Jeb's Build

[Grainger49]

Jeb,

The product page lists a number of options to the right.  The top one is the 120V/240V option.  It says:

"The stock kit is designed for 120VAC mains. Select this option to order the kit with a 240VAC power transformer instead at no additional charge "

If you did not select this option you probably got the 120V transformer.  The transformer indicates the incoming voltage at the upper left at the terminals.  What does yours read?

[Jeb Jeb]

Hi Grainger,

yes I selected 240 when ordered and the transformer indeed says 240V PT-3 - so I think I'm all good   Not knowing anything about this I just wondered if it made any difference to the voltage readings using 240V but now I understand that it would make no real difference to the readings between 120v into 120v transformer  vs  240v into a 240v transformer.   Just creating confusion with my limited knowledge   

Jeb

[Grainger49]

You are in good stead.  You will get proper voltages out of the transformer.  You will get them all around the circuit if it is wired properly too.  A lot of Cracks run right off the bat.  What we see on the forum are those that don't.

[adydula]

I am interested to know if the 240 VAC primary side steps down the voltage on the secondary side or not?? Any one that is an expert here have a answer to that???

Alex

[Grainger49]

Transformers change voltage.  The heater winding is transformed down to 6.3V.  The high voltage windings (2) transforms the voltage up to (120V, down to 240V) 150V.  So it depends on what the primary winding is as to whether it goes up or down.

[adydula]

Yup the sure do.... some step up, some step down, some don't at all depending on the requirement.

The heater voltage windings is an obvious step down, while the 170 Volts DC B+ seem to indicate a step up.

Alex

[mcandmar]

Think of it as turns around the core.  If the primary and secondary windings have the same numbers of turns around the core then the input and output voltage will be the same. (i.e. an isolation transformer).   If the secondary has half the number of the turns than the primary it will have half the voltage.  Double the turns, double the voltage and so on.

[adydula]

It looks like the crack transformer has two sets of windings for the plates and one for the filaments? on the secondary side that is...

Alex

[Jeb Jeb]

Hi guys,

just performed the resistance checks. 

1) The only terminal that gave me some varying readings was Terminal 13.  I understand it has a "*" so we can expect some variation here.  Sometimes It would read 230K Ohms and climb up slowly (as stated in the manual) while checking again would reveal a different reading starting at 3 or 400K Ohms and climbing downwards.   Another time it started at 80K and crept up

So some variation is okay but is it okay if I'm getting some different readings on this terminal each time I check?

 
2) The first time I measured the  terminals that should measure 0 ohms I used the 2K setting and got 0 on each terminal.  I wondered if I should have been checking these on the very finest setting so on the multimeter I bumped down to the smallest setting (200 ohms) .  On this setting these terminals read between 00.4 and 00.6 ohms

As suggested earlier I tested to see what the reading was when I clipped the black lead onto the tip of the red probe itself
and it reads around 00.3 to 00.5 ohms on that same finest setting.


At first I thought all this seemed as expected but then doubt got the better of me so thought I would just run this by you guys first before moving on.  During tests Black lead has been clipped directly onto the ground buss wire.

readings/pics are attached!

and..thank you!

Jeb.

[Grainger49]

Your readings look good.  Anything under an Ohm should be considered zero.  You are reading the meter lead and wire resistance when it reads under an Ohm.

Terminal 13 is an odd ball.  It has 3 big capacitors in parallel with a high resistance (470k) to ground.  If there is a slight charge on the capacitors you will not get the exact reading.  It often gives an odd reading.

Go on and move on to the voltage tests.

[adydula]

Ok now for the voltage checks!!

Good Luck!

Alex

[Jeb Jeb]

Grainger, Alex - thanks I've gone ahead and done the voltage checks.  Probably the stage that was most daunting to me!! To me readings seem okay and within the tolerances given but for peace of mind would appreciate a second look.

As with the resistance checks, on the 0 reading terminals, I saw 0 when using the higher 200v setting but when bumping the meter down to the lower setting (2V) I did occasionally see a slightly varying .002-3 fluctuations but I guess this is nothing to worry about?


Jeb.

[Strikkflypilot]

All Your readings are within the 10-15% limits

Your fluctuations are fluctuations of 0 and nothing to worry about

[adydula]

Wow! Jeb how does it sound!???

I just tore mine down to install the speedball mod...

Alex

[Jeb Jeb]

adydula - in a word - Magical!

Guys - it's working like a dream. Using my new 650s it Sounds absolutely wonderful!  I've had the 650s since the beginning of the build but because I had to clear the decks of all other equipment, up to this point I've only been able to test them out a portable dac/amp and I wasn't sure I liked them.  Clearly the little amp was not driving them to anywhere near their potential - The transformation using them out of the Crack is really outstanding!

I'm planning a full review and some comparisons in due course but for now I'd really like to extend my sincere gratitude to the Bottlehead team and everyone here on the forum who has helped me along the way.  Prior to this my experience with electrical was precisely zero and you've all helped me achieve something I wasn't totally sure I would be able to do.  I'm sure that was evident and you've all been extremely patient! It's been an amazing, confidence building exercise.

I've posted a few photos I've taken:

 I wanted to keep the look clean and simple so took Doc's advice and just applied a few coats of a satin-water-based clear varnish to the well-sanded base.  The top plate is left unfinished.  I added some little oak squares to the inside of the case and added M6 threaded inserts so I could screw in some feet.  Along the way I also built a platform for the Crack to sit on, on my desk -  this is made out of a slab of thick birch ply, some aluminium feet with a clear acrylic top.  The aluminium spike shoes are inset flush in holes I cut into the acrylic, so once it's seated the Crack doesn't move at all.  I added a clear, vented base to the bottom of the crack. 

Finally, the bit i'd been most looking forward to - I stuck on the badge


Again, thank you everyone!!!