Author Topic: SNAP-ON Automotive Oscilloscope MT 665 (Read 20518 times)

Paul Moir · « **Reply #50 on:** March 27, 2017, 05:45:26 am »

These are integral to Ted's Dynamometer's operation, aren't they? I always wanted to be one of those guys in the lab coats.

What was going on with the horizontal? Anything exciting?

james_s · « **Reply #51 on:** March 27, 2017, 07:45:56 am »

Well, I fix stuff like this now and then because it's fun to fix stuff, and it's a neat gadget regardless of how useful it actually is. I'm sure it is of some use at least on cars of a particular era. I suspect the reason so few of them actually get used is largely that the average automotive technician has no clue how to use one or what to do with the information it gives them.

jcrubin · « **Reply #52 on:** March 28, 2017, 02:21:53 am »

Quote from: Paul Moir on March 27, 2017, 05:45:26 am

These are integral to Ted's Dynamometer's operation, aren't they? I always wanted to be one of those guys in the lab coats.

What was going on with the horizontal? Anything exciting?

I had that hotwheels suitcase set with the handle when i was a kid.....

In the previous week id found that an accidental application of the probe to the IC caused a deflection and confirmed that the horizontal was handled on that separate board. I was looking at the circuitry and couldn't figure out why all of this effort went into the weird timing they used for it but since i knew that board was the culprit, I brought it home. I started checking all of the components but the 741 caught my eye, having messed with several on the IT-1121 project, I decided to swap them out with that one and check the known V/H values from my heathkit. Sure enough The output pin was reading positive input voltage.

When I got the board back into the unit i checked the supplied voltages of +24 and -8, which sounds kinda strange but they come right off the low voltage DC power supply and i confirmed it, so I popped in a new 741 and it lit right up.

The project isnt over and several things still require repair. However on primary parade we were able to hook it to a car where a known worn cam lobe was known to exist and expressed itself as predicted on the crt. Both primary and secondary parade have a test signal for exact RPM's from a signal off the coil. RPM's that send a signal to .... yup... the horizontal driver board to align all of the cylinders for testing, we can fake it for now but the other components will need to be repaired. The videos for all this will start releasing in one month.

james_s · « **Reply #53 on:** March 28, 2017, 05:11:20 pm »

What does the scope actually connect to? How does it tell you a cam lobe is worn? Now I'm curious to know more about this thing, I had assumed it just measured ignition timing or something.

jcrubin · « **Reply #54 on:** March 28, 2017, 05:49:08 pm »

Ill admit that the application of the device is a bit foreign on some of these tests. Its not like there are any in operation. Jason has been trained on them and works on older cars and specializes in air-cooled engines such as VW. Luckily we have the original Manual so ill be able to retrieve it and provide information on the tests. I may steal it this weekend. Towards the end of all this obviously the movies will migrate from repair to calibration to operation.

Id be interested to see how my old shovelhead looks on the device, which can be dialed down to 2 cylinder operation so it will also work with motorcycles

jcrubin · « **Reply #55 on:** April 01, 2017, 10:43:27 pm »

Yeah, so more issues, Secondary raster and parade produces no signal, it never ends.......... not the worst place ive been with this thing. Could just be a bad clamp on the cable or another 741... ANYWAY as promised!!!!!!!

Though, im not at the point where I can casually go through the whole book yet, i made it my business to find this section and snap a photo

jcrubin · « **Reply #56 on:** April 24, 2017, 01:03:32 pm »

The first of the movie postings start to go online this week, and while the project is not completed, still having logical issues, its still far enough along to have content.

jcrubin · « **Reply #57 on:** May 01, 2017, 12:27:28 pm »

The second movie in the series is now available.

jcrubin · « **Reply #58 on:** May 15, 2017, 12:42:44 pm »

jcrubin · « **Reply #59 on:** May 29, 2017, 06:07:30 pm »

Video 4 posted

jcrubin · « **Reply #60 on:** June 19, 2017, 03:33:38 pm »

Muxr · « **Reply #61 on:** June 19, 2017, 11:32:47 pm »

+1 for vintage gear. Thanks for sharing, and nice repair

texaspyro · « **Reply #62 on:** June 20, 2017, 03:37:31 am »

If you look at the data sheets for high voltage rectifiers, many of them have different max voltage ratings for unpotted and potted usage. I have some rated at 3KV unpotted and 20 KV potted.

Also, when building high voltage circuits don't leave any sharp edges sticking out of the wiring (like cut component leads). They are sources of corona discharge and arcing. Make sure the joints are fully embedded in a smooth solder blob.

And ideally you should vacuum process the potting. Air bubbles are a no-no. It's really hard to get a proper bubble-free mix with standard epoxies... even with a vacuum. One thing that helps is to add a few drops of thin silicone oil to the mix... I use silicone oil used in model race car shock absorbers.

jcrubin · « **Reply #63 on:** June 20, 2017, 05:34:36 pm »

Video 6 posted

jcrubin · « **Reply #64 on:** June 26, 2017, 01:10:26 pm »

Video 7 posted

jcrubin · « **Reply #65 on:** July 03, 2017, 01:00:42 pm »

Video 8 posted

https://youtu.be/ahTyNg3xj1U

jcrubin · « **Reply #66 on:** July 10, 2017, 01:03:01 pm »

Video 9 posted - the end

texaspyro · « **Reply #67 on:** July 10, 2017, 03:14:06 pm »

You can parallel two 1 ohm resistors to get 0.5 ohms. So to fix your low ohm cal, just parallel one of those one ohm resistors with another one ohm resistor.

jcrubin · « **Reply #68 on:** September 09, 2017, 01:17:18 pm »

Recent movie on the buggy work shows the MT665 in full operation

KArnold · « **Reply #69 on:** November 15, 2017, 02:57:13 am »

I need advice regarding my MT665. We work specifically on antique cars, mostly air cooled Franklins. The scope would be a big help. With the scope on, and the engine not running, I only see a dot on the screen. I can adjust the the dot vertically with the the vertical position adjustment. I cannot expand the dot horizontally to form a line. I can move the dot off the screen to the right with either the horizontal position or horizontal expand controls. I can move it back on the screen about 1/3 of the way from the RH side of the CRT - no further.

I removed the Horizontal card and cleaned the plug and contacts with electrical cleaner. This made no difference in the above results. With the scope hooked up and the engine running I have a vertical line which appears to be be made up of more than one spike (like a very tight secondary pattern). What is the possibility that this could just be the Horizontal card, and if so, would one of you be willing to look at it?

Thank you ,
Kirk Arnold
kirka9152@aol.com

james_s · « **Reply #70 on:** November 15, 2017, 08:35:50 pm »

It's obvious that either the horizontal deflection amp is not working or the horizontal oscillator is not oscillating. Why this is I can't say but it's probably something fairly simple.

jcrubin · « **Reply #71 on:** November 16, 2017, 04:06:42 am »

Not to say it would be the same issue, but in my case it was the failed OPamp as shown in that movie for horizontal troubleshooting,


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Author Topic: SNAP-ON Automotive Oscilloscope MT 665 (Read 20518 times)

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