Newbie need help: Voltage test did not pass - saw sparkles. (SOLVED)

[bwang29]

So I finally finished assemble my crack yesterday  . The Ohm checks were all passed. But when I'm measuring the voltage, the ones which are supposed to be 170V was over 250V, and the ones which are supposed to be 100V are below 50V. When I measured the 250V, I saw bluish sparkle light with a strike of exploding sound coming out. I did a careful check after the sparkle and it seems nothing is damaged and I stopped measuring.

The filament of the small tube does light up, while the bigger tube doesn't light up or generate heat. Only one of the two LEDs light up, the one closer to the border of the board doesn't. 

I did a careful visual check. What would be wrong most likely in this case?

[STURMJ]

Was the blue sparkle in the tube? if so that's normal for a second or two. And the crashing sound? through the head phones? that's bad, and don't plug them in during checks, I hope you didn't damage them. If the phones where not pluged in and the crash came from elsewhere,  there is also a problem.

[Paul Birkeland]

It sounds like you have the Speedball installed, is this correct?  If so, did you start with a working Crack?

~250V would indicate that the 6080 isn't drawing current, how we go about troubleshooting this depends on the above questions.

-PB

[bwang29]

I didn't expect prompt replies like this, You guys are really awesome : )

No I don't have the speedball installed yet. And the quick explosive sound is through the air, I didn't plugin headphones. I thought that's caused by some high voltage contact?

I recall some of the 0V are also above 250Vs. I'm going to buy some safety glove before keep measuring.

The 6080 tube does not generate any heat after 30 seconds and I can touch it without problem. Does this indicate something?

Also I mentioned only one of the LED is light up. Is this normal?

Thanks

[Doc B.]

An arc like that is often caused by either a missed solder connection that creates an intermittent contact, or soldered leads that should have been trimmed close to a terminal being left too long and shorting to the chassis panel. I suggest looking closely at the connection on the (unplugged) amp to see if you can find a missed solder joint, a dangling lead or a small scorched spot where the arc occurred.

[bwang29]

Thanks! It's my first time soldering. So is using too much lead for a joint or untrimmed wires a problem if they're not touching any other circuit components? For example, the manual mentioned to trim the braided two big resistors but I didn't trim them as I see they're not contacting any other part. I also cover the joint with a bit more lead than the illustration but they're all within the joint area. I made sure they all look shiny.

Also no one has answered the expected behavior of the two LEDs yet.. are they both supposed to light up?

[Doc B.]

Yes both LEDs are supposed to light up. And that is part of the reason you need to verify that all of the connections are good. If one is bad it could be causing the arcing and also be the reason that one of the LEDs is not lighting up.

We always advise that builders make their wiring look as much like the photos in the manual as possible. Untrimmed lead ends poking out of terminals are a real hazard and should be trimmed off.

I should mention that it is also possible to create a spark by accidentally touching your test probe to more than one terminal at a time when doing the voltage checks.

[Paul Birkeland]

The red/black twisted pair of wires from power transformer terminals 4/5 heats both tubes, though this pair goes to the 6080 first, then to the 12AU7.  This wiring is where you should start, as without the 6080 lighting up, there will be some problems.

Also, look at the black wire leaving the power transformer area and heading towards to the tube sockets - be sure this is connected properly or your readins will be all over the place.

-PB

[John EH]

So I finally finished assemble my crack yesterday  . The Ohm checks were all passed. But when I'm measuring the voltage, the ones which are supposed to be 170V was over 250V, and the ones which are supposed to be 100V are below 50V. When I measured the 250V, I saw bluish sparkle light with a strike of exploding sound coming out. I did a careful check after the sparkle and it seems nothing is damaged and I stopped measuring.

The filament of the small tube does light up, while the bigger tube doesn't light up or generate heat. Only one of the two LEDs light up, the one closer to the border of the board doesn't. 

I did a careful visual check. What would be wrong most likely in this case?

From your narrative I'd say maybe you caused the spark during measurement by shorting something with the meter leads or touching ground at the same time.

If I'm understand you right you have power on and no smoke and no kabooms.

If that is the case I recommend you take all your resistance measurements and voltage measurements again and post them here for the experts to look at.

Both your LED's should be lit.  The unlit one is either in backwards or not soldered well on one end probably.

John

[bwang29]

Yes, the arc was caused by shorting the meter lead and i can see some scorched dents on the lead.

So I trimmer any suspicious lead and rechecked the wiring, re-soldered any suspicious joints. Here are some of the reads I have. My DCV reader can only reads up to 250 and >250 means it goes off chart.

So the black lead touches 12.

1 100
2 >250
3 0
4 > 250
5 30
6 0
7 30
8 0
9 0
10 0
11 0
12 0
13 >250
14 0
15 >250

So I accidentally shorten the circuit while measuring 15, and burned the fuse. I'll get a new fuse and posting the rest of the reading.

[bwang29]

Any one can deduce what's going on from the reads? I'm going to drop by Radioshack and buy any components that is necessary to fix it..

[Paul Joppa]

If the 6080 is still not glowing or getting warm, then it is not getting heater power on pins 7-8. Just to be sure, is the socket oriented correctly? Some have installed it rotated 180 degrees by accident, which will Mess You Up.

[bwang29]

Ah thanks Paul Joppa!

This is exactly what happened : (

I'm going to fix the orientation tonight and see how it goes.

Do you think there is any component that's damaged by this for me to replace?

[Doc B.]

Do you think there is any component that's damaged by this for me to replace?

One step at a time. Get the socket in right, redo your tests, let us know if you have any more problems and we can go from there.

[bwang29]

Problem solved!! Crack sounds great now : ) Thank everyone for offering help here!