Audio Research Classic 60 & 120 owners


For those who own one of those, does the power transformer (left one on the 120 and the center one on the 60) get quite warm to the touch after a few hours of operation? Mine get very warm. So much so that i can hardly keep my hand on it for very long. The bias setting is dead on with SED 6550C. Mine were upgraded by GNSC back in 2004.

This is not a new phenomenon. They have been warm like this for as long as i can remember. I had meant to ask other owners but never got to it until today.
Any feedback much appreciated.
smoffatt

Showing 4 responses by sebastianloke

At last, I managed to identify the cause of the Line fuse that keeps blowing on one of the amp.

Hifigeek1 guess was correct. It is due to a faulty tube! I do not know how many were faulty as I replace all six tubes with new ones.

These replaced tubes were less than 100 hours of use. It just shows new tubes can be faulty at times.

I do not have a tube tester. Can anyone suggest how I can find out which one is faulty from the six I have taken out?

Thanks
Many apologies for the delay in replying. I have not logon here for awhile. I live in London, UK.
Hello, I am new to this site and hope some of your members here can assist me.

I have been using a pair of Audio Research Classic 120 for about 18 months now. This is my first valve amp and I am delighted with the superior sound quality it has over all my previous transistor amps I have owned over the years. My last amp was a Musical Fidelity A370.

The only problem I have is, one of the amp's line fuse keeps blowing! This is a slow blow, 250 VAC, 3 amp fuse. Can anyone tell me why? Anyone have similar experiences?

The engineer has given up hope in finding the fault! It happens happens intermittently. Sometimes, it will work for a few hours or days. Sometimes, it will blow immediately after switching on! This also happens on the engineer's test bench. He could not locate the exact problem as it works at times but not the rest of the time.

The engineer has replaced the rectifiers, all 12 caps (450v/ 800uF) and 16 x 6550 tubes on both amp.

I am using this power amp with Audio Research Pre-Amp, LS-2 and the Apogee Hybrid Ribbon Speakers, Centaur Major.

Your help and advice is most appreciated. Thanks
Many thanks for sharing your thoughts and advice.

I will check the tubes as suggested by Hifigeek1 and will also check the tubes are operating with a bais of .65mv as suggested by Smoffatt.

Hifigeek1 could be right regarding a faulty tube (despite the tubes are new with less than 100 hours usage). Next, I will check on the socket as suggested.

Last week, ARC technician did suggest I should swap the tubes from the working Amp to the Amp that I am having problem with the blown fuse. After swapping and if the fuse still blows, then I should try swapping the caps from the good amp to the bad amp. I hope this will narrow down the uncertainty of tubes or caps being faulty.

I will report back with my progress. Wish me luck and keep your suggestion coming!