Audio Research Reference 150 - buzzing input transformer

@atmasphere

I still have the old transformer in a box over here - it seems there’s only one set of long bolts (at least those that could have been tightened).

I have been running the amp opened with the new transformer - without the top cover. I check the temperature time to time, I can touch it anytime, even after a long playtime but I can’t hold my hand on it for more than 4-5 seconds.

// I even checked with ARC, they said it was alright. Hope it lasts for long, I'm going to replace the tubes for a set of KT150's soon.

Thank you.

If it's the presence of DC, it must have happened quickly with permanent damage on the transformer. After I took it to a friend's place, it behaved the same even after plugging it into a power plant. And it would be interesting if this was the only piece of gear being damaged. My LS16 preamp works great, there's also slight buzz but I think it's normal. It's only audible when I place my ear right above the mesh cover. 

@audphile1 yes, it does sound pretty amazing 🙂

Is it expensive to replace those capacitors? I'll definitely have them checked if possible. 

Thanks, the transformer will be replaced soon. 

I'm just thinking what kind of precautions I can take so it doesn't happen again. It was quite expensive, plus shipping, custom fees and mainly, it takes time. 

I have a separated circuit for the living room sockets (not for the audio only, yet) but I'd say the power in my apartment is quite stable. 

If there's DC present it doesn't damage the traf immediately, or does it!? My guess is it can get loose but it would take some time, even weeks, right?

@jetter I have even asked the ARC if they recommend using KT150's in this model. They said definitely yes. Not in REF110 though. I was planning to get a set of KT150's when these KT120's reach their limit.  

I don't think this amp ever tasted KT150. The previous owner was a second owner and he has many amps. He said this one has been sitting in a box for some time. 

The ARC REF150 manual says that the operation temperature is about 40 degrees of Celsius. Of course the tubes are much warmer but the chassis was always about that.

@jetter Yes, we have split the new traf cost 50/50.

We're not sure how that happened. It worked fine for several hours when plugged into a cheap Dynavox filter. Then I got a proper cable that reached the wall outlet and listened for the whole evening. The buzz initiated after several hours at first. I turned it off, let it cool down, plugged it back into the filter and the buzz was still there. Maybe it was just a matter of time and it was just a coincidence that it happened after plugging it into the wall. 

Also, it was mid August, super hot weather. I placed the amp into a custom made MDF cabinet with a space of two inches on the sides, opened back, opened front, semi-opened top (there's a shelf with preamps and TT about 20 inches above). The mesh never got hot, maybe even the LS16's mesh cover gets warmer. 

I didn't really listen to it for more than an hour and half until I got the power cord.

Thanks for asking.

I'd like some advice what to check so I can listen to it with ease. 🙂 

So the traf is finally replaced. I just had a first listen. 

Does anyone know how hot the input transformer can get? I have left the cover off so I can touch the transformer. I guess it gets to about 80 degrees of Celsius after 2 hours. The output transformers are quite cool. The volume wasn't loud.

Tannoys D700's are connected at 8 ohms, bi-wired. 

It works without any problems of course, I'm still a little nervous. Thanks!