voltage problem (and more) in crack -things have gone from bad to worse [solved]

[bobster]

Hi,

I finished the assembly of the crack and all resistances  checked out except 13, which started out at a mega ohm value and slowly decreased.  I double checked connections at 13 and wires resistors coming to 13 and couldn't find anything.

Proceeded to the voltage check.  Although the small tube glowed brightly, the larger tube did not glow at all.  the voltages were all wrong (many were 0).

Turned off, unplugged removed tubes and fuse and re-exained the wiring.  Wire going from 20U to 14U had pulled out of 14U.  Repaired it, rechecked resistances and fired it up for the voltage check.

Small tube lit up again but not the large one.  Started voltage check  began to smell something hot.  The 270 ohm 5W resistor between 13L and 15L began smoking.  Unplugged and found that the solder at 15 U got so hot that it had melted and the wires running into it were loose.  I started poking around and the ceramic cover of the 270 ohm resistor between 13L and 15L crumbled and fell off.  Does this mean the resistor is dead?  Should it be replaced.  Who knows what else was damaged in this process?

Went back and checked the resistances and they all check out.

Now when I plug it in, nothing happens - no tube glow, no voltages anywhere - and yes the fuse is still okay.

Sure could use some suggestions on what to try next.  Should I take it all apart and start all over?

Any and all suggestions welcome.

Thank you in advance

Bob

[vetmed]

IIRC there are 2 power resistors, both of 270 ohms? Anyway, when I built mine I miswired  one of these 2 resistors to ground instead of the positive side of the PS cap resulting in symptoms you have described. Check that both these resistors are connected to the correct terminals. Replace the damaged one with one of similar wattage or higher. If you can get 270 ohms that would be nice but slightly higher or lower would be acceptable; I used two 500 ohm 5 watt in parallel for 250 ohms because that was all they had at the local electronics surplus store

Regards
     Robert Lees

[audiophileboss]

To be honest, this is what you MUST do:

Contact queen and get her to send u a new 270 ohms resistor. DONT TOUCH THE CRACK EVEN ONCE while you wait for it to arrive. Gove yourself time to calm down(i know its hard). Then re install it. Then rewett all of the solder joints on both tubes, and check that they are wired right. Also, check that your leds light up. Then check for any leads that are too long and snip them. If that does not work, and your big 6080 tube does not light up, the tube is blown and request for a new one. But take a week off from working on it. Also, make sure your power rocker is not damaged...it may be that is why nothing lights up

[Paul Joppa]

In a couple cases recently, the 6080 doesn't light up because the socket is rotated 180 degrees. It's way too easy to do that, so check that very carefully if you haven't already.

[Grainger49]

Start with Dan's procedure:

http://www.bottlehead.com/smf/index.php/topic,1667.0.html

When you post resistances or voltages give the expected and your measured.  Only post those that are out of range (+/- 15%).

[bobster]

Thanks for all of the suggestions and help.

Okay - got a new resistor and have been away for a week at the beach.

Installed the new resistor and double-checked all connections.

All resistances are spot on.

Now I am blowing a fuse.

While I am scrutinizing every thing with a magnifying glass, can someone tell me if the 0.5 amp fuse is a slow-blow type and what voltage it should be rated at.  I see a 0.5 amp slow-blow fuse at radio shack rated at 250 volts.  Will this work?

Bob

[Paul Birkeland]

Go ahead and grab 1A slo-blow fuses.

Try powering the Crack up with no tubes installed.

I would be willing to bet one of the 3 black capacitors is in backwards.

-PB

(you can always post photos too, sometimes it can be easy to spot things visually)

[bobster]

Paul - you are a genius!  I was gong to take your bet because I KNEW that they were in correctly - because I had checked them twice when I was installing them and had been back over them again.

Although there were three (count em 3) check marks by the capacitor at U20 and U21, it was in backwards.  Once I fixed that and replaced the fast-acting with a slo-blow 1 amp fuse, all is right in the world.

How does it happen that someone looks at a capacitor orientation three times and misses that it is in backwards - three times?!  I can only imagine after the first time, my mindset was it was okay the first time, how can it be wrong now?  A lesson learned.

Thank you again

[Paul Birkeland]

How does it happen that someone looks at a capacitor orientation three times and misses that it is in backwards - three times?!

I have no idea, but I still make the same mistake after 10+ years.

I'm glad you got the kit up and running, now it's time to sit back an enjoy some tunes!

[bobster]

so I hook this up to my foreplay?

[Grainger49]

Bob,

I have done the same exact thing.  It is embarrassing.  There were two of us, one called out the position of the stripe, the other looked.  Then we swapped places.  We looked it over 4 or 5 times and still got one or two wrong.

I'm going to blame age and eyesight.

[Paul Birkeland]

so I hook this up to my foreplay?

I wouldn't bother, just connect your source to the input of the Crack.  (You wont want/need the extra gain)