Sunn model T popping breaker?

[thehornedone]

Any idea what could be wrong with a model T if when you turn it on it immediately pops a breaker?

[Isaac]

I'd suspect a bad power transformer or filter capacitor. Hope it's the cap.

[loudthud]

Does it make any difference which position the Standby switch is in?

[mike_sims]

most likely the filter cap. the transformers on these things are nearly bullet proof unless of course you did something extremely wrong

[Ryanx]

have a tech check the soldering jobs leading out from your caps.  if you had a botched solder, it could give you this effect.  i ran into this problem personally.

[mike_sims]

solder.. for something that appears so simple, can also present a bunch of hidden problems.. i know this from working on pedals.

[thehornedone]

Thanks for the suggestions.  I'm hoping it's the filter cap.  I won the broken one on eBay if anyone else saw it. I ordered all the caps that might need replacing, including the filter cap for 60 bucks from tubesandmore.com.  The guy said he never took it to a tech, so I'm guessing it's an easy fix. Worse case is the power transformer, and mercury magnetics clones those for 300 bucks...so, not the end of the world.

Another possibility is one of the rectifier diodes.  This thread details an issue a guy had with a blown diode:

http://music-electronics-forum.com/t14222/

It also has a great step-by-step troubleshooting guide for the model t. Truly a great reference for anyone who is having issues with theirs.

I'll update this thread when I figure out the issue as a reference for anyone else who is popping fuses.

[thehornedone]

Does it make any difference which position the Standby switch is in?

Don't know yet, but we'll see once it gets delivered.

[CONAN)))]

I had this with a Sunn Beta and it was a bridge rectifier in the mains output.

[EdBass]

I had this with a Sunn Beta and it was a bridge rectifier in the mains output.

I'm the first to admit that I'm not the most transistor Sunn knowledgable person, but what on earth is a bridge rectifier doing in the mains output? 

I would imagine that could indeed cause a problem.

[mckinnon audio]

   Hi there,sounds to me like our friend is British,hence the reference to the "mains",or AC as we call it. So he's saying the bridge rectifier is at the output of the AC stage,and he's right. Mel.

[thehornedone]

Well, good new guys: I got the amp today. Replaced the caps straight away, cleaned the pots, plugged her in and *PHEW* it powers on and the tubes light up.  I set the bias, plug it up, and it works perfectly! The part that took me the longest was getting the chassis back in the damn headshell. Every time I went to line the screws up and push down to screw them in, they would pop out these little nut things that clip into the chassis on the inside...major pain in the ass. I finally bent them all enough that they would stay in. 

So, thanks everyone for your pointers, I'm pretty sure it was the power filter cap that was the issue. My multimeter doesn't measure capacitance, otherwise I'd test to see how low its operating.

[thehornedone]

And, by the way, the power filter cap in the model t already has a drain-down resistor between the + and -. When you turn it off stand-bye, and then turn the power off, you hear the sound come back in and fade out. That's the power filter cap draining. It should technically be safe to work on within a couple hours of it being turned on without draining that filter cap specifically. There are two other smaller ones that do not have a resistor across them.