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#1
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Any oscilloscope experts?
I picked up an old oscilloscope recently and as I was doing some other work on the SVX tonight, I thought I would have a play with it. I understand how to operate the volts/div and secs/div, but I'm a bit fuzzy on the other knobs and buttons.
The only easily accessible wire that carries signal is the front fuel injector on the driver's side. So I stuck a pin through the wire and hooked up the scope. It was my understanding that this wire floats and the ECU pulls the it down to ground in order to pulse the injector. So I expected to see the voltage floating around 12v and dipping down to zero about 6 times a second (at idle rpm). But all I am seeing is a straight 12v line with a little bit of noise. I tried changing the timebase, twiddled all the knobs that I understand, and a couple of the ones I don't. But still couldn't get anything different. I revved the engine to try and get longer pulses. I even tried the other wire on the same injector, just in case, and got the same thing. Any idea what I could be doing wrong? I keep thinking it must be something to do with triggering. Unless I can get the scope to keep each pulse in the same place on the screen then it will be over before I see it? If nobody has any better ideas then I'll for oscilloscope tutorials.
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Subaru ECU and TCU Website 1992 Alcyone SVX Version L 1992 Alcyone SVX Version L 1994 Alcyone SVX S40-II 2004 Subaru Legacy 2.5 SE Sports Tourer 1996 Subaru Legacy 2.2 GX Wagon 1988 Subaru Justy J12 SL-II |
#2
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You could probably the make/model and get the operator's manual.
Barring that, here's the one I like. https://www.cs.tcd.ie/courses/baict/bac/jf/labs/scope/
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[SIGPIC]http://www.subaru-svx.net/forum/image.php?type=sigpic&userid=5569&dateline=1207440 507[/SIGPIC] Naught but by the grace of God "42" Current Stable By Age:'89 Subaru XT6 Silver "Audrey" as in Hepburn '96 SVX LSi #767Brilliant Red "Lil Red" Now on the front burner. Looking for a totalled, but running parts car. |
#3
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Greetings Phil,
Have you established that it is working OK. Will it pick up an induced 50 cycle signal from the mains 230/250 ac supply, i.e. using a simple unshielded wire within a short distance of mains wiring. There are books covering the use of oscilloscopes and possibly something on the net. I will have a quick look. Special regards, Trevor. P.S. Try these ---- http://www.doctronics.co.uk/scope.htm http://www.facstaff.bucknell.edu/mas...pe/Scope1.html http://www.radio-electronics.com/inf...cope-scope.php
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Trevor, New Zealand. As a child, on cold mornings I gladly stood in cowpats to warm my bare feet, but I detest bull$hit! Last edited by Trevor; 03-18-2008 at 06:31 PM. |
#4
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Phil Most of the time I haven't picked up signal it could be for the following reason,
You can do a simple test on a battery or a DC power source and touch the lead trigger wire to see if the scope works correct first. By the way when you get it going its interesting to look at the Knock sensor. Tony
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1995 - SVX 700,000 K Mine, DMS Struts to lift car 2in. Tyres Wrangler Silent Armor 235/70R16, PBR Radiator. 6 speed with DCCD and R180 rer diff, Heavy duty top strut mounts front and rear. Speedo correction box fitted. New stero (gave up on the old one). Back seat removed and 2 spare tyres fitted for desert driving. ECUTune SC sitting in the box for the next SVX. 1992 - SVX 255 K Wife (Want to stay Married so not allowed to fit SC) 1992 - SVX Pearl with black roof race car roll cauge etc ready to race. Ex Tasman Targa car. 1995 - SVX Green low k mint condiation. 1995 - SVX Rally car, ex Matts car. Now to be used on track. 1992 - SVX red & Black being converted to Mid Engine. 1995 - SVX Red 143,000 bit rough. Owned 5 others Subaru back to a 1974 1400 GSR. |
#5
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I was able to pick up the ignition signal in my Legacy... I'll try to help. What's the brand and model? Can you get us a pic of the knobs?
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Disclaimer: The above post is on the internet. |
#6
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Phil I just tried and didn't get it either. I think that my mistake was to assume that the trigger was postive so the other lead was on the earth. I think that is wrong. It got dark so I will try later, it may be that the trigger is a negitive voltage so other lead goes on the postive.
Tony
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1995 - SVX 700,000 K Mine, DMS Struts to lift car 2in. Tyres Wrangler Silent Armor 235/70R16, PBR Radiator. 6 speed with DCCD and R180 rer diff, Heavy duty top strut mounts front and rear. Speedo correction box fitted. New stero (gave up on the old one). Back seat removed and 2 spare tyres fitted for desert driving. ECUTune SC sitting in the box for the next SVX. 1992 - SVX 255 K Wife (Want to stay Married so not allowed to fit SC) 1992 - SVX Pearl with black roof race car roll cauge etc ready to race. Ex Tasman Targa car. 1995 - SVX Green low k mint condiation. 1995 - SVX Rally car, ex Matts car. Now to be used on track. 1992 - SVX red & Black being converted to Mid Engine. 1995 - SVX Red 143,000 bit rough. Owned 5 others Subaru back to a 1974 1400 GSR. |
#7
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Got a reading its the "Y" input on the scope, probe on the black & white injector wire & other lead to earth on car. Then set timing etc.
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1995 - SVX 700,000 K Mine, DMS Struts to lift car 2in. Tyres Wrangler Silent Armor 235/70R16, PBR Radiator. 6 speed with DCCD and R180 rer diff, Heavy duty top strut mounts front and rear. Speedo correction box fitted. New stero (gave up on the old one). Back seat removed and 2 spare tyres fitted for desert driving. ECUTune SC sitting in the box for the next SVX. 1992 - SVX 255 K Wife (Want to stay Married so not allowed to fit SC) 1992 - SVX Pearl with black roof race car roll cauge etc ready to race. Ex Tasman Targa car. 1995 - SVX Green low k mint condiation. 1995 - SVX Rally car, ex Matts car. Now to be used on track. 1992 - SVX red & Black being converted to Mid Engine. 1995 - SVX Red 143,000 bit rough. Owned 5 others Subaru back to a 1974 1400 GSR. |
#8
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does your occiliscope go to 5-10 milliseconds?
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- John ASE certified Master Tech W/ X1 Twin City Fleet repair, St. Paul, MN need work done? Have tools will travel
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#9
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Thanks for the help and advice guys. I think I have it working now.
The scope is a Telequipment D83 made in 1976. I downloaded the manual for it from the "Boat Anchor Manuals" website. Oscilloscope manuals are funny things. One sentence to describe each knob and then pages of schematics showing the inner workings together with the precise specification of every single transistor, resistor, capacitor and other component on the board. I got it to work by grounding the scope to the + terminal of the car battery, setting it for negative triggering and then connecting the probe to the black and white wire like Tony said. When I say probe, I mean a bit of old coax network cable with a crocodile clip soldered to the end. In the first photo, the scope is set to 5 volts/div vertically and 0.1 second/div horizontally. You can see a -12v pulse every 0.2 seconds. That means the injector is pulsing 5 times per second which means the crank is rotating 10 times per second = 600rpm, which sounds about right for idling speed. In the second photo, the timebase is zoomed in to 2 milliseconds/div, showing that each pulse lasted for 3 milliseconds. Success! Time for a beer to celebrate.
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Subaru ECU and TCU Website 1992 Alcyone SVX Version L 1992 Alcyone SVX Version L 1994 Alcyone SVX S40-II 2004 Subaru Legacy 2.5 SE Sports Tourer 1996 Subaru Legacy 2.2 GX Wagon 1988 Subaru Justy J12 SL-II Last edited by b3lha; 03-20-2008 at 05:19 PM. |
#10
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Great work. I think the best thing about scopes is to look at the singal from the various pulse types sensor Knock, Cam & Crank. If the curve is not clean you know the sensor is failing.
I want to build a harness to plug between the car and the engine so I can pick up a number of test points to be able to use the scope more often and pick up problems before the the CE. Tony
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1995 - SVX 700,000 K Mine, DMS Struts to lift car 2in. Tyres Wrangler Silent Armor 235/70R16, PBR Radiator. 6 speed with DCCD and R180 rer diff, Heavy duty top strut mounts front and rear. Speedo correction box fitted. New stero (gave up on the old one). Back seat removed and 2 spare tyres fitted for desert driving. ECUTune SC sitting in the box for the next SVX. 1992 - SVX 255 K Wife (Want to stay Married so not allowed to fit SC) 1992 - SVX Pearl with black roof race car roll cauge etc ready to race. Ex Tasman Targa car. 1995 - SVX Green low k mint condiation. 1995 - SVX Rally car, ex Matts car. Now to be used on track. 1992 - SVX red & Black being converted to Mid Engine. 1995 - SVX Red 143,000 bit rough. Owned 5 others Subaru back to a 1974 1400 GSR. |
#11
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Good one Phil, you are flying.
You should not have to worry about a probe for the measurements you will be involved with. I wish you all the very best with your quite extensive and taxing project. Going to open a home brew right now and will drink to you. Have a happy Easter. Cheers, Trevor.
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Trevor, New Zealand. As a child, on cold mornings I gladly stood in cowpats to warm my bare feet, but I detest bull$hit! |
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