Classic-Sixty : Multiple blown fuses

[newbiec_c-j_owner]

Hello all.

As my name suggests, I'm a new conrad-johnson owner; I've been the proud owner of the classic preamp and classic-sixty amp for about eighteen months.

Recently, I had the heart-wrenching experience of my first blown fuse in my amp. I did not realize the fuse was blown until I turned on my stereo one day only to hear heavily distorted sound out of the left channel. Seeing the "fuse out" light, I quickly realized the problem, called conrad-johnson, and ordered a replacement fuse. The new fuse seemed to fix the problem completely, and the stereo played beautifully for a few hours. Just today, however, the fuse for the left channel blew again. I turned on my amp, and was allowing it to warm up before playing some music. A few minutes, later, I heard a loud pop and rushed to my stereo only to find that the fuse had blown again!

Now that the same fuse has blown a second time, within just hours of running time since it blew the first time, I suspect I have a more troubling underlying problem. I have my power run through a battery backup and a power conditioner, so I doubt it has to do with any surges. I've searched the internet for help, but can't find the advice for which I am seeking. I've read that capacitors may cause this, as can shorted vacuum tubes, but I do not know how and in what order I should check these issues.

Could somebody please either point me in the direction of some resources to diagnose the problem, or walk me through troubleshooting this?

Thank you for your help.

[admin]

First, let me welcome you to the site. Sorry to hear about your troubles. The first thing I would recommend is a close and careful inspection of the circuit boards. Look for any components that may have failed. This could include things like caps that are bulging, areas on the circuit board that look black or discolored (signs of extreme heat), loose or cold solder joints. How proficient are you with a multimeter? You can try and test individual components.

If these do not solve your problem it may need professional repair. Let us know how it turns out.

[jeffreybehr]

Is 'the fuse' a high-Voltage fuse under a largish--3/4"-diameter?--black cap perhaps on the top of the chassis or a regular-looking 120VAC fuse on the back of the amp?

[joeinid]

Bump for any amp/fuse updates? Has the problem been resolved? Was it a bad tube(s)? Something else?