Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: manicmidget on May 28, 2021, 01:08:08 PM
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Hi, I just purchased a broken Crack w/ Speedball to repair it myself, and the seller didn't have the manual as he had purchased it pre-built. It's also unclear which version(s) the Crack and Speedball are. Hoping someone from Bottlehead can contact me to help. Thanks very much!
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Can you post some photos of what you got?
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Thanks for replying! Please let me know if you need more photos.
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That's a Crack 1.1.
On the 5 lug strip mounted by the 9 pin socket, the outer pair of terminals should measure around 75V DC with the amp running, the inner pair of terminals should be around 175V DC with the amp running, and the middle terminal sits at 0V.
On the 5 lug strip mounted to the octal socket, the outer terminals should be 0V, the inner pair of terminals will be roughly 100V, and the middle terminal 0V.
This is about all of the information that you would get out of the manuals. You're also missing the fuse holder, but the fuse looks to be installed at least.
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Thanks very much, that's good to know.
However, I'd still like a copy of the manual if possible -- I'm fairly new to the hobby but I'm already hooked on mods & DIY and I'm trying to learn how the circuitry works and such. Is there someone I could ask?
(And is there some way I can get a replacement fuse holder?)
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You can contact replacementparts(at)bottlehead(dot)com about purchasing a replacement manual and a new fuse holder.
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Thanks very much!
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Did you get this amp sorted out? Looking at the pics I'm not seeing solder on the resistors on the speedball circuit boards. If I were you I'd re-solder ever joint on the amp.
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On the 5 lug strip mounted by the 9 pin socket, the outer pair of terminals should measure around 75V DC with the amp running, the inner pair of terminals should be around 175V DC with the amp running, and the middle terminal sits at 0V.
On the 5 lug strip mounted to the octal socket, the outer terminals should be 0V, the inner pair of terminals will be roughly 100V, and the middle terminal 0V.
Hi, I realize it's been almost exactly 1.5 years since I posted this -- life seriously got in the way.
I did the readings, and the 9-pin socket lug strip is actually quite wonky -- I'm getting ~0V on the outer pair, one of the inner pair reads ~110V and the other ~0V, and there's nothing soldered to the centre pin.
For the 8-pin socket lug strip, I'm sort of getting the values you learned for the 9-pin, i.e., ~75V outer pair, ~195V inner pair, and ~0V centre pin.
(I'm assuming the volume potentiometer doesn't matter here, but it was at the lowest position.)
I'd really appreciate any (more) help you could provide. Thanks in advance!
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Can you post a photo of the underside of your amp?
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Thanks for the super quick reply! I tried to do my best with camera angles. Please let me know if you need more photos.
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Did you get this amp sorted out? Looking at the pics I'm not seeing solder on the resistors on the speedball circuit boards. If I were you I'd re-solder ever joint on the amp.
Hi, sorry for taking so incredibly long to respond. The resistors are indeed soldered, just on the underside.
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one of the inner pair reads ~110V and the other ~0V, and there's nothing soldered to the centre pin.
The inner terminals on the 5 lug terminal strip are attached with a piece of wire. They can't have different voltage readings between the two like that unless that piece of wire is broken or poorly soldered.
I see a lot of untrimmed leads on the C4S boards.
It's incredibly common with weird issues like this to find that one of the black wires going to the headphone jack isn't captured by solder.
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First off, I'm sure you already know, but it looks like I got the sockets mixed up.
There's a wire between the inner pair for the 9-pin lug strip, but not for the 8-pin (the one with the mismatched voltage) -- see photos. I assume they should both have their inner pair connected?
Continued thanks!
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Is it possible the tube is burned out?
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With the amp flipped over and the 9 pin socket closest to you, those front terminals are numbered 1-5, then the terminal strip behind it is numbered 6-10.
Can you provide DC voltages for terminals 1-10?
The 6080 is most likely OK.
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Rounded to the nearest 1V:
1 - 79V
2 - 193V
3 - 0V
4 - 193V
5 - 76V
6 - 0V
7 - 111V
8 - 0V
9 - 0V
10 - 0V
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There's a pretty messy bit of soldering on terminal 9 in your photos, and that certainly won't help.
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Yeah, unfortunately I bought this used/pre-assembled so the solder work is not as nice as I'd like. I'll resolder that joint and get back to you, thanks again. (I'm still hoping I don't have to redo everything...)
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It wasn't the solder joint! Perhaps one of the components it's connected to is burned out?
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The PC board with the heatsinks is symmetrical, so you can try rotating it 180 degrees. If the 0V terminal moves to terminal 7, then there's an issue on the board. If that 0V stays put, something else is amiss.
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What's the easiest way to rotate, i.e., which joints should I desolder?
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You can just remove the wires on the "O" terminals and leave the black and red wires in place, then rotate the board 180 degrees and reconnect the "O" wires.
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Voltages stayed the same.
Could it be the capacitor? No visual bulging or leaking though.
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You could try a different 6080 if you like just as a point of reference. Still, I would expect a bad solder joint or broken wire to be the most likely culprit for your issue.
A cap shorting things down like that would get hot, the top would swell, then it would explode. If this hasn't happened, I wouldn't worry about the cap.
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Okay, good to know. Do you have any suggestions on any particular wires or circuit subsections to start with? Or should I just work outwards and keep testing?
I did take a chance and try the amp with my headphones, and the left side doesn't work. (Swapped L/R and right side didn't work.)
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No, please don't try to use an amp that doesn't pass its voltage checks. Failing the voltage checks means that the amp isn't working and could damage your headphones and we certainly could have told you that one channel isn't going to work with 0V DC on terminal 7.
If you have a really inexpensive pair of headphones that you can use for testing, you can poke around the circuit with a wooden chopstick and music playing to see if there's a spot where poking restores operation of the missing channel, but definitely only do this with the least expensive pair of headphones possible.
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Not to worry, I did use my testing pair of headphones that were free from an airliner. I'll try your suggestion with the chopstick, then if all else fails I'll re-solder every connection and report back.
Thanks so much!
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Quick sanity check. Aren't both sides of the tube supposed to be glowing? I would assume so given symmetry, but the ring on top of only the non-glowing side gives me pause.
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On a 6080, I would look at the bottom of the internal structure to see if both halves are glowing. If you're absolutely sure that one side of the 6080 isn't lighting up, then that would point to a defective tube.
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Yep, I am absolutely sure it's not. Might not be visible in the photos but I've checked from every angle.
Just in case the tube was damaged somehow by bad assembly, could you please let me know what each pin on the octal socket should be connected to?
Thanks so much for all your help!
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I would just replace that 6080 and see where that lands you.
That issue can't be caused by build issues, as the glowing heaters in both sides of the tube connect to the same pins, and it looks like one of those heaters has become disconnected.
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Gotcha, I'll report back once I get a new tube. Thanks again!