General Tech EKG

Being between restorations, I've been collecting and repairing old electronic equipment...like about as old as the TR2! Anyway, I finished an old oscilloscope and found the correct probes to check the TRiumphs EKG. Sorry it doesn't film as good as it looks in person:



I'm (re)learning all the cool stuff you can get off of these, like coil issues, condenser problems, plug condition, mixture between cylinders, and on and on. The coolest thing is this scope was $10k when it was new. I picked it up on a $9 bid on EBay!

Thought it would stimulate some interest?!?

The "blips" from left to right are cylinders 1, 3, 4, and 2 in their firing sequence. The spark is going down...negative...as I am still learning to adapt the scope to a positive ground system. The large blip is the spark firing...preceded by the smaller blip caused by the points opening. The smaller blip after each spark is the points closing and the coil charging back up for the next spark.

Any issues in the primary or secondary ignition is witnessed in the EKG. Each part that doesn't function right will reflect a telltale blip in the EKG. That means no more "guessing" about whether it's the coil, points, wires, cap, plugs, condenser, etc. Each failure has a specific blip. Pretty much anything, except ignition timing.

Well, I thought it was cool for a $9 scope and 2 days with a soldering iron...

When I was in high school taking electronics the teacher had us using oscilloscopes, but the limited knowledge I had faded away. I did met this guy years later that I was working with that wanted to know how to use the equipment and I told him about the teacher and he said that he knew the guy and the teacher was the only guy left that knew anything about it and that he was old, tired, and retired and could not be found. So you are the last man standing with that stuff, very cool!

OK, I'll bite. Here's a picture of my scope with a regular old 10x voltage probe attached to the minus side of the coil, +12v on plus side. I'm using a crane ignition and negative ground. What kind of probe are you using and where is it attached? RPM is 30/t making your idle about 1,000RPM. All I see is the engine speed.

The last couple times my 'old' scope went dead -er actually failed self-diagnostics, was due to failed (shorted) decoupling caps. Sometimes they can be easy to find (visually) -other times a little more difficult. My guess is your scope is decades newer than the TR2/3.

Close, it's a 1965 scope, so older than yours, but only 1 decade newer than the car. I have a nicer, newer scope I'm bringing back to life. Maybe it'll photograph better and I can have a scope diagnosis thread. I am just really floored that these scopes can be picked up for pretty much the cost of shipping, and they are just as relevant today as they were when they were made (40-50 years ago).

Reading off the coil primary can diagnose all the primary issues. Taking it off the secondary adds in all the secondary issues too. This is the probe I bought:

https://m.ebay.com/itm/Hantek-HT25-...-pico-scope-/281320893410?txnId=1719223667018

It's funny they cost more than my scope...but still unbelievable they can make money with free shipping from China?!? China must subsidize all their companies...that's the only way that could be possible.

I got a couple probes, so I use one to trigger on the #1 plug wire. The other pulls the trace off the coil wire. So channel 1 is the trigger and the photo is of channel 2 firing pulses. All I learned for now is the 2 is running great. Now I have to wait for it to act up to try those diagnosis skills from Steve's teacher!

That's very cool!
Several years ago my Dad bought an old Suntune machine at an auction for $10. (one of those big cabinet machines from the late 60s or early 70s.) I don't have the knowledge to really use it to it's full potential, but it's a lot of fun to play around with. The cylinder leak down gauge is even still useful on modern vehicles. I've never attempted to hook the machine up to my positive ground Triumph, it's interesting to know that the ignition pattern reads upside down.

I'm jealous...those Sun Gage's have HUGE readouts! You got a killer deal too.

They used to practically give these old machines away at auctions, but I guess that was 15 years ago now. There's a Suntune on EBay right now that's identical to ours, that the seller is asking over a thousand dollars for! Somehow I doubt he'll be able to sell it. https://www.ebay.com/itm/Sun-Engine-Analyzer/122695965666?hash=item1c913fdbe2%3Ag%3AvqIAAOSwrfVZVVth

Not me, anyway! I drop out after about $25 on old electronics. Restoring this old junk is just like restoring Triumphs...it does take parts, and parts cost money.

Hmm, your scope is older than I thought. I didn't know they started putting values on the screen that early. The ebay description of your probes is almost understandable. 'Techy' speak is difficult when spoken (or written) by someone who actually speaks English, let alone someone who doesn't.

So, if your probe is AC coupled at 100mV/div and the probe is x10,000 your reading a spark voltage of roughly 1,500v peak?

I too may have to get a probe or two. This sort of reminds me of a class I took back when I was trouble shooting PCs as they came off the assembly line. The class used a diskette to cause the system to read a byte from an odd boundary (not an even 16b addressable word memory location). We could see with a scope where the read occurred on the addressable location, but the data would be latched from the higher order byte, instead of the low order byte. Realistically, the exercise showed us how to better use a scope, but was worthless to help troubleshoot computers that might have this particular malfunction since the only way to get the diskette to load the routine to function was if those functions already worked. It's like using a logic analyzer to find an open trace -an ohm meter will work.

To make the reading go up, instead of down, can't you simply 'ground' the probe to the +12v side of the battery? -assuming the car is not touching anything that would earth it to the same point as the scope.

See Jerry, you're already way over my scope skill set! I didn't have a lot of time to play with the scope, as I spent all my time doing the 500 mile fluid changes and all on the TR...and the kids were coming homefrom school. Once the weather cools I'll bring the TR2 out and really learn how to read it. I will, no doubt, have to tap you for some info!

PS...the scope may be newer...the manual dates back to '65.