New Crack build and some ideas for those considering one...

musiciseverything · 6474

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Offline musiciseverything

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First, let me say thanks to the forum and the excellent instructions that come with the kit.  Much to my amazement the Crack actually worked after I finished building it.  I am not good with building things but I was careful and slow and triple-checked everything.  It sounds wonderful-black quiet background, wonderful bass and midrange and highs that are sweet and delicate without being at all harsh.  All for $200.

Now, I did discover some little things that may help other newbies.  First, take your time and only work for an hour or two at a time.  Plan ahead and read the directions several times and run through your mind where things go.  Next, give your solder iron plenty of time to get hot.  It took mine about 15 minutes because it was cheap.  Also, the small tube in front barely glows so I was freaked out when I couldn't see the glow.  But i turned out the lights and could see it but it is faint.  Get yourself a good digital readout meter.  It has many uses and is worth the money so you can be accurate.  The specs on resistance and voltage readouts are quite variable, as it says in the manual.  If your readings are in the ballpark , don't worry about it.  I melted one of the terminals on the switch even though I was warned in the manual.  It is easy to do even with a 40 Watt solder iron.  I used a magnifer with a ring flourescent lamp and it was invaluable.  I didn't need alligator clips on the meter since the negative probe fit right into #11 tab.  Radio Shack has 2% Silver solder and it was cheap and easy to use.  I also used a "third hand" base with alligator clips and a magnifier-nice but not essential. 

I would encourage anyone with an interest to try this kit.  Believe me, if I can build it, you can build it.  You will be rewarded with an excellent headphone amp- on par with my $700 ASL tubed amp.  Enjoy!

Offline Grainger49

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Good advice to the new builder.  Most especially the advice about taking your time and reading the instructions several times.  

I would warn anyone new to soldering not to use silver bearing solder as it takes more heat to melt than 60/40.  That would be the reason you melted the switch.  It just takes a long time to melt silver solder and time means you are putting a lot of heat into the joint.  This would be especially bad on the transistors or LEDs that Bottlehead uses in the kits.

But after you have built two or three kits silver solder is nice.  You are used to soldering and will work quicker with enough experience.  For every day work I use Cardas eutetic solder.  I have used thick 4% silver solder but I have a nice Weller soldering station and have been kit building for several decades.
« Last Edit: May 15, 2011, 10:15:13 AM by Grainger49 »

Offline Laudanum

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I use Kester 44 63/37 for most things.  I think it's just a hair tougher to work with than 60/40 and probably a step closer to a good 2% silver than the 60/40.  I have no problems with the 2% silver either.  Kester or Multicore, I have both.  Ive been solderng and kit building for a good while eventhough Im not very tech savvy regarding circuits.  But I think that the 60/40 advice is excellent for anyone new to soldering.

Desmond G.

Offline tubeglow

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As I get closer to the end I haven't ran into too many difficulties. There have been a couple of places where it was a very tight squeeze with the soldering iron tip and 14U on one of the terminal strips is full to capacity with wires and a capacitor lug. I had to move the wires around to get the capacitor to fit but it seems to have worked. Hopefully I'm going to finish it today so I can finally try it out if everything works as it's supposed to. I always get nervous when I apply that first jolt of electricity.

Offline Doc B.

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63/37 is the eutectic blend and it should, in theory, melt more easily and probably flow better than 60/40.

Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.

Offline Billyk

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I prefer the 63/37 blend.
The definition of eutectic:  The proportion of constituents in an alloy or other mixture that yields the lowest possible complete melting point. In all other proportions, the mixture will not have a uniform melting point; some of the mixture will remain solid and some liquid. At the eutectic, the solidus and liquidus temperatures are the same.

Which I take to mean that I can make fewer "cold" joints!!

Don't let the glasses fool ya, Stand beside me when you measure my size. Don't let false estimations overrule you, soon even you might come to realize. I've been a wizard since my childhood....

Offline Laudanum

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My mistake ... I was comparing with a smaller diameter solder rather than apples to apples, so sorry if I mislead anyone.  I have a small tube of 60/40 that flows a hair easier but it definitely is a smaller diameter than my '44' which is .031.   Anyway, must be the reason why I like the Kester then :-).   I have another roll put away that I picked up years ago when the talk/rumors of trying to get rid of lead based solder was a hot topic.  I'll probably never do enough soldering to ever get to that second roll but I didnt want to ever have to deal with the Cu based solder.


« Last Edit: May 16, 2011, 04:48:47 AM by Laudanum »

Desmond G.

Offline Levent

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I might add this if you are going to add speedball (I built two of these and building the second one was much easier):

1. Pay attention to the wire routing around the back nut (remember that it is a 3/8" screw not 1/4") of nine-pin socket and terminal #3.  There will be a nylon standoff installed on top of that screw over the nut, so don't cover it with wires.  See page 23 picture, if those wires are tight it becomes hard to install the standoff. Leave some slack for the ground wire from the pot to phone jack, see pic at the bottom of page 22.  On my second build I routed that from front of the nine-pin socket.

2. Pay attention to the wire routing around the front nut (remember that it is a 3/8" screw not 1/4") of octal socket and terminal #8.  There will be a nylon standoff installed on top of that screw over the nut, so don't cover it with wires.

3. Don't bend the leads of 22.1K resistors as shown in page 25, leave them slightly bent for easier removal later on.

4. Don't bend the leads of 3K wire-wound resistors (page 32), leave them straight for easier removal later on.  You probably have to cut them off anyway since they are a tight fit.

Also get yourself some solder wick to clean up the solder from those terminals where you will be removing the resistors and adding more wires.

I like 63/37 is better because it is eutectic.  There is less of chance to get cold solder joints - reason below.

From wikipedia: A eutectic alloy solidifies at a single, sharp temperature.  When a non-eutectic alloy solidifies, its components solidify at different temperatures, exhibiting a plastic melting range.