Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: denti alligator on January 17, 2015, 09:50:08 AM
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Building my Crack slowly. I'll post the final pic here when I'm done, but I had a couple questions about the manual/build.
One: there are 2 #6 small round lock washers in the kit, but I only see where one was used in the build. Did I miss the other?
Two: on page 13 there appears to be a mix-up of screw lengths being used to secured the two different tube sockets. Just a note for future revisions to the manual. It's pretty clear which screw one is supposed to use.
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One: there are 2 #6 small round lock washers in the kit, but I only see where one was used in the build. Did I miss the other?
Each should go under the #4 nuts that hold down the 9 pin socket.
Two: on page 13 there appears to be a mix-up of screw lengths being used to secured the two different tube sockets. Just a note for future revisions to the manual. It's pretty clear which screw one is supposed to use.
That's not a mistake. If you end up installing the Speedball later, you will wish the long screws in their proper places.
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I've been following the manual very closely and did not see where the second lock washer was mentioned:
Place the nine pin socket retaining ring over the socket and insert a 4-40 x 3/8†screw through the rear mounting hole.
( ) Hold the screw in the hole while you flip the chassis plate over, and slide a five lug terminal strip over the screw, oriented as shown in the photo. Secure with a #4 nut. Slip another #4-40 x 1/4†screw through the front hole. Slip a #6 locknut on the screw from the underside and secure with a #4 nut.
No mention of using a locknut on the first screw.
As to the screw lengths: the language suggests that one is supposed to use the same size screws for each socket:
Octal Socket ( ) Start by putting a #4-40 x 3/8†screw into [...] and insert another #4-40 x 1/4†screw in the rear octal
socket mounting screw hole from the top side.
[...]
Nine Pin Socket
[...] insert a 4-40 x 3/8†screw [...]. Slip another #4-40 x 1/4†screw through the front hole.
So I should use two differently sized screws for each socket?
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It looks like the instruction for the second lockwasher isn't in the instructions. You can use it under the nut to hold the 5 lug strip on the 9 pin socket, that's where it should be.
Each socket gets a 4-40 1/4" screw and a 4-40 3/8" screw, they go in the the locations as instructed in the manual. (You can disregard "another")
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Thanks, PB. I will make these changes before moving on. You might want to change "another" to "a" to avoid confusion in future revisions... Though really, that's a nitpicking correction.
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Everything else seemed to go well enough in the build.
I was wondering why the manual only has one check resistance on some of the terminals, but not all. This is especially odd, because some of the terminals to check have nothing attached to them; yet some that are not listed DO have things attached to them.
Now that I look ahead at the voltage check I see that terminals 18 and 19 are skipped there, too. Any reason?
My resistances were right on, except that terminal 13 appeared to be DROPPING, not climbing. (I just checked this again, and yes, it starts at around 3k and keeps dropping.... I haven't waited to see how far, but definitely below 2.7k.) Is this something to be concerned about?
Also my left RCA measures 87.5k and my right RCA 97.7. Is that something to be concerned about?
Also: the manual says a good place to attach the negative lead of your meter is terminal 12, but there's no ground there). Shouldn't it be terminal 16?
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Voltage isn't right. See above for resistance inconsistencies. Tubes both glow. Only A8 LED lights up. The A3 one does not.
Voltage issus:
T5: 149
T9: 147.3
A1: 148.6
B4: 148.7
B6: 148
All others are within range. What might I have done wrong?
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Do both halves of the 12AU7 glow?
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Do both halves of the 12AU7 glow?
No, it don't think so. Just one. The one closest to the power input/back of plate is glowing; the one closest to headphone jack/front is not.
I just double checked all the wiring. Seems to be correct. I don't see anything unsoldered. I reflowed and added a bit of solder to A3.
That LED still doesn't light up.
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Terminal 12 is grounded via the TRS jack that is in turn attached to the ground lug of the potentiometer which is connected to terminal 3 that is the start of the ground.
Here is the ground path of the Crack as described in one of Grainger's posts:
http://bottlehead.com/smf/index.php?topic=4812.0
Richard
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No, it don't think so. Just one. The one closest to the power input/back of plate is glowing; the one closest to headphone jack/front is not.
That LED won't light up if its half of the 12AU7 isn't glowing. The red wire to A4/5 provides the heater voltage to make this happen, double check that this connection is well made.
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No, it don't think so. Just one. The one closest to the power input/back of plate is glowing; the one closest to headphone jack/front is not.
I just double checked all the wiring. Seems to be correct. I don't see anything unsoldered. I reflowed and added a bit of solder to A3.
That LED still doesn't light up.
Have you checked if the LED's are correct in orientation?
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Have you checked if the LED's are correct in orientation?
They are. I'll double check the wiring in about an hour when I get home. What do the high voltages at T5, T9, A1,
B4, B6 suggest?
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Don't take my word for this but it sounds like some of your resistors aren't bringing the voltages down to the proper levels. You checked the LED's on the 9 pin miniature socket as well right? That was the one that I missed last time when I had the bands wrong which didn't bring the voltages to the right level. Also, check the fast/soft recovery silicon rectifiers (black/silver banded tiny things) and make sure they are positioned properly.
One last thing, make sure no wires are touching any other wires. This could lead to shorts which will cause your Crack not to work properly.
Posting pictures might help us find the cause of your problem.
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I reflowed A5 and A6. Still not working. Any other ideas?
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They are. I'll double check the wiring in about an hour when I get home. What do the high voltages at T5, T9, A1,
B4, B6 suggest?
They are all related to the same problem, that one half of the 12AU7 isn't glowing.
If you believe it to be the LED, you can connect a wire between A3 and A8.
-PB
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If you believe it to be the LED, you can connect a wire between A3 and A8.
I don't know anything ... I'm at your mercy :)
All I know is what I've posted. Is it possible the LED isn't working? is broken? What will wiring A3 to A8 do?
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Wired A3 to A8. Same problem.
What should I try next?
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Wired A3 to A8. Same problem.
What should I try next?
I'm guessing one or both LED's light with the jumper in?
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I'm guessing one or both LED's light with the jumper in?
Hadn't looked at the underside. Only half the tube glows (same half). Both LEDs light up now. Haven't re-checked voltages.
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What should I try next? Should I remove the wire between A3 and A8 to start with, now that we've determined the LED is fine?
EDIT: Just double-checked all the wiring. Unless I'm overlooking something (possible, of course), I think everything is where it should be.
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What are the chances the tube is no good?
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Why don't you measure the resistance across each half of the heater?
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Why don't you measure the resistance across each half of the heater?
Can you tell me how to do this.
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Set your meter to Ohms, put the black probe on pin 9 of the 12AU7 out of the socket, then measure resistance between 9 and 4, then 9 and 5.
-PB
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I reflowed A5 and A6. Still not working. Any other ideas?
Judging by the picture it looks like you didn't put enough solder on some of those terminals but it could just be the way I'm seeing it from the picture. I don't think it would hurt to add extra solder.
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Set your meter to Ohms, put the black probe on pin 9 of the 12AU7 out of the socket, then measure resistance between 9 and 4, then 9 and 5.
-PB
You mean the tube itself? pin 4 is 4.38k; pin 5 is 7.5
(Seems like pin 4 is fluctuating. Now I'm getting in the 600 range. Yeah, every time I try it I get a new number, ranging from 300 to 47k. Meter works fine, as far as I can tell, measuring other things.)
The solder on the terminals is about how much I've used on my past three successful BH builds.
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Does this mean I have a bad tube?
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Could be bad, but try cleaning pin 4 and measuring one more time.
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Used deoxit. Still measuring all over the place.
EDIT: Guitar shop downtown has some Electro-Harmonix 12AU7s. Those any good? I might pick one up to hold me over till a replacement comes if it's really this tube that's bad.
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Yes, the EH will be fine.
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If it works do you guys want to reimburse me for that instead of sending me another one? $15 I think. Or would whatever you send me be better?
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You can try an EH 12AU7, just to rule that out. Also, you mentioned reflowing A5 and A6, it's A4 and A5 that make the tube glow (and A9).
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If you would like a replacement tube we are happy to send one. We are not able to reimburse for the purchase of a tube from somewhere else.
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Yep, it was the tube! Popped in the EH 12AU7 and both LEDs are glowing. I'll go check voltages right now.
And the voltages are now right! So I did the build right to begin with, which makes me feel a little better. I'll contact Eileen for a replacement tube.
P.S. Are the tubes tested before being sent out, and if so does that mean this one was damaged in transit? (Just curious)
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And it sounds lovely!
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Great to hear! Enjoy your Crack my man!