Testing lead 2 threw a bright blue spark and burnt a white capacitor

J

jlsmithseven

New member
So I just built  my first amp ever the bottle head crack. Tested ohms everything went great. Put my alligator clip on lead 2 upper and a bright blue spark threw and scared me and I jumped and took it off the lead. Somehow I found the nerve to continue testing the others just by pressing it against the tabs and they all checked good. Now there’s a burnt mark on the white long rectangle block capacitors and I wanted to sell this eventually. I have the speedball kit to put in yet but to be honest I’m scared now. Will my heart health be affected by this shock? I kept my left hand in my pocket and wore rubber shoes.
 
You're good for another day assuming you were not in a coma when you wrote your message. It's scary, but most often harmless.
 
What do you mean good for another day? I think the alligator clip sagged and touched another terminal , I let go of it and I unclipped it then. Apparently this is common I guess I just don’t feel comfortable with it
 
The alligator clip needs to go on the black meter probe and to a ground terminal.

Do not use an alligator clip on the red probe.  You just need to touch the red probe to each terminal to measure them.  If you want to use an alligator clip, you would need to power down the amp and wait five minutes between reading the voltage of each terminal.
 
jlsmithseven said:
Put my alligator clip on lead 2 upper and a bright blue spark threw and scared me and I jumped and took it off the lead.
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Are you using alligator test leads, or just an alligator clip that you then touch with the probe?  Either way, consider getting some minigrabber leads like this (no affiliation): http://www.amazon.com/gp/product/B0002JJU3C/ref=ox_sc_act_title_1?smid=ATVPDKIKX0DER&psc=1  They have little spring-loaded grabber hooks that retract when not clipped around something. With these you don't need to keep a hand on the probe - just securely connect (magnifier glasses come in handy here), let go and look at the meter for the reading.

Somehow I found the nerve to continue testing the others just by pressing it against the tabs and they all checked good.
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Congrats! You've got an amp that's passed its resistance and voltage checks.

Now there’s a burnt mark on the white long rectangle block capacitors and I wanted to sell this eventually.
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I think you're probably referring to one of the two large 10W 3K resistors that are close to the terminal you were measuring. You could post a pic of the amp, including a clear shot of the burn mark.  Sounds like there was definitely a short somewhere - might have been from the clip, or could have been caused by an errant clipped lead that was sitting somewhere it shouldn't have been -- or even an attached lead end that needs trimming. If the burn mark is permanent and that bothers you, the big white resistors are relatively cheap and easy to replace.

I have the speedball kit to put in yet but to be honest I’m scared now. Will my heart health be affected by this shock? I kept my left hand in my pocket and wore rubber shoes.
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You took all the right precautions -- so that greatly minimizes the risk of shock. Did you actually get an electrical shock?  You'd feel it in your finger/hand if you did.  If you don't feel comfortable doing the Speedball upgrade, the good people at BH offer repair and assembly for a fee.  I'm sure they could also replace the burn-marked resistor if you wanted.

cheers, Derek
 
Thanks Derek for the great response, and others as well. I have the alligator clips that are they’re own lines. I also have two lines that are just test probes. I just touched the red clip to the terminals after it threw a spark and was easier. I think I can do the speedball. I think the white resistors leads were touching another lead so it threw a spark. Thank you for all the help!
 
That's a very nice job for a first build! Looks good.

I noticed that you've got a bunch of longish lead ends poking around. My personal preference would be to bend the excess leads around the terminal lug, crimp them, and then give the joint a extra shot of solder.  Otherwise they should be trimmed.

The temp display on your soldering station shows "480" -- I assume that's 480 Celsius -- so nearly 900F. That's an impressive soldering temp! But in the off chance that it is 480 F, then it's too low. 480 F is just barely above the melting temp of standard 40/60 solder and is a recipe for cold solder joints.  I wouldn't go lower than about 650.

have you listened to it yet?

cheers, Derek
 
Deke609 said:
That's a very nice job for a first build! Looks good.

I noticed that you've got a bunch of longish lead ends poking around. My personal preference would be to bend the excess leads around the terminal lug, crimp them, and then give the joint a extra shot of solder.  Otherwise they should be trimmed.

The temp display on your soldering station shows "480" -- I assume that's 480 Celsius -- so nearly 900F. That's an impressive soldering temp! But in the off chance that it is 480 F, then it's too low. 480 F is just barely above the melting temp of standard 40/60 solder and is a recipe for cold solder joints.  I wouldn't go lower than about 650.

have you listened to it yet?

cheers, Derek
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Thanks Derek! It is Celsius! I was wondering too because I know someone said 720 at the tip and I was like it only goes to 480. I had it at that temp most of my build but I made quick connections I didn't get many cold joints, they all look pretty good IMO. Now I know though, I appreciate all this help. Thanks I will trim the leads further. I've been listening to it for a few hours so far and it sounds great. I once had a Bottlehead Crack with the Speedball, but I never got to test the original build. If it sounds this good, I can only imagine what it will be like with the speedball. That's why I got it again. I enjoy tinkering around and I remembered this being my favorite amp of all time for how crystal clear and nice it sounded. I can't wait to do another project, but this one set me back a few bucks which is why it took me forever to finally get it. Maybe I could sell this one and do the kit over again and make it even better. That was my plan, but with the sparked capacitor it might hurt the value. I know it's easy to get a new one but that was a difficult adventure getting those in the right place. Do you have any recommendations on something else I can build?
 
For working on the Speedball pcb, you might want to dial that down to 650-750 F for most of it.  With the exception of the large, black rectangular transistors and the heatsink posts, the Speedball bits don't need much heat - the red diodes, in particular, barely need any.

As for the spark causing harm -- the first and best way of testing for that is to redo your resistance and voltage checks.  If they're all good, then I'd bet the amp is too. I don't think brief spark jumping from the high voltage wiring to ground (e.g., from terminal 2 to terminal 3) could possibly do any harm in the Crack.  But if you're concerned about that, you can ask PB, the amp's designer.

As for future projects, I'm sure you can gets lots of varied advice about that from others on the forum. The BH power cord kit is a quick fun project.  Another popular project is building your own interconnects - there are lots of recipes online.  and yeah, building multiple Cracks is also an option. There's at least one active user on the forum who seems to build a new one about every month - presumably for sale. And I'm pretty sure there are a bunch of people around the world who have basement side businesses of making and selling Crack(s).

But if you really want to get into tinkering with the amp, I'd consider selling the current one (or keeping it) and getting the Crackatwoa (which i just this second realized is a play on "Krakatoa", the volcano).  I don't have one, but I have experienced the benefits of a shunt regulator in another BH amp (Stereomour II) and was blown away.  Plus, the Crackatwoa gives you lots more space to add big components like huge film caps.  I'm a big fam of tinkering with my BH amps, and I can say from experience that it's easy to run out of chassis space -- no doubt due to my tendency upon seeing any open space of dimensions X by Y by Z to immediately find a part that is at least 25% too large and attempt to jam it in (usually successfully!).

So lots of options!  Enjoy the Crack!

cheers, Derek
 
Yeah, though your photos don't show a lot, I do see patience and care taken with the build, which pays off in the long run.
 
Deke609 said:
As for future projects, I'm sure you can gets lots of varied advice about that from others on the forum. The BH power cord kit is a quick fun project.  Another popular project is building your own interconnects - there are lots of recipes online.  and yeah, building multiple Cracks is also an option. There's at least one active user on the forum who seems to build a new one about every month - presumably for sale. And I'm pretty sure there are a bunch of people around the world who have basement side businesses of making and selling Crack(s).

But if you really want to get into tinkering with the amp, I'd consider selling the current one (or keeping it) and getting the Crackatwoa (which i just this second realized is a play on "Krakatoa", the volcano).  I don't have one, but I have experienced the benefits of a shunt regulator in another BH amp (Stereomour II) and was blown away.  Plus, the Crackatwoa gives you lots more space to add big components like huge film caps.  I'm a big fam of tinkering with my BH amps, and I can say from experience that it's easy to run out of chassis space -- no doubt due to my tendency upon seeing any open space of dimensions X by Y by Z to immediately find a part that is at least 25% too large and attempt to jam it in (usually successfully!).
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Thank you! Yeah, I am very new to electronic building. I had to learn how to use a multimeter from youtube and looking at photos to see which one was AC, DC and Ohms. I know Ohms pretty well, it's a bit easier I think. Either way, I'd like to complete this one, then sell it and buy another crack and make it perfect this time. I mean I only messed up at that spark and everything else I think I did a pretty darn good job and I don't say that often. The instructions are just so clear and precise that it made it a ton easier/fun not having to figure anything else out myself. It never said to clip the leads, but I looked at the photos and they did too. I've seen some professionally built Cracks and they have theyre wiring so tight and nice I'd like to try something like that too. I only have a set of the HD600 so I'm not sure if the Crackatawa would be a wise investment. I've had a ton of fun with this crack (no pun intended), and I just really like it. I once had a set of Grado SR325i that I paired it with and it blew me away. Things were so clear, but it does very nicely with my HD600 too. Can't wait to see what the speedball does. And from reviews, the power cord even further makes it better. It's such a simple and effective design I tell everyone about it. I'm like yeah, I've tried a bunch of Solid State amps and some other tube amps, but I need the BH crack back!
 
Paul Birkeland said:
Yeah, though your photos don't show a lot, I do see patience and care taken with the build, which pays off in the long run.
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It took me over a week just to spray paint the top plate and stain the wood. I put clear coats on both and made sure it dried, so I was waiting day after day for that. I actually built the amp all day Sunday. I have a little experience wiring stuff up, but not much. The instructions were just so great and I was in a roll. Next time I'm going to make it neater though.
 
You know, if you are concerned about burn marks on the long white resistors, then it's something you don't need to worry about if you add the Speedball upgrade. In making the upgrade you actually remove and discard those resistors!

Another kit I would consider as a second kit would be the Single Ended eXperimenter's (S.E.X.) kit. It's a great headphone amp that can be used with pretty much any headphone, not just the high impedance ones that the Crack plays well with. On top of that, you can add efficient speakers and listen that way. You would be surprised at what a 2 watt amp can do with the right speakers!

Congrats on a nice Crack build! Looks great!
 
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