Just started MPP project

[green]

Thanks folks! Starting to understand a tad more each day. Here is the latest image with CH1 on TP1 and CH2 on outer leg of R3. Am able to use 50us and 5v on both channels. Is this still indicative of a problem at U2? Additional note: Rise time switches between 1 - 2 uS, Fall Time stable on 1uS. Max/Min = 914mV & (-)1.4V

Hi multieagle. I'm not seeing the trigger position indicator at the top of the screen. Set channel 1 scale and probe to x1, 5 volts/div. Set channel 2 display and probe to x10 and 50 volts/div Set trigger to edge, normal, ch1,- slope. Looking at the manual sometimes the trigger indicator is there sometimes not. In the manual the indicator is half way across the screen. It seems like you should be able to move it, but I don't see where. My scope, the indicator can move off screen if it isn't centered when switching to shorter times/div.(example 100usec/div to 10usec/div). Reply #64, Ch1 slope change isn't in the center and there isn't a trigger indicator on the screen. I think understanding the trigger might be the answer.

[multieagle]

Thanks folks! Starting to understand a tad more each day. Here is the latest image with CH1 on TP1 and CH2 on outer leg of R3. Am able to use 50us and 5v on both channels. Is this still indicative of a problem at U2? Additional note: Rise time switches between 1 - 2 uS, Fall Time stable on 1uS. Max/Min = 914mV & (-)1.4V

[Chet]

I can pick this up locally for C$150 http://www.amazon.com/Elenco-Oscillo.../dp/B0002EWO3K Is it a decent buy?

Hi multieagle

If this scope is in good working order it is a good buy. But if you can get your existing scope working better you may not need to spend the money for something that you may not use often.

Regards,
Chet

[Chet]

Hi multieagle


Your scope works by collecting thousands of samples during many repetitive cycles of the waveform that you are trying to observe. If your sweep speed is set at 100 us/division then at a 1 MHz sample rate it is collecting 100 samples X ten divisions = 1000 samples each time the sweep is triggered. These are stored in memory and sweeps are processed by software to reconstruct many of these sample periods into a waveform for display.


Expensive oscilloscopes use a similar method but many of them sample at 1 gigahertz or higher rates.


One problem with a slow 1 MHz sample rate is the signal being observed must be very stable in amplitude and voltage triggering points. If not the software processing cannot align the starting points of each sweep. This results in a choppy distorted reproduction of the waveform.


If the waveform is a very stable sinewave or square wave 1 MHz sample rate works quite well and a very clean display is created.


The waveform from the flyback pulse varies some in firing point and amplitude from pulse to pulse and it is a very short narrow event. This changes the triggering points/starting points slightly. This creates some problem for the software to reconstruct good fidelity of the flyback or the receiver signals.


TP1 is the best reference pulse for processing. The best setup is to always have TP1 on channel 1 and trigger on TP1/channel 1. Then view the TP of interest on channel 2.


The video that you made looks like TP1 may not have been triggered correctly. The trigger point (yellow T arrow) should be adjusted to be half way up on the amplitude of pulse from TP1.


The previous screen shot that you posted with the settings from green wasn’t that bad. Try a few more times paying close attention to the triggering level. And try again to get to a faster horizontal sweep speed of 50, 20, 10, or 5 usec.


Regards,
Chet

[green]

Thanks Green. That makes a difference. I might note that I can get nowhere near 1us/DIV.

Hi multieagle. Thanks for trying. My error on the channel 2 scale, should set 50 volts/div with scale and probe at x10. I don't understand the time scale, maybe someone could explain. Be sure the probe is x10 when looking at coil volts.

[multieagle]

Thanks Green. That makes a difference. I might note that I can get nowhere near 1us/DIV.

I shot a short video using your suggested settings. I reversed probes, as I seem only to get a printout for CH1.

Link: http://www.undergrounddetectors.ca/DSC_2781.MOV It may take a while to load.

Data
Peak: 6.05V
Period: 946us
Freq: 1.06KHz
Time Rise: <1.00us
Fall Time: =894us

[multieagle]

Thanks Green. That makes a difference. I might note that I can get nowhere near 1us/DIV.

[green]

U2 is BAD!

Thanks Chet & Green. Wish I could justify a better osilloscope.

Hi multieagle. Still wondering why your scope won't work. I've tried to fix something more than once that didn't need fixing because the scope was on average and not triggered right. It looks like your scope uses averaging. I would like you to try. Channel 1 probe to TP1, 5 volts/div, display x1, probe x1. Channel 2 probe to coil(R3 or R1), 5 volts/div, display x10, probe x10. Trigger on channel 1(going negative). Time base, 1usec/div. Adjust trigger if needed for a stable display on channel 1.

[multieagle]

I can pick this up locally for C$150 http://www.amazon.com/Elenco-Oscillo.../dp/B0002EWO3K Is it a decent buy?

[multieagle]

Hi multieagle

Attached is a pcb layout with output voltages listed for the U2 oscillator that is used for the +5v power supply. If you don't have the voltages listed for D1, D2 and pin 2/C3 of U2 then U2 is probably bad. If you do have the voltages then U3 is probably bad. These voltages are referenced to TP10.

Regards,
Chet

U2 is BAD!

Thanks Chet & Green. Wish I could justify a better osilloscope.

[multieagle]

Hi multieagle


In reference to the information that green found and that you posted for your scope; post a display of TP3 with a faster setting of the horizontal sweep speed to somewhere around 20us or 50us and we can determine how well it will work for viewing the receiver functions.

Regards,
Chet

Re: TP3
I can get a trace at 50us, but it is too small for detail. I tried adjusting windows display resolution (Windows XP old laptop destined for recycling) but did not help. So, other than readout, trace is not much help at higher voltages. If I try to get a larger trace, say 20.0mV (highest setting) the vertical trace disappears off screen. Anything lower, and vertical trace porgressively falls to a straight line. I may be getting interference from the computer.

[Chet]

Hi multieagle

The NE5534 cannot substitute directly in place of an NE5532. It would require a new pcb with an extra socket to accommodate two NE5534s to replace one NE5532.

Regards,
Chet

[Chet]

Hi multieagle

Attached is a pcb layout with output voltages listed for the U2 oscillator that is used for the +5v power supply. If you don't have the voltages listed for D1, D2 and pin 2/C3 of U2 then U2 is probably bad. If you do have the voltages then U3 is probably bad. These voltages are referenced to TP10.

In reference to the information that green found and that you posted for your scope; post a display of TP3 with a faster setting of the horizontal sweep speed to somewhere around 20us or 50us and we can determine how well it will work for viewing the receiver functions.

Regards,
Chet

[multieagle]

Question regarding NE5532
Can U5 NE5532 be replaced with NE5534? I've read that 5532 is dual, and 5534 singular, both used in audio applications. 5534 appears to produce less noise in professional audio systems. Reason for asking? I have several 5534's on hand, but nada 5532.

The 5532 is a dual high--performance low noise
operational amplifier. Compared to most of the standard
operational amplifiers, such as the 1458, it shows better
noise performance, improved output drive capability and
considerably higher small--signal and power bandwidths.
This makes the device especially suitable for application
in high quality and professional audio equipment,
instrumentation and control circuits, and telephone channel
amplifiers. The op amp is internally--compensated for gains
equal to one. If very low noise is of prime importance, it is
recommended that the 5532A version be used which has
guaranteed noise voltage specifications.


NE5534 Description
The 5534 is a single high--performance low noise
operational amplifier. Compared to other operational
amplifiers, such as TL083, they show better noise
performance, improved output drive capability and
considerably higher small--signal and power bandwidths.
This makes the devices especially suitable for application
in high quality and professional audio equipment,
instrumentation and control circuits, and telephone channel
amplifiers.
The op amps are internally--compensated for gain equal
to, or higher than, three. The frequency response can be
optimized with an external compensation capacitor for
various applications (unity gain amplifier, capacitive load,
slew rate, low overshoot, etc.) If very low noise is of prime
importance, it is recommended that the 5534A version be
used which has guaranteed noise specifications

[multieagle]

Hi multieagle


The scope display has low signal levels in millivolts. It should be swinging plus and minus 3-4v.


The voltage at TP3 should be around +0.9v to +1.0v. Measure for +4.75v on pin8 and -4.75v on pin 4 of U5. If they are off by more than 0.25v check the 5v power supply checks in step 1 and 2 of the build procedures.


Your scope has reached its limits on viewing fast pulses. The flyback pulse is 1 to 2 us in width. Your scope samples at 1 MHz which is a 1 us rate. You need at least a 10 MHz sample rate to resolve much fidelity on fast signals. You can still gleam some useful information but TP3 will be choppy and will lack some accuracy.


Does your scope probe have a voltage rating of 600v or higher? If not you could burn out the input circuit of your computer/oscilloscope by connecting to the damping resistor that has 450v present.




Regards,
Chet

I'm getting PIN4: +4.75V PIN8: +0.154
U4 still checks out okay.
TP2=+.031
Step 1: okay
Step 2: failed TP2



Hantek 6022BE has been discontinued, Specs:
Specifications:

Apprently it can sample up to 48MHz

Channels: 2
Bandwidth: 20MHz
Input Impandence: 1MΩ 25pF
Max. Sample rate:48MS/s
Vertical resolution: 8Bit
Gain range: 20mV-5V, 8Steps
DC accuracy: ±3%
Timebase range: 1ns-9000s, 39 Steps
Vertical adjustable: Yes
Input protection: Diode clamping
X-Y: Yes
Trigger Mode: Auto, Normal and Single
Trigger Slope: +/-
Trigger level adjustable: Yes
Trigger Type: Rising edge, falling edge
Trigger Source: CH1, CH2
Sampling selection: Yes
Waveform Display: port/line, waveform average, persistence, intensity
Network: Open/Close
Vertical mode: CH1, CH2, Dual, ADD
Cursor measurement: Yes
Math: FFT, addition, subtraction, multiplication, division.
Cursor: Frequency, Voltage
Dimensions: 205mm (L) x120mm (W) x35mm (H)
Accessories: Software CD, probes, manual, USB cord
Operating systems supported: Windows 7, Windows NT, Windows 2000,Windows XP, Vista

Features:

The unit conforms to the standard USBXITM interface, and can easily insert into a USBXITM housing allowing the user to build up a combination instrument.
USB2.0 interface, no external power source required, easy to use.
Suitable for notebook computers, or product line maintenance.
High performance, 48MS/s real-time sampling, 20MHz Bandwidth.
23 measurement functions, PASS/FAIL Check, be suitable for technical application> Waveform average, persistence, intensity,invert,addition, subtraction, multiplication, division,X-Y plot.
Saves waveform in the following: text file, jpg/bmp graphic file, MS excel/word file. FFT
One computer can connect many DSO, to easily extend channels.