Build Log: A Physician hooked on Crack (My very first DIY project)

[sanadsaad]

Ok so im starting the build finally. Got a hold of everything to assist in the build after consulting with you guys. Went through the manual a couple of times. Now here's my 1st question. I have bought the Speedball upgrade with the Crack. Should I first build Crack and then upgrade to speedball or would it be better and easier to skip some steps on Crack to put the Speedball upgrade in one build? Plan is to go through a few soldering videos(paceworldwide, other DIYers videos), practice a bit and then start with the Crack. I picked up the Minty boost recharging device and will use it as my first soldering project(I have never soldered before in my life). Tonight i'll assemble the parts as shown in the manual. Im really bad with the screw sizes mentioned in the manual. Placed them side by side and used the parts list to get a good idea of which is which. I will be needing tons of help when I start soldering and then testing voltages. Going through the build threads here has made me a bit scared regarding voltages and damaging my Senns(650). My predicament is that Im in Oman and there arent many components available here. If I blow something up, project ends there. So i'll go step by step and keep this thread updated. Wish me luck!

[Noskipallwd]

Hello,
The Bottlehead folks all recommend building the Crack without the speedball first, this is what I did. This will give you an idea of what speedball does for the sound. This gave me an appreciation of the importance of a constant current source. Also, you make the build just a little longer. I was extremely satisfied when I finished, but I also was disappointed that I had nothing left to build, so much so that I ordered the Eros!

Cheers,
Shawn

[Grainger49]

With no source for parts handy just measure the resistance of each resistor before soldering.  There are not many in Crack, but it will help.

After each solder joint measure from a permanent part to the lead.  Say you soldered a resistor to a terminal.  Measure the resistance from the terminal to the resistor lead.  Do not include the solder joint.   This will help you find any solder joints that might be iffy.

For your meter readings check question 7 in the FAQ Thread.

[Noskipallwd]

If you need reference in identifying screws and other fasteners these might help. http://www.boltdepot.com/Fastener-Information/Printable-Tools/ Just make sure you print to scale. Also, after thinking about it, I would definitely build the Crack stock first. That way if you have to troubleshoot you don't have the speedball to worry about. Also, when you install the speedball you wil have a properly operating amp, which makes troubleshooting the speedball much easier.

Cheers,
Shawn

[sanadsaad]

So I finished the assembly of the board and before I start the wiring, I thought i'd do my first soldering on a smaller project: The Minty Boost kit charger for USB devices. Turns out im not that bad when it comes to soldering but Im really glad I tried on this PCB first. Much of what I read, saw and thought regarding soldering was a bit different from actual hands-on soldering. Although I thought a couple of solder joints looked weird, and some of the solder didnt fill through the hole, the voltage testing went perfectly and The Minty boost worked like a charm. So I think im ready for wiring now. Lets hope the terminal soldering goes well. One question: I saw videos of people tinning the wires before soldering to the terminals. Should I do that?

[Grainger49]

I agree with Tim, you shouldn't need to tin wires.

Good luck!

[sanadsaad]

It says in the manual to go one turn around the safety ground lug. I inserted the wire into the safety ground lug, turned right and kept the wire at the 16L to be soldered. Am I doing it correctly or do I need to do another loop full around the lug?
Another query: When I connect the red and black wires to B8L/B8U and B7L/BLU respectively, do I solder them as one? Does it matter if solder connects both above and below wires in their respective holes in the heater pin?

[Laudanum]

If the manual suggests a full wrap of the ground lug, it's to make sure there is good physical contact of the wire to the lug before soldering.  The same reason why it's suggested to crimp the wires with needle nose pliers to the terminals they will be connected to.   In all actuality, if you have already soldered but made good physical contact with the lug without wrapping,  it will be fine.    

The upper and lower holes of the large tube socket lugs are electically the same.   If I understand what you are asking ... no, you dont have to completely bridge the solder between the lower and upper holes.  The lug itself is a conductor for it's entire length.  Doesnt matter if the solder brigdes both holes together or not.  Just make good contact with the wire to the lugs and then a good solder connection.

Same will apply to the terminal strips upper and lower connections.  Just for an example, T-17U and T17L.  They are electrically the same, connected by the fact that the terminal tab itself is a conductor.  So when a connection is called for both the upper and lower portion of the same terminal number, you dont have to make a solder bridge between the two holes.

Hope that was what you were asking anyway  

[earwaxxer]

Welcome to the first of many equally fruitful addictions!

[sanadsaad]

Yep thanks a lot Laudanum! Man am I addicted. I started soldering hours back and thought "Hey, id start and do two pages and do some more tomorrow." Im left with just 8 pages(an hour max) and im done soldering and onto voltages! Its 5am in the morning. Time just flew by! Im glad I ordered the speedball upgrade with this. More time spent building! Im as high as a kite right now. Part of it might be attributed to the solder fumes ive inhaled

[Lar]

Crack will do that to ya................

[Noskipallwd]

I bought one of the solder fume filter fans some time ago, and it never gets used. Waste of money.

Cheers,
Shawn

[sanadsaad]

Completed soldering. Im seeing a mismatch on the resistance readings. Bad joints probably. Here they are:

Terminal:My reading:Manual reading
1: 22.6: *
5: 22.6: *
7: 0: 2.9
9: 0: 2.9
13: 0.5: * to 270

B3: 0: 2.9
B6: 0: 2.9

RCA
Center: 101.3/101.5: 90K-100K ohms

HELP!!

I think 7 and 9 are cold joints. Im workin on those. I know its probably something basic but im an absolute beginner so im posting my results here as I go along!

[Grainger49]

Pulling out my "custom" schematic with terminal numbers on it...

I have now figured out you haven't been using multipliers.  They are important.

As above for the meter readings and making heads & tails of them refer to the link supplied.

Terminal 1  is the plate of the 12AU7 so with no tube there it is connected to the power supply through the 22k1 resistor.  The capacitors should charge giving a reading that starts in the thousands of ohms and goes up to maximum (that is when the batteries in the meter charge the caps enough to be infinite resistance).

22.6 ohms, not 22.6k ohms says something is wrong.  Check the resistance of the resistor between T4U and T5U, but measure from tube pin 1 and T4.  Check the resistance of the resistor between T2U and T1U but measure between tube pin 6 and T2.  Both should be 22k1 ohms.

Check the 270k ohm resistor between T13U and T12U (page 30, bottom of the page).  Since it is across capacitors it will start at the value of 270k and climb.  

Terminals 7 and 9 are attached to the left and right cathode resistors of the 6080 tube terminal B3 and B6.  Those are the big honkers in the middle of the chassis.  It is unlikely they were shorted (zero ohms that you read) to begin with.  Each should measure about 3k ohms.  Try placing your meter leads on the resistor leads of the left one then the right one.  You should get close to 3k ohms for each.  If you get zero, there is a short somewhere that is shorting out the resistors.  I suspect the resistors are good.

Terminal 13 is the output of the high voltage power supply.  It should charge all three big capacitors.  It should start at about 270k ohms and climb to infinity or near that.  If it is shorted there is a big problem.  

Start looking for this by carefully checking the orientation of the power supply diodes, manual page 27, lots of pictures.  Verify that the banded ends of the diodes are as shown in the picture.

Next verify that the capacitors have the white banded end where they should.  They are all installed on page 30.  The first one has the white band toward the front of the amp, it is pictured from the side.  The second and third (mounted horizontally) also have the white band toward the front.

Your RCA jacks are within 1.5% of expected.  That is as good as it gets.

[sanadsaad]

I did the checks as you asked. Here are the findings:
Tube pin 1 and T4 = 22k ohms
Tube pin 6 and T2 = 1

Terminals 7 and 9, both measurements are 3k ohms.

Terminal 13 is still giving me 0.5k ohms reading. Ive checked and rechecked all orientations and they are according to the manual.

Im trying to upload images onto photobucket and will post any images of specific terminals you may want to see. Im attaching a pic of terminal 13.

EDIT: If it makes any difference, on page 19 of the manual, there's a revision advising attaching a black wire to terminal 4 and soldering to terminal 14U instead of 22 yielding a quieter operation. I soldered to 14U. If that helps in anyway.