Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: hardisondan on October 28, 2019, 05:14:37 PM
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Hello,
I'm back after a long hiatus. I looked up my last post and it was 2014. That was when I finished my Crack. After some newbie challenges, I got there and I was really happy with it. It sounded great, and I was constantly amazed at how dead quiet it was, even with volume turned way up there was no background hum or noise of any kind. I PROBABLY SHOULD HAVE LEFT IT ALONE.
Anyway, I attempted the speedball upgrade and it was a big fail. Main tube glows, but no sound. No LEDs on near the small tube. It has been in mothballs for the last five years.
Now I am ready to tackle it again. I have a shiny new soldering station and a new can-do attitude. I am going to re-do the tests to try and narrow it down. I have three questions:
- Firstly, if you had to bet on it, what would be the number one thing people stuff up when adding the speedball?
- Do the resistance check measurements in the Crack assembly manual apply post-speedball? I don't think there was a resistance check list in the speedball assembly manual (but I could be wrong)
- I just noticed on re-reading the Crack manual, that the section on voltage checks mentions they were taken at 110V AC. I am in Australia, so 240V. Does this have any bearing on expected voltage test results?
You might be hearing from me more.
Dan
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- Firstly, if you had to bet on it, what would be the number one thing people stuff up when adding the speedball?
Which Speedball do you have? We made some revisions and the new version has one small, narrow PC board up front and a big board in the middle of the amp, while the old Speedball has two square boards up front. The very long list of mistakes people made with the early Speedballs precipitated nearly all of the changes we made with the second iteration, so this is an important piece of information.
- Do the resistance check measurements in the Crack assembly manual apply post-speedball? I don't think there was a resistance check list in the speedball assembly manual (but I could be wrong)
The voltage checks are absolutely critical. There isn't a useful recommendation that will come about repairing your amp until you post the voltages on terminals 1-10.
- I just noticed on re-reading the Crack manual, that the section on voltage checks mentions they were taken at 110V AC. I am in Australia, so 240V. Does this have any bearing on expected
voltage test results?
The version 1.0 of the Crack had a 120V or 240V power transformer. If you wired up the 120V power transformer to 240V mains, many other things would've failed immediately with your build, so we don't have to worry about that.
You might be hearing from me more.
I hope so, another thing you could do is to post some photos of your build. Some things are pretty easily spotted immediately.
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PBs suggestions are right on. The only thing I would add is to do a few things before you turn the amp back on and check voltages -
With this much time away from the amp what I would suggest first is going through the Speedball manual again and checking that each step was done correctly. Time away from a project like this can actually help you to spot something you might not have seen when you had just finished the build and were troubleshooting.
While doing this look for good solder joints on all the connections. Make sure the center pins of the big transistors are adequately soldered. Make sure the new wires that connect the boards to the circuit are attached to the correct terminal and pads. Be sure the insulators and hardware that mount the big transistors to the heat sinks have been installed the right way.
After you have confirmed that stuff the check the voltages PB has asked you for and post them here.
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Thanks Paul.
What I meant was since the voltage test result section mentioned that they were done in the 110V environment, does that imply they might be different in a 240V environment. Sounds like no. I will definitely do the voltage tests and post results ASAP.
And is there a list of resistance check test/results for performing after adding the speedball?
See photos. Any advice appreciated (be kind about my sloppy work)
Cheers
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And is there a list of resistance check test/results for performing after adding the speedball?
You need to measure the voltage on terminals 1-10.
I notice from your photos that one of your 270 ohm resistors is cooked. With the older version of your Speedball, it was incredibly common that people didn't properly mount the TIP50s to the heatsinks, and this would cause them to touch and ground out, which would cook that particular resistor. In this case, you can measure the voltage from terminal 12 to each of the metal tabs on the TIP50 heatsink. If you get a low resistance there (under about 100 ohms), then your TIP50 transistors are not properly mounted and you'll need to take the mounting kits off and remount them according to the instructions in the manual.
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you can measure the voltage from terminal 12 to each of the metal tabs on the TIP50 heatsink. If you get a low resistance there (under about 100 ohms), then your TIP50 transistors are not properly mounted and you'll need to take the mounting kits off and remount them according to the instructions in the manual.
@PB: did you mean to write "measure the resistance", not voltage?
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Yes, good catch, resistance!
(That was posted pre-coffee)
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I notice from your photos that one of your 270 ohm resistors is cooked.
I'm lost. I just checked the resistor values on my stone age Speedball. I've got 4 x 22.1k. They are the ones standing upright forming the two pairs. 2 x 31R6 1/8W next to the heatsink. 2 x 150k, one each on the small boards, 2 x 237R also there. Dan's Speedball boards look to be the old ones just like mine.
The center pins on some of the large transistors look like they might not be properly soldered.
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I'm lost. I just checked the resistor values on my stone age Speedball. I've got 4 x 22.1k. They are the ones standing upright forming the two pairs. 2 x 31R6 1/8W next to the heatsink. 2 x 150k, one each on the small boards, 2 x 237R also there. Dan's Speedball boards look to be the old ones just like mine.
The 270 ohm resistors are in the power supply; they are the big white cement resistors mounted by the power supply.
If a tip50 is improperly mounted, it grounds the cathode(s) of the 6080, and the 6080 will draw current until something gets hot until something burns up. That thing that burns up is the 270 ohm resistor that is mounted over the power transformer.
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Thank you, Paul. I'm no longer lost.
I just re-checked the posted images. Did you identify that defect because of the discoloration/blueing on the wire and the slight cracks around the entry point of the wire?
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The writing on the body of the resistor is missing, which usually means it was cooked right off.
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Thanks everyone for your assistance.
You need to measure the voltage on terminals 1-10.
I notice from your photos that one of your 270 ohm resistors is cooked. With the older version of your Speedball, it was incredibly common that people didn't properly mount the TIP50s to the heatsinks, and this would cause them to touch and ground out, which would cook that particular resistor. In this case, you can measure the voltage from terminal 12 to each of the metal tabs on the TIP50 heatsink. If you get a low resistance there (under about 100 ohms), then your TIP50 transistors are not properly mounted and you'll need to take the mounting kits off and remount them according to the instructions in the manual.
Resistance from 12 to 1-10 are all "0L", except 3 which is 0 ohms, and 8 which is 1 ohm.
Resistance from 12 to the fins on the Speedball heatsinks is 0L. Not sure if that's what you meant by tabs?
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When I try to attach photos I keep getting "forum.bottlehead.com is currently unable to handle this request"
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OK, that's a good sign with the resistances, go ahead and move on to voltage checks.
The forum will give that error if the photos are huge, I use a simple resizer to reduce them by 80% or so if they are too big.
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Resistance from 12 to the fins on the Speedball heatsinks is 0L. Not sure if that's what you meant by tabs?
Just checking: when you say you measured resistance between terminal 12 and the "fins" of the heatsink, did you touch the lead to the body of the heatshink itself (big black block of finned aluminum) or to each of the skinny silver legs (what PB called "tabs") that are soldered to the pcb board?
I imagine you did the latter (the legs/tabs), which is what I think PB wanted?, but thought it might be good to be sure.
cheers, Derek
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Just checking: when you say you measured resistance between terminal 12 and the "fins" of the heatsink, did you touch the lead to the body of the heatshink itself (big black block of finned aluminum) or to each of the skinny silver legs (what PB called "tabs") that are soldered to the pcb board?
I imagine you did the latter (the legs/tabs), which is what I think PB wanted?, but thought it might be good to be sure.
cheers, Derek
I actually did both as I was unsure, but same reading either way. Thanks Derek
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OK, that's a good sign with the resistances, go ahead and move on to voltage checks.
The forum will give that error if the photos are huge, I use a simple resizer to reduce them by 80% or so if they are too big.
So do the voltage checks as per the manual? Are they still valid given my cooked 270 ohm resistor?
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The voltage checks will give us a pretty complete picture of what's going on with your amp. It will be helpful in identifying any potential problems, including issues with that resistor, though based on its appearance it is probably still functional.
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The voltage checks will give us a pretty complete picture of what's going on with your amp. It will be helpful in identifying any potential problems, including issues with that resistor, though based on its appearance it is probably still functional.
Thanks Paul. I have to go away for a few days.. just when I was getting excited about this. I'll resume next Wednesday. I really appreciate your taking the time to help.
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OK here goes. They are nothing like the manual.. Voltages at:
1: 0.4
2: 0.01
3: 0
4: 0.005
5: 0.4
6: 0
7: 1.3
8: 0
9: 0.8
10: 0
On a side note. I bought some new leads for my multi meter because the ones it came with didn't have alligator clips. Then I forgot which terminal was which colour. After some quick research I found that black goes in the terminal marked COM (for common I guess?). But then nearly all the readings had a negative in front of them. I read that it doesn't really matter, so I switched the leads around again to test. I left the negative off my measurements above.
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This would be a good time to try and measure the DC voltage of a 9V battery with your meter.
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This would be a good time to try and measure the DC voltage of a 9V battery with your meter.
I like your logic! I was expecting it to be wrong, but I did that and I got 9.6V
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Sorry, I'm going back and forth. By pressing the Range button on the multi meter, I am getting 9.6.
When it was on mV it said 0L.
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Well, 1mV is 0.001V, so you don't want to be on that scale to try to read high voltages. There's probably a 200V setting, that would be what you'd want to be on.
If you were on that setting and the amp was plugged in and turned on and you still got all those zeroes, then your fuse is probably blown.
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If you were on that setting and the amp was plugged in and turned on and you still got all those zeroes, then your fuse is probably blown.
I can confirm the fuse is not blown. I have attached a couple of photos. My meter doesn't have a 200 or 400v scale setting as such. There is a Range button, that cycles through different sensitivities. Basically moving the decimal point, then going into mV.
I've also attached a photo of me testing. Black lead is clipped onto 12 and I'm touching 1 with red lead. Can anyone see anything I'm doing wrong?
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Your meter uses its "Auto Range" capability to adjust to the voltages that it finds. It will jump to hundreds of Volts when it needs to and down to mV when you are measuring much lower voltages. You will always be at the correct setting by virtue of that function.
It looks like you are measuring 190 VDC in your picture. I can't tell from the picture, if there is a decimal point somewhere, because you focused on the probes and not the meter.
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What is the stain on the chassis between the PT and the octal? It may be totally unrelated to your issue, but it's worth asking.
With your meter set to AC volts, what AC voltage do you get between terminals 1 and 2 on the power transformer?
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The B numbers are written on the "stain" so likely a left over from painting the topside. Note paint runs around the edges of the plate.
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It looks like you are measuring 190 VDC in your picture. I can't tell from the picture, if there is a decimal point somewhere, because you focused on the probes and not the meter.
Thanks. I'm pretty sure it was 0.19, but I'll check again.
What is the stain on the chassis between the PT and the octal? It may be totally unrelated to your issue, but it's worth asking.
With your meter set to AC volts, what AC voltage do you get between terminals 1 and 2 on the power transformer?
Yes, the stain was just from painting the other side. Assuming you mean 1 and 2 as per the attached diagram, I got 239V AC.
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How about the other pairs of terminals on the power transformer?
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How about the other pairs of terminals on the power transformer?
So Paul do you mean like between 3 & 4, 5 & 6 etc? or what?
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V AC Between:
3 & 4: 5.8
5 & 6: 168.4
7 & 8: 168.1
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What DC voltage do you get between terminals 20 and 21?
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What DC voltage do you get between terminals 20 and 21?
239
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How about between 14 and 15?
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How about between 14 and 15?
7.2 mV
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OK, despite it looking OK, it seems very, very likely that the 270 ohm resistor that runs across the power transformer is blown open. It's either that, or one end of that resistor is not soldered, or the black wire that runs next to it is not well connected.
With that resistor open, that first 220uF power supply cap will stay charged up. You can use a screw driver with a well insulated handle to short its terminals to remove its charge, or check out a YouTube video on discharging a capacitor with a resistor.
-PB
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OK, despite it looking OK, it seems very, very likely that the 270 ohm resistor that runs across the power transformer is blown open. It's either that, or one end of that resistor is not soldered, or the black wire that runs next to it is not well connected.
With that resistor open, that first 220uF power supply cap will stay charged up. You can use a screw driver with a well insulated handle to short its terminals to remove its charge, or check out a YouTube video on discharging a capacitor with a resistor.
-PB
"Dan's memorial service will be held at... " ;D
So you mean the one in the attached photo? So I need to short between 20U and 21U?
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Yes, precisely. This is not a lethal amount of energy thankfully. When the cap is discharged, you can use your meter to check the resistance of that 270 ohm resistor.
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OK. I did that. Even after a few hours, there was still over 200V in that capacitor. How long will they hold charge like that? (just out of curiosity).
I got a huge spark which scared the crap out of me, but then I tested it and it was almost completely drained. I couldn't seem to get it to zero. Even with more shorting it still had a volt or two.
I measured the resistance across the 270 ohm resistor and it was 0L.
I also noticed it now has a hairline crack right across it. I'm not sure if that was there before. See attached.
So what now?
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I just noticed the Forum clock is wrong. It says 5:55, and it's 8:55 there isn't it?
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Yes, the charge will stay there for a long time, that's why you use the screwdriver to drain out the charge.
If you started with a perfectly working Crack, then put the Speedball in, then cooked that resistor, then the TIP50 transistors are unlikely to be properly mounted. I know I've mentioned this before, but it's really important and if it's still an issue when you put the new resistor in, then you'll just get to do this all over again.
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OK. Thanks Paul. So do you think I should remove the TIP50s and re-solder them?
Someone else mentioned a while back they thought it looked like centre pins on some other transistors were not soldered. Are there any other resistance or voltage checks I can do to make sure the speedball boards are assembled correctly?
As you say, and I keep thinking this, the Crack was working perfectly, so it must be something I did in the speedball installation.
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The TIP50 issue isn't a soldering issue, it's an issue where the hardware used to mount the TIP50s to the heatsinks isn't properly installed.
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Just in case you've lost track of things. The TIP50's need to be insulated from the heat sinks. Earlier in the thread he provided one way to test this by checking the resistance from the metal tab on the TIP50 to a ground point such as terminal 12. It may also work by checking the resistance from the metal tab to the heat sink itself.
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Just in case you've lost track of things. The TIP50's need to be insulated from the heat sinks. Earlier in the thread he provided one way to test this by checking the resistance from the metal tab on the TIP50 to a ground point such as terminal 12. It may also work by checking the resistance from the metal tab to the heat sink itself.
Thanks. That was a timely piece of advice.. I was unsure.
The resistance is 0L from all 6 "legs" of the TIP50 to Terminal 12. See attached.. clipped onto 12, touching TIP50 (just in case there is any confusion)
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OK, when you get that 270 ohm resistor replaced, you can start by just firing the amp up with the 12AU7 and no 6080. That will take the big board out of the circuit and let you test the small PC boards up front and the 12AU7. The voltages on terminals 1-5 will look mostly correct, with terminals 2 and 4 being a bit on the high side.
Another funky thing that could have happened to your amp would be if the keyway broke off on the bottom of your octal tube, and then it got inserted improperly. This can create all sorts of weird problems and a toasted power supply resistor is certainly an option.
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OK, when you get that 270 ohm resistor replaced
Thanks Paul. Does this look OK as a replacement? Says 270 ohm, 5 watt.
https://www.jaycar.com.au/270-ohm-5-watt-wire-wound-resistor/p/RR3284
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The Xicon 270 ohm 5W resistor should be available from Mouser Australia. It has leads that are long enough to reach across the terminal strips.
Failing that, just about any 270 ohm 10W resistor will also fit in that space and the leads will be long enough to reach the terminal strips.
I'm not sure that the one you linked to would reach across.
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Failing that, just about any 270 ohm 10W resistor will also fit in that space and the leads will be long enough to reach the terminal strips.
OK. I'll look for the Mouser one. I thought the one I was replacing was 5W?
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I thought the one I was replacing was 5W?
It is. A 10W resistor will have a longer body, so the short leads won't be an issue.