Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: Johnman1116 on June 20, 2012, 11:13:36 AM
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Resistance:
Terminal: Me: Bottlehead
1: 1: *
2: 1: *
3: 0: 0
4: 1: *
5: 1: *
6: 2.4: 2.4
7: 2.8: 2.9
8: 0: 0
9: 2.8: 2.9
10: 2.4: 2.4
12: 0: 0
13: 1: * to 270
14: 0: 0
20: 0: 0
22: 1: 0
B3: 2.8: 2.9
B6: 2.8: 2.9
RCA
GND: 0: 0
Center: 86.3/96.2: 2.9/2.9
I am thinking that something is not connected fully but is lame because i checked everything with a continuity reader.
I have applied the revisions: terminal 4 to 14U, but not the start up voltage mod.
also probably a very dumb question but it doesnt matter if i use the lower or upper terminals right? I figured out what those U's and L's halfway through lol.
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Edited:
Assuming that the "1" reading is an infinite reading, the only readings that are off is the 22nd terminal and possibly the 13th.
The thing is there is nothing attached to terminal 22 so a reading of "1" would make sense, in this case being an open circuit.
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First, lower and upper terminals are connected with metal. They are one and the same when measuring resistance and voltage. However, when measuring resistance first touch your meter leads together. This is not going to be zero and is the resistance of your meter leads. Subtract it from the readings that should be zero. If you get something under one ohm consider that zero.
It is always a good practice posting the expected and those measurements that are greater than 15% out of spec.
Also, a good read:
http://www.bottlehead.com/smf/index.php/topic,1667.0.html
When you whittle it down to only the out of spec readings it will be easier to help.
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Those 1s probably mean "I" = infinity, i.e. a very high resistance reading. It's always worthwhile to take some time to learn how a given meter indicates various readings.
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WOW so sorry, I was completely unspecific on my problems. Yes I know about the 15% margin of error. I was actually going to post only my problem readings but I thought you would have preferred all of them.
The readings that are bothering me are the ones that are "1": 1,2,4,5,13 and 22. I thought a reading of 1 was either the setting is too low or the circuit was open.
I went through the manual and did not see anything about "Infinity" but I thought that that just meant the circuit was open therefore the resistance is infinite.
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Very lo res those seven segments, so numeral 1 and capital letter I look the same. Some meters say "OL" instead, which I guess means "over limit". Easier to understand anyway, as you only see that when you read something too high for the scale setting. One of the difficulties for us as a kit manufacturer is that there is not a standard display for these readings on DMMs (and some folks still use analog scales). So we can't just say "if the meter says 'OL' the reading is very high resistance or open" and assume that everyone will grok it.
Anyway, it's a lot easier for folks here to troubleshoot if they just see the terminal readings that are off. Otherwise we have to sort through all the readings and figure out for ourselves which ones are off before we can get to offering suggestions.
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basically you are saying that I can move on?
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I'm saying that if you have any resistance readings that are not to spec with the manual let us know what they are, what the value is supposed to be, and what terminal you measure them at. If they all are in spec, assuming that the 1 you see is an "infinite" reading, you are good to move on.
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edited.
From the manual:
Overrange "1 or -1" is displayed
"1 = OPEN or infinite"
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Some meters really act funky when measuring resistance where a capacitor is connected. Im sure you are aware thats what those * symbols are in the manual. All my meters act a bit differently when measuring those terminals. I have 3 meters, none of which are great. When in doubt with one, I just break out a different meter and usually get an answer that inspires enough confidence to move forward.
As I think was mentioned, you could read 1 ohm or even a couple of ohms due to the meter leads. Some meters have a zero function to zero out the small resistance that the leads add. Others, you have to subtract when measuring very low resistance. Looking at T22 in your measurments, your meter is reading "1". So, is that 1 ohm or infinity ? ;D If it's 1 ohm, there probably isnt anything to worry about.
T13, Im not sure what to think because you meter looks like it measured 1=infinity for some of the */capacitor measurments but that terminal is a little different because the manual states that it will fluctuate in that it should climb slowly to about 270K ohms. Again, your meter may just act funky because of the capacitor. I would try taking that reading a couple different times making sure you have real good contact with the terminals (preferably using some lead clips).
I know, not much help. Sorry. Im not at all an expert in these things so I cant give a definitive go or no-go to the voltage checks.
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VOLTAGE
Terminal - Me - Bottlehead
1- 150- 90
7- 150- 100
A6- 150- 90
A8- 12.9- 1.5
Also I do not see the 12AU7 (smaller tube) light up but maybe I am mistaken. Also I do not see both LEDs light up. The one from middle to A8 does not.
Thanks,
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Looks to me like the LED at A8 is in backwards.
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Everything looks fine to me.
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You're voltage is good at B1? Double check.
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Everything looks fine to me.
Yup, installing them upside-down helps clear that up easily.
Looking at my schematic yesterday it seems that one side is not conducting. You do have voltage at the plate of the driver tube so the circuit is clear to that point. Usually it means that the cathode circuit is open somehow. Try this, set your meter either to the lowest resistance setting or the diode setting.
This will test the diodes. Measure resistance from the pin on the tube socket to terminal 3. This doesn't touch the diode leads and proves the solder joints are good.
Measure one diode from tube pin 3 to T3, then swap the leads and measure.
Measure the other diode from tube pin 8 to T3, then swap the leads and measure.
In both cases above you should get a high resistance measurement one way and a low one the other way. Since you have two diodes right there it will be easy to compare one channel to the other.
Edit:
If you find one or both LEDs open, infinite resistance, both ways retouch the solder joints. By that I mean wet the soldering iron, touch it to the tube pin or center pin or terminal at ground (T3?) and when you see it become liquid count 1..2 and remove the soldering iron. So just liquid and the heat off. Too much heat can fry the LED.
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Well I did the diode test and tested the leads of the LEDs. The one connected to terminal 3 was fine (infinite one way and about 1.5 the other). The LED connected to terminal 8 was open and I touched them up using your method but still no go.
Do I need a replacement?
Thanks Grainger.
VOLTAGE
Terminal - Me - Bottlehead
1- 150- 90
7- 150- 100
A6- 150- 90
A8- 12.9- 1.5
B1 - 150 - 90
B3 - 150 - 100
Thank Laudanum.
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Call Bottlehead, Eileen will send you a replacement LED. Unfortunately, the LED's used arent common Radio Shack stock.
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In that case, the diode must be damaged. Email Eileen for a replacement.
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Got to be kidding me... I think I am CURSED! :'(
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Apologies. We have a new staffer who didn't know that we ship those in padded envelopes. A new pair are headed to you tomorrow.
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No worries, I actually was not blaming you guys at all and just thought it was a case of bad luck. Anyways the next batch of LEDs work flawlessly and all my resistance and voltages measurements checked out (nothing more that 12%).
I do still have some problems. I am getting lots of background noise which include I guess a high pitch buzzing and a lower pitch buzzing that is more "dirty" sounding; As in its sort of crackling buzz and not a smooth buzz.
I have let the amp warm up, used different sources, rca cables and power outlets but no change. I do not hear it when the volume is all the way down but as soon as i raise it, I get problems. I have not tried other headphones though...
I did check my solder joints as I was building the Crack and tested multiple times with a continuity test. I could check one more time perhaps and maybe heat up the joints again but I am fairly confident that that is not the problem.
This leads me to believe it may be a tube problem. The smaller 12au7 tube doesnt appear to light up, from what I can see, but it does get hot (yea I touched it) and I am assuming it working because the amp basically works. Maybe I could try cleaning the tube contacts but yea, I do not really know much about tubes. I have heard about noisy/faulty tubes but I do not know how frequently that happens. Could this be an issue of burn in? I dont know.
Your advice would be much appreciated.
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And THANK YOU for a great project. I got to things that I have never done such as applying finish to wood and spraying Hammertone which was really cool. It is nice to look back and feel accomplished and explaining to my friends that this is not a lamp :)
Troubleshooting is all apart of the journey and atleast I did not have to do any major desoldering and reconfiguration or get electrocuted.
Thanks again.
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Johnman1116 ... The 12AU7 may have spiral filaments. I think the EH 12AU7's do in fact. These tubes dont glow like a lot of others. Im not using any right now in any of my gear but from memory, I think you should probably be able to see some glow if you look down the top of the tube. Point being, just because the tube doesnt appear to be glowing, doesnt necessarily mean it's a bad tube or the cause of your noise. It may be the cause, glowing or not. Or, it could be the 6080 that is noisy. Or it may not be tube related.
Since your resistances and voltages checked out, I would probably try swapping tubes to see if you have a noisy one. It's quick and easy. But you may get advice from the gurus for other things to look for. Regardless, it's always a good idea to have a spare or two of each tube. Even if they arent expensive, boutique tubes. 12AU7 and the 6080 (or 6AS7) tubes can be bought inexpensively. I would consider getting a spare or two of each. Even if it doesnt turn out to be a noisy tube, you will probably find yourself needing one of the spares at some point. Good to have on hand for replacement without down time (waiting on a tube to be shipped to you) and quick troubleshooting.
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Oh yes, I will get a spare tube of each and see if swapping them changes anything and post my findings.
Thanks,
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From the description, the noise could be radio noise picked up from the environment. Cell phones are notorious for this, but there are increasingly many sources of radio signals - flourescent lights, light dimmers, refrigerators, computers, anything with a switching power supply, ...
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Well... regardless I bought one tube of each.
A Sylvania 12au7a and a Raytheon 6080WB. Hopefully the problem goes away.. I am at a different location and will have to see if it changes anything.
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So at my new place, it is dead silent from 0 to max volume with the exact same setup.. interesting.
COOL!!!
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Well good then. Now you have a couple of spare tubes coming and a quiet amp. Paul must have been right, as usual. Must have been picking up interference from something in the old place. Sounds like you are all set to enjoy some tunes ;)
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A few posters have noise in their Crack when they startup. Burning in gets rid of that for some, not all. But the majority of builders get a dead quiet Crack from the get go. And those are the words they use, "Dead Quiet."
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So I have run into they same type of buzzing again. This time I think I know where the problem is coming from. It seems like when I inset and remove the RCA, it becomes loose. I remember this happening last time as well but tightening it did not fix it.
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John,
You can replace the RCA jack(s) cheaply and easily.
http://www.parts-express.com/pe/showdetl.cfm?&Partnumber=091-1120
If there is something loose, it is probably the center conductor which can get overheated easily.