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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Dec Thu 10, 2020 7:16 am 
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Location: St. Louis, MO
Notimetolooz wrote:
I tried to find a pdf manual online but I didn't come up with one.


https://beyondmeasure.rigoltech.com/act ... ide_EN.pdf

That's for the whole DS1000Z series, but mine is the DS1054Z.


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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Dec Fri 11, 2020 1:37 am 
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Notimetolooz wrote:
I tried to find a pdf manual online but I didn't come up with one.
I also looked at many videos that explained reading a DC level on a scope and it was very tough to find a good one,
hardly any explained it well if at all when using a digital scope. It is so basic that it is taken for granted everyone knows.
The thing is, you need to figure it out by counting the grid (graticule) lines and knowing how many volts per line space, like reading a ruler. That's the way people measured things on a scope before they got computerized scopes.
Here is a video that kind of shows it.
https://www.youtube.com/watch?v=8VEg6L2QG5o
However, looking at your scope screen I think I figured out what might work for you. You should learn to read the graticule though.
I think the markers on the left of the screen that identify the traces are at the zero level for that trace. When you have AC coupling on that trace the zero level is at the middle level of a symmetrical sinewave. If you have the trace on DC couple then the zero level is ground level. So if you have DC coupling on a trace you can find the DC level by measuring the distance (graticule) from the identifying marker to the trace and multiplying by the volts per division for that trace.
Incidentally, the red marker on the right of the screen, marked with a T, is the trigger level.
I also think I figured out a lazy way for you to find the approximate DC level. You have to use DC coupling,
I think the Vmax reading will give you that value if the voltage is positive and the Vmin reading will give you the value if the voltage is negative.

The way you split up the signal generator output is OK for low frequencies, but it is wrong when it comes to RF.
Each one of those coax cables (at RF) that you have branching out is a transmission line and therefore
should be terminated correctly. However if you did that it would be too much load on the generator and also the generator wouldn't see a 50 ohm load. In other words, you can't branch coax like that if the signal is at RF.
The detector probe isn't a 50 ohm load, a 10X scope probe isn't 50 ohm load, so you don't want to have a coax feeding them. You could have a 50 ohm coax going between the generator and 50 ohm termination, but the detector probe and the 10X scope probe should be at the 50 ohm termination. That is why I recommended you use a T at the 50 ohm termination (an inch or so won't be a problem). Welcome to RF, you can't hook things up like you can with DC or audio circuits. You could also use two lengths of coax with a T between them, attach that T directly to the scope BNC for that channel. The other end of one coax is connected to the generator. The other coax's end would go to another T with the 50 ohm termination and the detector probe.
I think most of the reason for the better trace is you not using the clip lead. The clip lead was acting like an antenna. Maybe the coax is better shielded.
You shouldn't be seeing much AC on the detector probe output, maybe it is ripple.


Attenuation is also settable on my scope as well. It's really handy! As long as that channel is set to the same as the probe, the scope will do the math so that the units are correct. I had it set at 1X to match the SG since it had no attenuation.

You know what? Let me grab a battery and check out that Vmax function as well as a few others. That's a definite DC source. We'll see what matches my DMM.

edit: Hey, you're right! Vmax it would appear that Vmax does indeed match DC voltage. I just tried with an AA battery I had lying in a drawer. My DMM says it's 1.52 volts DC. When I try it with my scope and hit the Auto button, it says Vmax is 1.53 V. I see what you mean about reading the graticule too. Hitting the Auto button zoomed in far enough to pick up stray... whatever in the room, enough to make a wave. The vertical scale was 5mV. So I zoomed out until the vertical scale was 1 V, then moved the vertical position to 0 volts. Sure enough, the trace is about one and a half squares above 0 volts.

...but when zoomed out, the Vmax changes. So I brought up a few more stats and put them in the picture too. You know, 1.52 volts would be 0.08V right between Vmax and Vmin...


Attachments:
AA battery test.png
AA battery test.png [ 37.83 KiB | Viewed 1191 times ]
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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Dec Fri 11, 2020 2:26 am 
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Location: Dallas, TX
Yes, I was going to say that on page 46 of that pdf it explains about the input channel coupling. It switched between AC, DC, and GND. It wouldn't have the DC coupling option if it didn't display a DC level.
I looked for something that would do "AUTO Triggering" that causes the triggering to "free run" like an analog scope but I couldn't find that. The "AUTO" button is not the same thing. You may have to set the triggering to "AC LINE" (page 68) which is the power line 60Hz signal just to get the display to work.

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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Dec Sat 12, 2020 12:39 am 
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Location: St. Louis, MO
Notimetolooz wrote:
You may have to set the triggering to "AC LINE" (page 68) which is the power line 60Hz signal just to get the display to work.


Could you elaborate on this?

Also, what's the verdict on the probe I built? Does it look like it works right? I remember reading in the 415 book to set my VTVM for negative voltage when aligning the 415, so at least that part is correct.


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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Dec Sat 12, 2020 2:34 am 
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ZombieElvis wrote:
Notimetolooz wrote:
You may have to set the triggering to "AC LINE" (page 68) which is the power line 60Hz signal just to get the display to work.


Could you elaborate on this?

Also, what's the verdict on the probe I built? Does it look like it works right? I remember reading in the 415 book to set my VTVM for negative voltage when aligning the 415, so at least that part is correct.

I wasn't sure the scope would display a pure DC level, so in able to make sure you could trigger on the 60Hz power line just to get it to trigger and enable the display. You don't have to display a trace from where you get the trigger from.
It seems the scope might be triggering on the ripple noise it seems to see on the battery.
The ripple shouldn't be there. Maybe your cable or scope probe isn't shielded well enough.
I don't know why it is changing the Vmax when you zoom.
The output of the detector probe should be DC if there is no modulation on the RF.
You were seeing some ripple, and the DC level wasn't evident so I don't know that the probe is working right. It could be that you had AC coupling on the channel fed from the detector probe and the sensitivity to high.

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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Dec Fri 18, 2020 1:48 am 
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They're the probes that came with the scope.

Here's the output for that battery, but with the trigger on the AC line like you were talking about. To me, that still looks noisy. I even took the probe off the battery. It's noisy even at 0V.


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AC trigger.png
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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Dec Fri 18, 2020 3:18 am 
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Well on the bright side you figured out how to see the DC level on the scope.
The 160mV or so noise seems to be more than you should see on the battery.
The scope is adding the noise RMS voltage to the DC level (DC=RMS) when it calculates the RMS it displays, that makes sense.
Try connecting the ground wire on the scope probe directly to the tip of the scope probe. There should be very little noise pickup that way.

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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Dec Fri 18, 2020 3:55 am 
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Tip to ground, as requested. 1X both scope and probe if it matters.


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tip to ground.png
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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Dec Fri 18, 2020 6:16 pm 
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That doesn't look very impressive to me.
I figure it this way, analog scopes are read by judging the distance according to the scale marks.
The width of the trace-line is about 1/20 of one division, so if the scope is set to 1V per division then the line is about
50mV wide. Any noise less than that couldn't be seen. When you connect the probe ground clip to the probe tip using
an analog scope set to 1V/div you will see a straight line. No noise.
Some things to try;
Check if the other channels show the same thing.
What does the noise measure when you use higher sensitivity? If you see something like 80mV on the 10mV/div setting, I think that is a problem.
Maybe start another thread asking if people with the same scope see something similar. Maybe it is just what that model scope does.
Is your scope still under warranty?

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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Dec Sat 19, 2020 12:30 am 
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Location: St. Louis, MO
Notimetolooz wrote:
Is your scope still under warranty?


It should be. I bought it about this time last year and it has a 3 year warranty.

It's almost dinner time. I'll get you those test results after dinner.


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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Dec Thu 24, 2020 10:19 pm 
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Joined: Jul Mon 01, 2019 4:42 pm
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Location: St. Louis, MO
Notimetolooz wrote:
That doesn't look very impressive to me.
What does the noise measure when you use higher sensitivity? If you see something like 80mV on the 10mV/div setting, I think that is a problem.


Here are 1X and 10X, both scope and probe. Does this look normal?

In other news, it looks like my probe works! I'm still doing section 12.4.1 in the book. I plugged my probe into my VTVM and I'm getting negative DC voltage... barely. The book references using the B&K 177 VTVM, which apparently goes down to 0.5V DC for its range. My Heathkit IM-11 on the other hand only goes down to 1.5V. I need to turn on at least 3 markers to get the needle to move, but it moves! Now I just need to find my alignment tool to turn those slugs...


Attachments:
1X.png
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10X.png
10X.png [ 37.13 KiB | Viewed 1092 times ]
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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Dec Fri 25, 2020 1:38 am 
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Hummm.
Maybe your scope probes are not shielded very well, or there is a poor connection somewhere on them.
I can set my analog scopes on the same 10mV sensitivity, connect the probe ground to the probe tip and see a nice quiet flat line. 10X or 1X probe show the same.
I don't know if this is just the way that scope model is or it has a problem. I guess you should ask someone else that has that scope.
Obviously if you wanted to look at a small signal you would have difficulty telling the noise pick-up from the true signal.

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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Jan Tue 05, 2021 6:44 pm 
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Ugh, I hate this thing. So the marker for 39.75 MHz died. I'm pretty sure that it's the crystal. I swapped in a crystal from a higher Hz marker into the 39.75 circuit and that marker came alive again. Conversely, I swapped that suspect 39.75 crystal into that other marker's circuit and it also disappeared.

So where do I get a replacement 39.75 MHz crystal? I found this on Ebay, but the pins look bigger. https://www.ebay.com/itm/CTS-Knights-Mo ... 4208692594 I'm guessing the pins are more rigid for a socket, not soldered in directly like mine? I don't know much about crystals. From some quick googling, they appear to be different package sizes out there?


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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Jan Tue 05, 2021 7:17 pm 
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If you're sure the xtal is dead, try rapping it on the desk once or twice. It'll either come back to life, or you've lost nothing by trying.

I think there was some earlier thread on trying to get the correct crystals for these things. You'd have to know the specs of the original. Fundamental, harmonic, which overtone. ... all that fun stuff. If it's in the wrong size can, you can probably swap it into your dud can with some extreme care though.

It may be worth keeping your eyes open for another unit to be a parts donor. They are usually dirt cheap, but shipping is usually a deal killer. However they are not particularly rare, and you may stumble across one when you least expect it. They show up at swap meets, electronic flea markets, and usually a few every year at the ETF museum auction. Prices are generally $25 or less for a non working one.

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Last edited by Barry H Bennett on Jan Tue 05, 2021 7:42 pm, edited 1 time in total.

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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Jan Tue 05, 2021 7:37 pm 
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Location: Dallas, TX
There were many styles of crystals over the years. FT-243, HC-6/U, HC-13/U, HC-17/U, etc. are all plug in-style.
That one on ebay is a plug-in style.
Many times plug-in crystals are used to receive set frequencies in CB and similar radios. I think this is one of those. Some sweep generators have a crystal socket on the cabinet for markers, it could be for that. If you tried to solder the larger pins to a board the heat may damage the crystal.
Also you have to be careful about crystals used in radios, sometimes the frequency marked on it is the received frequency which is offset from the actual crystal frequency by the radio IF frequency (455KHz, 10.7MHz, etc.).
If you were looking for radio crystals, this might be a place to try.
http://www.nu-tronics.com/Parts.html

By the way, what have you found out about the scope noise?
I thought you might try putting a BNC terminator on the scope channel input and see if you see noise, 50 ohms would be close to a short on the input.
Also is the noise still there when you select GND for that channel on the menu?

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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Jan Tue 05, 2021 8:17 pm 
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Notimetolooz wrote:
If you tried to solder the larger pins to a board the heat may damage the crystal.


So... could I solder in a socket instead?

I'll get back to you on that 50 ohm terminator idea.


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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Jan Wed 06, 2021 12:37 am 
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Location: Dallas, TX
You would have to find the right socket for it.
Note that in that ebay ad there are two frequencies listed. They are 10.7 MHz apart, that probably is the IF frequency. However you don't know for sure which frequency is the intended local oscillator frequency, it could be either one. If I were to guess, I would think the 39.75 MHz was the LO frequency. 50.45 MHz sounds like it would be in the HAM 6 meter band.
Do you have a frequency counter to check?
You may be able to rig up some sort of pin clips with short wires to solder to the board.

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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Jan Wed 06, 2021 2:28 am 
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I got a cheap eBay frequency counter somewhere...

What would I need to do?


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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Jan Wed 06, 2021 5:16 pm 
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Location: Dallas, TX
The reason I ask about the frequency counter is that you could confirm the frequency is correct if you use that crystal.
You might be able to make contacts to fit the crystal pin uses contacts from a octal tube socket or similar.
Solder short wires on each contact, then solder the other end of the wires into the board. I would put some heat shrink tubing around the contacts, before you attach them to the board.
The crystal isn't very expensive so give it a try.

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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Jan Wed 06, 2021 9:09 pm 
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Location: St. Louis, MO
Notimetolooz wrote:
The crystal isn't very expensive so give it a try.


Good call. It's only $5 shipped.

I didn't forget about that 50 ohm terminator straight in. Let me put on more clothes and get to it. My workbench is in the basement...


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