Resistance Check later followed by a voltage check :)

J

Johnman1116

New member
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.
==================================================
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.
 
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.
 
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.
 
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.
 
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.
 
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.
 
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. 
 
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,
 
Johnman1116 said:
Everything looks fine to me.
Click to expand...

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.
 
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.
 
Call Bottlehead, Eileen will send you a replacement LED.  Unfortunately, the LED's used arent common Radio Shack stock. 
 
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.
 
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.
 

Attachments

You must log in or register to reply here.

Similar threads

C
Troubleshooting Help [resolved]
Replies
4
Views
211
Crackerjk41
C
F
  • Sticky
Failed Final Voltage Check
Replies
9
Views
5K
Paul Birkeland
Paul Birkeland
P
Resistance Check Question [resolved]
Replies
5
Views
3K
pbvoorhees
P
C
Resistance check errors
Replies
10
Views
4K
Colman
C
E
Weird voltage readings and leds do not light up
Replies
11
Views
4K
Paul Birkeland
Paul Birkeland
Back
Top