oscilloscope patterns, gauging interest

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sandt38

wheelchair class racer
Jun 20, 2012
#1
Our machines are really fairly simple, but in some cases it would be nice to lay to rest the "is it my CDI?", "my stator?", etc. topics.

As a professional wrench with 25 years of diagnosis I have found one of the most valuable tools I have is my oscilloscope. A scope basically displays a photographic representation of electrical amplitude (voltage or peak voltage) over a period of time (frequency). Today scopes can be had on the cheap, and they can make quick work of figuring out why our machines are not functioning.

A buddy of mine had a Scrambler and his bike just quit running. His diagnosis by the manual left him questioning weather he needed a CDI or stator or ignition switch or... "Replace with a known good part" is a junk diagnosis, and it can be quite costly and time consuming. The manual was also wrong.

I brought my DVOM (no cheap meter, either it is a Fluke 87) and followed the manual. It stated the stator needed to display 33 volts peak DC current. It then stated to unplug the stator and read across the 2 wires. As a diagnostician I knew that you tested AC voltage generators this way and a DC voltage would require a voltage input which would not occur with the stator unplugged. I also knew that a stator does deliver an AC voltage. The manual also wanted me to test the pickup trigger the same way, with an expected voltage of 3.5 VDC.

In testing as the manual stated the DVOM showed 1.9VDC peak on the stator and ~0VDC on the pickup. So what did it need?

My scope showed a cranking AC voltage of 34 volts, with a clean AC signal at the stator and .9 volts (albeit a clean pattern) at the pickup. The manual stated a gap adjustment of ~.020" of the pickup relative to the flywheel... I told him I thought the adjustment was wrong. We tore it down and low and behold, the gap was ~.250. He had broken his backup pullcord starter and tied it together about 3 months ago. The knot had apparently jammed in between the pickup and the flywheel, knocking it out of adjustment. Resetting the adjustment (and cleaning up his knot) fixed the issue.

A simple $100 scope could have saved him $290 on the CDI and over $400 on the stator/pickup assy (they come as a "kit).

So, who would be interested in seeing details on how to set up a scope, analyze what you are seeing, and photographs of important testing, with known good patterns? I am planning on scoping my bike and storing the patterns (my scope costs a tiny bit more then $100 ), and frankly I will not need to photograph or write up anything on my testing, but I will take the time to help those of you interested if enough people want to see such a tutorial. I can also help analyze anomalies in the patterns you post up, if any questions are raised. If the interest is nominal I will not spend the time doing all this.
 

hoser

Active Member
Apr 11, 2012
#2
Great topic. I would be interested in seeing some of your findings. Troubleshooting and diagnosis can be two of the most difficult parts of fixing a machine, especially when it is electrical. I would appreciate any information you can post.
 

OTMTRX

Active Member
Apr 9, 2012
#5
Top idea Sand.. Thanks for doing it (if ya do).. I use these things called "DataQ modules" (I'm sure there are plenty of similar products out there too) in work for capturing intermittent bad signals etc, they are just a little box you connect to a laptop or PC via usb and they capture/store waveforms. They really are pretty trick, via the s/w you can set up how they measure etc.. I think they are under $50 for the basic version (which is all you'd need for a bike/car).. I'll dig into it a bit more and see if I can get a low cost kit worked out.. I know scopes can be had pretty cheap but most of those don't have a true capture function..
 

CJM

Truck Yea
Jan 5, 2013
#6
Excellent idea! I have access to such tools but as a middle of the road B tech I generally dont do electrical diagnosis and generally never have. Wish I knew more electrical.
 

sandt38

wheelchair class racer
Jun 20, 2012
#7
I am an AC Delco Master tech, former ASE Master with L1 (haven't needed them in years so they lapsed) tech.

My Verus (scope, scanner, information system). I'll be pulling and capturing with this unit.



My Maxidas and Verus:



I think I may go ahead and do this. I'll yank the diagrams this weekend and pull the captures this coming week. Hopefully I'll have it done by next weekend.
 

sandt38

wheelchair class racer
Jun 20, 2012
#9
Very nice setup, that stuff is NOT cheap!
The Maxidas is actually quite affordable. They retail for ~$2,000. I got mine a hell of a lot cheaper, as a tool guy wanted me to go to a few shops and demo them for him. It has extensive coverage (I can do Bugattis for crying out loud, but I actually do a lot of work for the local Lotus club, and it does not have Lotus coverage), tons of bi-directional control, Chrysler SKIM/SKREEM and Ford PATS programming, but the graphing is worthless. Honestly, and I have used a lot of scanners, I think it is definitely the best value.

The Verus, on the other hand, is more expensive than almost every manufacturer scan tool. With my accessories (scope and scanner), Flash programmer, and the full European package, I have ~$15,000 into that device. $10K for the base package, $2K for the European, and the coverage is not as good as the Maxidas.
 

CJM

Truck Yea
Jan 5, 2013
#10
Wonder if the modis or solus would do the same? Thats all I can nab off the shop I used to work for, that or the mac mentor iirc. Chances are I got some sorta old engine analyzer laying about that would work or I can find one to borrow.

I got out of shop work and drive a battery service truck for AAA (contractor) these days, WAY easy work vs slaving in the shop and it works with my school schedle better.

Seriously interested in what you come up with tho.
 

sandt38

wheelchair class racer
Jun 20, 2012
#11
Wonder if the modis or solus would do the same? Thats all I can nab off the shop I used to work for, that or the mac mentor iirc. Chances are I got some sorta old engine analyzer laying about that would work or I can find one to borrow.

I got out of shop work and drive a battery service truck for AAA (contractor) these days, WAY easy work vs slaving in the shop and it works with my school schedle better.

Seriously interested in what you come up with tho.
Yes, the Modis does have a scope (your set-up on that will be the exact same as what I will be using in the tutorial), no the Solus does not it is just a scanner. The Mentor (same as the OTC Genesis) has an external scope module that has to be purchased and installed, but frankly it is a real piece of shit scope.
 

hoser

Active Member
Apr 11, 2012
#13
The thread you started is already starting to look like it will be VERY informative and helpful. Looking forward to seeing the rest of your posts.

As long as we are talking about scan tools, I have a Snap On Ethos. I know, it is basically worthless for anything other than pulling codes and watching simple parameters. But I would like to have it updated. I have heard that I have to pay for every update between the one that is currently on my scanner and the latest one. Is this true? It seems like that would cost me more than a new scanner with the current software on it already.
 

sandt38

wheelchair class racer
Jun 20, 2012
#14
The thread you started is already starting to look like it will be VERY informative and helpful. Looking forward to seeing the rest of your posts.

As long as we are talking about scan tools, I have a Snap On Ethos. I know, it is basically worthless for anything other than pulling codes and watching simple parameters. But I would like to have it updated. I have heard that I have to pay for every update between the one that is currently on my scanner and the latest one. Is this true? It seems like that would cost me more than a new scanner with the current software on it already.
No, you can just get the current update. SnapOn offers loyalty discounts if you up it every year (for example, my Verus updates are $1200 a year, but if I update every year by October I pay $900) but there is no need to update every year.

Now, I know that the Ethos underwent some changes a few years back, and I believe some of the older units cannot be updated. I am honestly not sure of the specifics on that, you will have to talk to your SnapOn rep, but I just wanted to forewarn you.