Crack kit...input power problem..

[es347]

I have assembled the Crack kit and all resistance readings check out but no power to the transformer for some reason.  I have wired the input power from the IEC connector and  power switch exactly as shown in the instructions but no power to the input to the transformer.  It's as if the terminals on the back of the IEC connector are mismarked.  What on earth am I doing wrong?  BTW I am a EE so this is most embarrassing....   HELP please...thanks.

Why is it there is no contact phone number listed for Bottlehead?

[Doc B.]

Since the markings on the IEC connector are molded in it's hard to imagine how they could be in the wrong place. Have you used your meter to trace where the voltage can be found and where it is missing? Is it present at the IEC terminals? Is the fuse installed? Is voltage present at the power switch?

I guess you may have missed the contact number listed at the back of the manual and on our contact web page. It is 206-451-4275.

[es347]

...pardon me while I wipe a little egg off my face.  The fuse was blown.  Weird however because all the resistances checked out but don't recall any checks on the input power wiring.  Any thoughts appreciated.

[Paul Birkeland]

Any thoughts appreciated.

Backwards 220uF caps cause this probably 75% of the time.
Backwards UF4007's cause this maybe 20% of the time.
Metal pieces of components touching where they shouldn't be (a short) is about the other 5%.

[es347]

I went with a time delay GDC 1A fuse and it held.  I must have been charging the caps or dealing with xfmr inrush,etc.  Anyway I got things powered up and the large tube glowed but the little guy, the 12AU7 did not.  Inspection revealed a nice blackened spot on the glass above pins A7 and A8..for reference sake.  Naively I would have assumed if the resistance checks were all good that would indicate no wiring errors.  Would it be possible that the tube was bad?  Sorry but I've retained very little knowledge regarding tubes from my 1966 freshman EE lab so any direction would be much appreciated.  Thanks in advance..

[es347]

Since the markings on the IEC connector are molded in it's hard to imagine how they could be in the wrong place. Have you used your meter to trace where the voltage can be found and where it is missing? Is it present at the IEC terminals? Is the fuse installed? Is voltage present at the power switch?

I guess you may have missed the contact number listed at the back of the manual and on our contact web page. It is 206-451-4275.

Thanks for the phone number Doc!

[es347]

..one last thing...I have a 12AX7 that came with a Fender amp I own...it was loose in the bottom of the case and all sockets were full..weird.  Anyway I was wondering if I should stick it in my crack (no comments please) and see if indeed the 12AU7 that came with the kit was bad.  I know the AX7 has a higher gain but have heard they are essentially interchangeable.  Any problem using it just to see if the AU7 was faulty?  Thanks again..

[Grainger49]

Well, thanks for that visual!

The 12AX7 and 12AU7 are not the same gain. So they are not replacements for one another. But I think it will work.  Not well, but it should work.

I have done worse, but don't brag about it.

[es347]

Grainger...thanks.  Pictures are worth thousands of words or so they say.  I don't intend to operate the amp with the AX7.  Installing just to see if I smoke it too.  I did find an unsoldered joint (could be due to the smoked joint ) on the PS terminal strip but not sure that was the culprit.  Ok smoke test coming up...wish me luck..

[Paul Birkeland]

I went with a time delay GDC 1A fuse and it held.  I must have been charging the caps or dealing with xfmr inrush,etc.  Anyway I got things powered up and the large tube glowed but the little guy, the 12AU7 did not. 

The twisted pair of wires going from B7/B8 to A4/5,A9 makes the 12AU7 glow, check that!

DO NOT put a 12AX7 into your Crack.

[es347]

Turns out the 12AU7 seems to be ok...slight glowing at its top.  Problem:  checked the dc voltages and ALL are fractional...less than 1 volt and negative.  I rechecked all my wiring and found no mistakes.  I am close to relegating this amp to a seldom opened drawer in my shop and sticking with my HH-1...grrrrr. 

[es347]

Well fellas I'm hanging it up.  I can't even confirm the 170V output on the bridge cct. let alone all the other downstream Vs.  This isn't my first rodeo having built Dynaco and Halfer amps back in the dark ages with out a hitch but I must admit this one has officially kicked my ass.  Adios...and thanks for at least reading my posts..

[Paul Birkeland]

If you are able to determine that you don't have the correct voltages, then please do post a voltage list.  If you can't confirm 170V-DC in the power supply, that means that you are reading some sort of voltage there? (Even if it's zero)

[Doc B.]

Have you reflowed all of your solder joints?

[es347]

Doc...I inspected all the joints and they are good.  Regarding the 170V B+ voltage, let me recheck it and I'll post the results..