getting really hot I would not worry. If you can touch the top you should be OK. The middle transformer is the power transformer for both channels while the other two transformers are channel specific. Notice how much bigger it is. You can email Audio Research and ask them if they think there is a problem for peace of mind.

  The SL3s are excellent speakers. The VS110 should have no problem driving them. I drove a pair of SL3s for years with a Classic 60 and then V70. I even had them for a short while with my current Ref 110. I finally replaced them with a pair of Sonus Faber Elipsa SE speakers.

If no red plating tubes, most likely nothing to worry about.

It certainly isn't a bad design from ARC!

I used the VS110 to power Maggie 3.6R's and never had the middle transformer get that hot. Those Maggies were rated 4 ohms - with the tweeter drawing 3.3 ohms. The VS 110 drove them with ease.

Your SL3's are even more sensitive than my old Maggies - 89 compared to 86, so it's not a power handling issue. I wonder if there's an issue with the middle trans specifically? @lostbears has a point in terms of emailing ARC.

$10 infrared sensing handheld electronic thermometer.

Point it at the transformer, on different areas of the transformer, and you’ll get a reading.

From this you can guess the transformer core temperature, as you are measuring it’s surface temp (which will be different). The numbers measured will be all over the place but will have an average.

This will tell you all you need to know, in order to get the answer you seem to be asking for.

I was told a long time ago that if the power transformer gets hot but the other transformers remain cool then it's a good tube amp design.

That can be sort of true, yes.
But peace of mind is only a $10 electronic infrared thermometer away...

I expect to hear back a number of 50C or thereabouts. Not the exact correct number, as there never really is one - but simply a range, depending on the design.

Thanks to all above I certainly will consider  all advice 

I have another question if you don’t mind as I am new to tubs 
the right speaker is louder than the left ( not by a crazy amount) but currently there nevertheless 
would this be an amp issue - prep amp issue  or speaker issue 

I will switch the right & left speakers to see if it a speaker issue 
but how would you distinguish between the amp & pre amp 
 
 

molocka12

the right speaker is louder than the left ( not by a crazy amount) but currently there nevertheless
would this be an amp issue - prep amp issue  or speaker issue
I will switch the right & left speakers to see if it a speaker issue
but how would you distinguish between the amp & pre amp

You can use the same technique. Take the preamp outputs and reverse the left and right into the amplifier inputs. If the right speaker remains louder than the left, you'll know the problem isn't with the preamplifier.

For those who analogize a garden hoses with cables...
this seems to me apropos....
My 74' Kawasaki H2 mkll's (750 two-stroke triple) center cylinder got hotter as well!