Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: Droo on April 07, 2020, 06:19:41 PM
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Hi,
After receiving my crack with speedball, I first built the stock crack over the course of a day, and have been listening to it for a couple of days now. At this point, all resistances and voltages were correct, so yesterday I decided to do the speedball.
The small board went well, and I was really impressed by how it sounded. When doing the large board, however, two things went wrong: firstly, one of the leads came off of one of the 10W 3K wirewound resistors, so I can no longer revert back; secondly, I somehow lost one of the LEDs on the big board, but being an impatient idiot, I figured the LED was for indication of errors only, and I went ahead with the assembly without it.
When I turned it on to check the resistances and voltages, something near the rear of the chassis started smoking (maybe the transformer), so I immediately shut it off. I didn't know what to do, so I put in a random led I had lying around and mounted it in place of the missing one (with the correct polarity).
When I checked the resistances afterwards, the resistances of 7,9, 10, B3, and B6 all read 1 instead of their proper values. All else is correct. The led was just to complete the circuit, and I have not applied voltage to anything since. I know I have made a lot of stupid mistakes, but I would like some help in figuring out whether or not I made some irreparable damage to anything (especially the transformer) and how to remedy the situation, if at all possible.
Thank you very much for your help.
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I noticed the upper lug of the headphone jack was a little loose, so I resoldered it. 10 is now within acceptable range, but where I was previously getting 00.0 for all 0 values, I now get 00.8 at 200 ohms and 001 at 2000 ohms. I'm worried that this might be too high for safe operation.
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The LEDs are not for indication; the circuit won't work properly without HLMP6000s installed.
The one resistance check in the Speedball manual checks to see if the heatsink mounting kit on the TIP50 is installed properly. The DC resistances on terminals 1, 5, 7, and 9 from the Crack manual no longer apply once you install the Speedball.
What smokes near the rear of the chassis is the 270 ohm resistor closer to the power switch. It will smoke when you don't have the TIP50 heatsink mounting kit installed properly, but since you ran the kit without one LED installed, it's really hard to know what might be damaged on the big PC board.
You can start by setting your meter to check continuity (it will beep when you touch your meter leads together), then look for continuity between any pair of leads on the TIP50 and 2N2222 transistors.
If I had your Crack here for repair, I would pull the LEDs and transistors on that side of the board and throw them away, then measure the R1 and R2 resistances to be sure they were OK, then I would replace the LEDs/transistors on the board.
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Thank you so much! The 270 ohm resistor still seems to work, so I'll just replace the transistors and LEDs and go from there.
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I would recommend testing them...
The only reason I would replace them all if I had the kit here is because I have a pile of each just sitting around, and I'm impatient. If you do not have a spare 2N2222, TIP50, and a pair of LEDs, then you should do a little testing to see which are shorted.
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Hi,
I replaced the LED. All of my LEDs light up and there is no more smoke coming out. After testing the voltages, however, I got the following results: G:0.00 B+:243 OA: 125, OB: 148. These are all DC (1000 V). I also noticed that for some reason the LEDs on the OA side of the board light up as soon as the crack is plugged in, while the rest take a while to gradually glow brighter. How do I proceed from here?
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Sound wise, there's a bit of a buzz in the left channel, and with cymbal hits, there's a very distorted but quiet thump in both rears. Only the left channel plays sound. When I shut the amp off, the distortion temporarily seems to disappear on the left.
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That's a very good indicator that you have a bad solder joint. I would reflow all of the joints in the amp.
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I reflowed everything in the area, which didn't seem to change too much. When I unplugged the left Jack, there was still quiet music going through the left channel. (The right was even quieter, with mostly just some crackling corresponding to bass.
http://imgur.com/gallery/HD4PwgC
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There are a LOT of wires with excess ends that need trimming back. The preference is to make a mechanical joint by crimping the wire around the tag, trimming off and then soldering. Small long nose pliers help here. B2/B3 touching? I prefer to solder components on both sides of a board to make sure the joint is sound. Electrically this may or may not matter but it helps to reduce the chance of colder solder joints.
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Proper side cutters will help to trim those leads back.
Can you take a photo of the headphone jack wiring with more light on the jack?
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I trimmed the leads and reflowed everything from the top to no avail.
Jack https://imgur.com/a/mgTTIa6
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Can you post your voltages?
None of the solder joints on that jack look promising. The middle joint on the outside where the 2.49K resistor connects looks to be unsoldered. The junction of the black wires doesn't have enough solder, the joint with the white wire hasn't been heated enough, the joint with the red wire has the lead of its 2.49K resistor just poking out and hanging out in the air (bend it around the terminal and crimp).
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B+: 248
OA:131
OB:233
G:0.
I think I may have shorted something when soldering the OB TIP50 (with everything off). I may have touched a lead of the big resistor, as I saw a spark and now the LEDs don't light up on this side anymore.
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Just went through everything and confirmed that all capacitors and resistors are good except for one of the TIP50. I'll try to find a replacement and see how it goes. Can I just use any generic TIP50 from digikey?
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Can you give me all of your voltages on all of your boards?
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OB:82
1B:278
BAB:0
OA:89
1A:278
This is with the big board removed.
The big board voltages are on the previous page.
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I suspect you either have a very poorly soldered TIP50, or a toasted transistor.
Bad transistors will show very low DC resistance between pairs of pins, so they are easy to check with your meter.
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Yes, I found that one is fried. Where would you recommend going to replace it?
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Mouser usually has them all in stock.
-PB
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I replaced the transistor, but the LEDs on the same side of the board still won't light up.
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You can use your meter's diode check function to check the LEDs as well.
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Good call, I swapped out the LEDs and now they light. The right channel still turns on first though (immediately after plugging in). I get
250 on B, 130 on OA, 150 on OB and 0 on G.
Oddly enough, I get 0.6 ohms across both resistors in the headphone jack. Might that have something to do with it?
I've tested all the other circuit elements, and everything else seems to be working properly.
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There's either a miswire from the board to the circuit, or there's still a toasted part in your kit.
The resistors on the headphone jack will read 0 ohms with nothing plugged into the jack; that's normal.
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I'm almost absolutely positive that there's no midwife. How do I proceed from here?
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*miswire lol.
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Post some photos of the top and bottom sides of the PC board, as well as the build as it sits now.
Also check the resistance of the R1 resistors on the big C4S board. You can measure their values in circuit.
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All joints https://imgur.com/a/tEgLPw1.
R1 resistances are both 32 ohms, and the resistances of every single other resistor is within 10% of what it should be (except the ones in the headphone jack). Base to collector and base to emitter are between 655 and 740 on every single transistor, probing the joints from the underside of the circuit boards. Diodes are all around 500-600 on the transformer.
All 5 capacitors charge (20KOhm setting used to check). RCA resistances are 92 and 99 KOhms (L and R respectively). Tubes glow on both sides, and neither of them seem particularly bright or hot.
I know one of the TIP50 transistors looks a bit janky and seems like it has a poor mechanical connection, but the leads won't fit in the cutouts, and the resistances from the bottom seem about right. How likely is it that the tubes or the transformer have gone bad? Thanks again for your patience.
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Droo -
If that were my amp I'd do three things before trying to troubleshoot any resistance or voltage issues:
(1) Reflow every solder joint in the amp by (a) placing the soldering tip so it makes good contact with both the lead and the terminal (i.e., both surfaces to be soldered), and then (b) waiting until the solder suddenly flows like water around, and gets sucked into, the joint. From your pics there look to be a fair number of sketchy joints - too many to circle or list. Even if they're working now, I'd be concerned that they'd fail in the future after repeated heating and cooling from use. PB has said he can reflow a Crack in 30-45 mins. So I figure an ordinary human can do it in under 2 hours. Even if this doesn't solve your issue, it will help ensure that the amp, once you get it working, stays working for a long time.
(2) Fix the diodes. You've got all 4 on the same side of the terminal strip. That's a short waiting to happen - either by the leads of two diode making contact or a diode grounding out to the chassis. I'd reinstall them as per the manual or at least insulate them from each other and the chassis (but the latter fix will take more time that simply reinstalling them two-a-side.)
(3) Fix the small 270K resistor in the power supply near the big white 5W 270R resistor. This also looks a short to chassis waiting to happen.
I figure you could do all of the above in less than 3 hours. And who knows, maybe that will solve your problem. And if not, it will make tracking it down a whole lot easier.
cheers and good luck, Derek
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Most of your work looks good to me. Derek mentions fixing the diodes. I wouldn't necessarily do that. Unsoldering them will be very difficult and putting two back in on the other side will be even more difficult. You could slip some electrical tape between them for a minimal level of protection.
Many of your wires still need clipping with a good sidecutter. Those are about $20 with shipping and tax. It's going to be difficult to get to some of the wire ends with everything assembled. You would have been better off clipping them sooner.
I'm with PaulB when he suspects another toasted part. Tubes and transformer are almost certainly still good. They are robust.
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Thank you both so much for the suggestions! I'll definitely try to get better/smoother joints all around and clip whatever leads are still too long. Resoldering the diodes might be a little difficult, but I'll give it a shot, otherwise I'll go with some electrical tape. I want to note that the ones that should not be in contact look like they're in the same plane, but are in fact bent away from each other.
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Yeah, if I got your Crack in as a repair, I would toss that big PC board and completely replace it.
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What's wrong with the board itself? At this point I'm very confused, because it doesn't seem like anything on it is broken, but yet it doesn't work. Should I buy a new speedball?
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When all the LEDs light up brightly before anything has warmed up in the circuit, the board is not working properly.
You can contact replacementparts(at)bottlehead(dot)com about getting a new big board and associated parts. You do absolutely need a proper pair of side cutters to trim things down in there too.
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It works now, and it sounds great!! However, I'm getting 145 on OA/OB and 250 on B+. Is that a problem? It's dead silent when nothing's playing. I'm using the Raytheon 6080 that came with it if that matters. Thanks!
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What are all the voltages on the small PC board? You should not have 250V of B+.
Can you also inspect the solder joint on the headphone jack where the black wires meet? Sometimes one is loose there and that will make your DC voltages look a little weird.
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The headphone jack joints all look solid. One of the LEDs on the B+ side isn't turning on, but the one after it is. I remeasured the big board voltages, and they're actually OA: 116 OB:125 and B+:215. Little board voltages: OA:84, 1A:215 B/AB:0V 1B: 220 OB:79.
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One LED out on the big board is definitely an issue. Your small board voltages look good. B+ on the big board and IA/IB on the small board are all wired together. You can't have different voltages on these board pads without flaky solder joints at work.
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Yeah, I think it went out when I tried to get a better joint on the TIP50. I replaced it and am back up to 235 on B+ and 130 apiece on OB/AB. A weird thing I noticed is that if I tap the input tube, I hear it much more distinctly in the left channel.
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What's your AC wall voltage?
I strongly suspect your big Speedball board is still not working at all. The high voltages on OA/OB indicate that the 6080 is drawing nearly no current.
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It's around 122 V
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Yeah, the big Speedball board is not pulling the proper current. I would suggest a lot more heat on the TIP50 terminals and even the 2N2222 terminals.
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So I reflowed all the joints. I'm now getting 203 on B+ and 110/113 on OB and OA. Is this good enough for operation?
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Yes, that is now a working amplifier.
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Awesome. Thank you so, so much!