Crack Speedball hpjun's trouble shooting thread [resolved]

[Paul Birkeland]

I thought I did a good job so I turned it on (my mistake for not performing resistance check). none of the boards lighted up and one of the resistors was smoking so I turned it off really quick.

This is almost always the mounting method of the TIP50C.  If improperly mounted, it could cause the problems you're describing at any given time. 

The AC wires that heat the tubes will not cause these kinds of problems unless you remove them and wire them to the incorrect location.

You'll need to carefully measure voltages for us to know what's going on.  If you have a smoking 270 Ohm resistor, you could start by measuring the voltages with just the 12AU7 installed in the amplifier and not the 6080.

 

[hpjun]

My wires heater wires was soldiered properly and terminal 12 got touched up a bit I also rewired the connectors from terminal 6,7 connecting to 9,10. It might be terminal 12 that has an issue. terminal 4 was grounded to terminal 12.

Is terminal 4 & 5 supposed to be bridged? I took off the ac heater wire and measured terminal 4 to terminal 5 and still at 0 ohms. I just want to be sure about this because I don't want to short the power supply. Also terminal 4 and 5 are both grounded. Also I read that terminal 4 & 5 is supposed to have a fluctating reading since it's connected to the caps, I get 0 ohms instead.

I also noticed the 6080 tube has something loose inside that is rattling when I shake it, is it a broken tube?

I am a little scared to turn on my amp for voltage checks. I am mostly worried about terminal 4 and 5 please answer that question.

 

[Paul Birkeland]

There are no resistance measurements in the Speedball manual for reasons like this.

When you ask about terminals 4 and 5, do you mean on the 5 lug terminal strip at the front of the chassis, or power transformer terminals 4 and 5?

 

[hpjun]

Yeah the power supply transformers 4&5. The ac heaters for the tubes.

 

[Paul Birkeland]

Yes, one end is hard grounded, and the winding itself is several turns of thick wire, so it will also read as a short to ground.

 

[hpjun]

Everything works now.

I re-soldiered my connections and took out the power tube like you said, the mini board lights up. I put the big tube back in and everything lit up, did the voltage checks and it checked out. The audio is fine, I ordered an tungsol-6080 replacement power tube it sounds better than the stock sylvania 6080.