Author Topic: BK Precision 2120 trace issues  (Read 6538 times)

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Online bdunham7

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Re: BK Precision 2120 trace issues
« Reply #150 on: March 18, 2021, 10:53:07 pm »
DS212 arrived, it has built-in signal generation (square, sine, saw, from 10hz to 1mhz) and proper 10x attenuation support. I'm guessing I should hook the output channel of the 212 to the external trigger of the 2120 (dangerous potential for typos here) using a 10khz square wave, then connect the ground of channel A to the output channel ground and probe the points? Additionally, should testing be done with the 2120 on or off? It's been long enough that I don't remember how I was testing it.

Yes, that sounds correct, 2120 on, but be careful and use 10X all the time.  Also, I don't think you need to worry about connecting grounds since all the BNC shells on the 2120 are grounded.
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline vexatag

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Re: BK Precision 2120 trace issues
« Reply #151 on: March 18, 2021, 11:27:29 pm »
In that case I should connect the 212 input probe to the chassis, yeah?
 

Online bdunham7

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Re: BK Precision 2120 trace issues
« Reply #152 on: March 18, 2021, 11:38:29 pm »
I'm not familiar with the DS212.   I had a quick look and I'm not sure how it connects.  Can you use your BNC scope probes with it?  Does it need/have an adapter for those?  Or are those connectors on the DS212 actually BNC somehow?
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline vexatag

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Re: BK Precision 2120 trace issues
« Reply #153 on: March 18, 2021, 11:44:58 pm »
The connectors aren't BNC, but they're easily adapted. I bought one adapter (should have bought two) and it came with one compatible lead.
 

Online bdunham7

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Re: BK Precision 2120 trace issues
« Reply #154 on: March 18, 2021, 11:49:47 pm »
The connectors aren't BNC, but they're easily adapted. I bought one adapter (should have bought two) and it came with one compatible lead.

OK, then you should be good to go.  The signal to the EXT trigger can be the compatible lead and you can probe with the BNC adapted lead set to 10X.  Just don't go near the high voltage like the other guy...
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline vexatag

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Re: BK Precision 2120 trace issues
« Reply #155 on: March 18, 2021, 11:54:14 pm »
Yeah haha, gonna check each point with my multimeter first.
 

Offline vexatag

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Re: BK Precision 2120 trace issues
« Reply #156 on: March 19, 2021, 02:46:27 am »
pins 3, 5 and 5 of U603.

Which other pin did you mean here?
EDIT: Judging by the other BK owner's thread I'm assuming you want me to test pins 3, 5, and 6 on U603.

Extra edit: tested S601, the two end pins have triangle waves depending on the switch position. I have screenshots if you would like. As for U601 pin 9, there's not enough signal to pick up even at a low voltage scale (is that the correct term?). Testing U603 now, will update with my findings.

Third edit: U603 pin 3 had a triangle wave, pins 5 and 6 just had noise.
« Last Edit: March 19, 2021, 03:12:39 am by vexatag »
 

Offline vexatag

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Re: BK Precision 2120 trace issues
« Reply #157 on: March 22, 2021, 02:01:33 am »
Here are the screenshots, the first two are the switch pins and the third is U603 pin 3. I also ordered two more BNC adapters.

Side note, the 212 has a math channel with a-b mode, so I could easily use it as a differential scope if that would be useful or relevant at all.

Secondary side note, I tested the calibration point on the 2120 and it seems to be working.
 

Online bdunham7

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Re: BK Precision 2120 trace issues
« Reply #158 on: March 22, 2021, 02:25:39 am »
Screenshots are good.  I need to figure out what those translate to as far a scale.

Can you show pins 5 and 6 of U603?  How much noise?

Edit:  Just for reference, can you show pins 7 and 14 of U603?  Should be ground and 5V, but I just want to see where they are.
« Last Edit: March 22, 2021, 02:34:10 am by bdunham7 »
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline vexatag

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Re: BK Precision 2120 trace issues
« Reply #159 on: March 22, 2021, 02:33:33 am »
I'll retest things later this evening with measurements onscreen (forgot to set them up last time).
 

Offline vexatag

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Re: BK Precision 2120 trace issues
« Reply #160 on: March 22, 2021, 04:45:55 am »
Ok, here are screenshots of the pins being tested.
Screenshot order:
  • Switch pins when active
  • U601 pin 9
  • U603 pin 3
  • U603 pins 5 and 6
  • U603 pins 7 and 14
If needed, I can check the pins again in 1x mode because there's something fishy going on here.
 

Online bdunham7

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Re: BK Precision 2120 trace issues
« Reply #161 on: March 22, 2021, 06:05:24 am »
Is the scope turned on??? 
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline vexatag

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Re: BK Precision 2120 trace issues
« Reply #162 on: March 22, 2021, 06:06:45 am »
Yeah, scope is on.
 

Online bdunham7

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Re: BK Precision 2120 trace issues
« Reply #163 on: March 22, 2021, 06:14:33 am »
OK, on U603, pin 7 is ground, pin 14 is 5 volts.  Use your multimeter and see if that is so.  If so, then you have to figure out why your scope doesn't show you that in those measurements--and the 10X setting is not likely to be the cause, so leave that at 10X for now to avoid any calamities.  If you don't have proper power supply to U603, then we have a different issue somewhere.  You checked all the power supplies way, way back, right?
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline vexatag

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Re: BK Precision 2120 trace issues
« Reply #164 on: March 22, 2021, 06:26:47 am »
OK, on U603, pin 7 is ground, pin 14 is 5 volts.
Pin 7 goes to ground, pin 14 measured around 4.3 volts.
You checked all the power supplies way, way back, right?
I checked the power supplies at the beginning of this process, yeah.
 

Online bdunham7

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Re: BK Precision 2120 trace issues
« Reply #165 on: March 22, 2021, 06:03:18 pm »
OK, let's back up (again) and make sure your new scope can give you a proper reading.

Are you not using a ground clip on the scope probe?  I believe I may have told you not to, but I'm not familiar with your little scope and it may have isolated inputs, so lets try this:

1) Don't use the signal generator at all--disconnect it and set the leads aside
2) Use the LINE trigger setting on the BK2120
3) Use one probe on the scope and connect the ground clip securely, preferably to one of the BNC shells or alternatively to the frame of the instrument.
4) Try again, starting with pins 7 and 14 of U603.  You need to be able to see 0 (or so) volts and 5 volts (4.3 is probably OK) just as your multimeter shows before proceeding.
5) If that works, start looking for the 60Hz line trigger signal, starting again at the switch pins, then pin 9/U601 and pin3/U603.  Screenshots are needed here.
6) If those look good, then pins 5 and 6 of U603.
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline vexatag

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Re: BK Precision 2120 trace issues
« Reply #166 on: March 22, 2021, 07:56:06 pm »
I have been using the ground clip on the new scope, yes. Additionally, I've stopped using the external signal generator and have instead been using the new scope's built-in function generator.

The first two screenshots are from the slope switch with coupling set to LINE. When the ground cable was connected to the chassis, I got 4.3 volts to show up on pin 14 once in like 20 minutes of testing at various timebases, however when I checked without the ground cable connected I instantly got a reading. That reading is in the third screenshot. Going to hold off on testing the rest of U603 and pin 9 of U601 until you've had a chance to analyze this information.
 

Online bdunham7

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Re: BK Precision 2120 trace issues
« Reply #167 on: March 22, 2021, 08:20:49 pm »
Is there an option in that scope for AC and DC coupling?  Pin 7 of U603 should be a more or less flat line at about the level of the A channel marker and pin 14 should be a flat line about 5 volts (2.5 divisions) higher than that.
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline vexatag

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Re: BK Precision 2120 trace issues
« Reply #168 on: March 22, 2021, 08:25:51 pm »
Is there an option in that scope for AC and DC coupling?
The DS212 has AC/DC coupling, yes. I've been using AC coupling in all the readings so far.

Pin 7 of U603 should be a more or less flat line at about the level of the A channel marker and pin 14 should be a flat line about 5 volts (2.5 divisions) higher than that.

Just checked this in DC coupling and you're correct. Going to go ahead and check the remaining pins in DC coupling.
« Last Edit: March 22, 2021, 08:34:56 pm by vexatag »
 

Online bdunham7

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Re: BK Precision 2120 trace issues
« Reply #169 on: March 22, 2021, 08:35:34 pm »
Change to DC coupling and try all that again!
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline vexatag

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Re: BK Precision 2120 trace issues
« Reply #170 on: March 22, 2021, 09:37:46 pm »
Order of the screenshots: Slope switch pins (two images), U601 pin 9, U603 pins 3, 5, and 6.
 

Online bdunham7

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Re: BK Precision 2120 trace issues
« Reply #171 on: March 24, 2021, 02:37:43 am »
I don't know why you don't have a signal at U601 pin 9, but have it at U603, pin 3.  That seems strange.

Nonetheless, the problem appears to be that U603 isn't switching, even though it has an input that should switch it.  I'm probably not going to be able to think about this for a day or two, but in the meantime, you can try scoping every pin of U603 and posting all the screenshots.  I think you are getting close to the problem area.
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline vexatag

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Re: BK Precision 2120 trace issues
« Reply #172 on: March 26, 2021, 05:07:49 am »
Sorry this took a few days, I just got a vr headset so that's been using a lot of my time. Here's the screenshots of U603's pins, I hope a zip file isn't too suspicious for you.
 

Online bdunham7

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Re: BK Precision 2120 trace issues
« Reply #173 on: April 14, 2021, 03:49:14 am »
I may have forgotten about you!  Where were we on this? 
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline vexatag

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Re: BK Precision 2120 trace issues
« Reply #174 on: April 19, 2021, 12:51:28 am »
We were looking at U601 and U603, I scoped every pin of U603 and put the screenshots in a zip folder
 


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