Bottlehead Kits > Crack

I swear baby, this has never happened before (please help me, Crack won't work)

(1/8) > >>

Todd R:
The Crack is my 7th  (or 8th if you count the Paramount as 2) Bottlehead kit.
Everyone of them has worked right out the gate except this one.

I hear music faintly in only the left channel if I turn it up all the way. Basically no sound.

I will list only the resistance & voltage checks that differ significantly from the manual.

Resistance, terminal with meter set to the 200K scale:
1 - 22.6
2 - .5
4 - .5
13 - .5 steady

Voltage. Little confused here because it says clip it to terminal 12, but then it says reconnect to ground buss. Which is it?
I used terminal 12 and got basically 0 volts everywhere except...
19- 76.9
21 - 206
A1 - nothing, no wire is connected there.

Will go back & try again using ground buss this time for voltage readings, but for now does anyone have a clue where to start looking?
TR

Dr. Toobz:
The manual has 2 errors I can see: there is a wire that should go to A1 that is going to A2 in the instructions, and the resistor going from the output of the rectifier bridge should go to pin 21, not 22 as in the manual. I caught the A1 error, but not the power supply one, until I got no voltage and realized (when looking at the schematic) that the manual had the resistor going to 22, which is chassis ground.

Interestingly, the Crack is about the 7th BH thing I've built (if you include CCS boards, upgraded irons and 4 amps) and is the first time I've ever had something not fire up right away on the first try. I pride myself on meticulous build skills, so it's a real letdown when it happens! The first clue for me was that the cathode LED's weren't lit, even though the heaters were. Then, I got a nice spark from the first power supply cap, which then made me realize that it wasn't being bled and therefore, the problem was just after that. All resistances checked out normal, though, so you may have a slightly different issue. Make sure to check all of the usual suspects, such as component polarity, unsoldered joints, shorts, etc. It's easy, even for an old-timer, to overlook the obvious.

Todd R:
Dr.
The wire going to A2 instead of A1 makes sense to me. As for the resistor that's going to 22 instead of 21, shouldn't the black wire from terminal 4 of the transformer move to 21 also?

Doc B.:
Guys, I will have to sort the typos in the manual when I get back in the office tomorrow. The photos are of a working prototype, so you can be confident that the way that it is wired in the photos will work.

Grainger49:

--- Quote from: Dr. Toobz on April 25, 2010, 01:17:24 PM ---   .  .  .  
The manual has 2 errors I can see: there is a wire that should go to A1 that is going to A2 in the instructions, and the resistor going from the output of the rectifier bridge should go to pin 21, not 22 as in the manual. I caught the A1 error, but not the power supply one, until I got no voltage and realized (when looking at the schematic) that the manual had the resistor going to 22, which is chassis ground.
--- End quote ---

My emphasis in the above quote.  Shorting the B+ to ground or common is a bad thing.  I suppose that this didn't blow the fuse.  But it will yield pretty high current.  

Do check the resistance of the power supply resistors while making the wiring change.

Navigation

[0] Message Index

[#] Next page