I Need Help With My Crack Problem

[skippy1416]

Hello,

I have completed my Crack build and I am having issues.  All resistance checks are good but when I put the fuse in and turn on the power it results in a blown fuse (I have tried both a .5A and a 1A fuse).  I have rechecked all wiring and capacitor/LED orientation and everything looks good.  I was hoping that I had one of the transformers with the backwards sticker but that looks correct as well.  Since my resistance checks are good I'm not really sure where to start looking to try and narrow down the issue.  I'm not the most experienced builder but I have completed a Foreplay and a Seduction without issue.  Can anyone give me any ideas on how I can go about isolating my issue?

Thanks

[Doc B.]

Is this a 240V Crack? I believe it was just a couple of 240V kits that had the transformers labeled backwards. The easy way to tell if it is labeled correctly is the wires coming out of the coil and wrapping around terminals 4 and 5 are much bigger than those on the the other terminals.

Take a look at the following:
Are the silver banded ends of the UF4007 rectifiers by the transformer oriented correctly?
Are the striped sides of the filter capacitors oriented correctly?

[skippy1416]

Thanks for the reply.

I hadn't realized that it was 240V transformers that had the labeling issue - it was something I saw in the forum that I hoped might provide an explanation.  Everything looks fine with my transformer.

I have checked the alignment of the capacitors, rectifiers and LEDs a couple of times and they look good.  There is also good separation between components and exposed wire ends.  If I get some time in the next couple of days I am planning on cooking the solder joints - maybe that will help.

[Paul Joppa]

That recent thread with the mis-marked transformer (I can't find it right now) had a process for disconnecting the power supplies and gradually reconnecting them, which is a way to troubleshoot a fuse-blowing situation.

[berniebanks]

Here's the link to the post that Paul was talking about

http://www.bottlehead.com/smf/index.php/topic,2453.msg19540.html#msg19540

[skippy1416]

That recent thread with the mis-marked transformer (I can't find it right now) had a process for disconnecting the power supplies and gradually reconnecting them, which is a way to troubleshoot a fuse-blowing situation.

Thanks Paul.  When I disconnected the red wire at terminal 9 of the transformer and retried the fuse didn't blow and the tubes lit up (oddly the red LEDs on the 12AU7 seemed to stay dark but the tube is lit).  I see that this means that the problem is with the high voltage section.  What might my next step be?

[skippy1416]

Here is a picture of what I assume will be the trouble spot (I'm hoping that the attachment works).

[HiFi Builder Guy]

It looks like you have all your rectifiers shifted one position toward the front of the t-strip (the front-most connections are connected to T17, these should be at T18).

Shawn

[skippy1416]

It looks like you have all your rectifiers shifted one position toward the front of the t-strip (the front-most connections are connected to T17, these should be at T18).

Shawn

Hi Shawn,

It would appear that you are correct.  I was so concerned about checking the orientation that I never even noticed this.  I am just about to put things in their proper place.  I will post my results.

Thanks,

Scott

[HiFi Builder Guy]

On second glance it also appears that the red wire connected to 19L is not connected to the Power Transformer (PT9).  

[skippy1416]

On second glance it also appears that the red wire connected to 19L is not connected to the Power Transformer (PT9).  

That was for the check to start to determine the source of the issue.

Well moving the rectifiers wasn't a pleasant job - it would have been much easier to have just done it correctly in the first place.  It seems that I have had success.  The tubes light up (and the red LEDs).  It is getting late here in the east so voltage checks will have to wait (probably until the weekend unfortunately). 

Thanks to everyone to contributed for the assistance.  It is much appreciated.