Professional Dwell - Tachometer Restoration!

Ғылым және технология

Restoration and alignment of a dwell and tachometer test tool. See the tools needed for calibration, and the math is included, so you can do this yourself too! Lot's of hint and tips as always. Grab a snack and your favorite beverage, sit back and enjoy! Click the SHOW MORE tab below for links.
To learn electronics in a very different and effective way, and gain access to Mr Carlson's personal designs and inventions, visit the Mr Carlson's Lab Patreon page here: / mrcarlsonslab
#learnelectronics #Restoration #MrCarlson

Пікірлер: 341

  • @MrCarlsonsLab
    @MrCarlsonsLab2 жыл бұрын

    To learn electronics in a very different and effective way, and gain access to Mr Carlson's personal designs and inventions, visit the Mr Carlson's Lab Patreon page here: www.patreon.com/MrCarlsonsLab

  • @monfrig6959

    @monfrig6959

    2 жыл бұрын

    Love your video's Mr C !!

  • @Daveyk021

    @Daveyk021

    2 жыл бұрын

    V6s and V8s share the same crankshaft but opposite of each other, so v6=3 and v8=4. What about an in-line 6 cylinder, is that divide by 6 or 3?

  • @richardcranium5839

    @richardcranium5839

    2 жыл бұрын

    @@Daveyk021 on a 4 stroke engine it takes 2 revolutions of the crankshaft to fire all the cylinders. the configuration makes no difference. 3 cylinders fire on a 6 cylinder engine per revolution and 4 on an 8 cylinder.

  • @Daveyk021

    @Daveyk021

    2 жыл бұрын

    @@richardcranium5839 Thank you. Also the distributor runs off the crank. I think this morning, I was in lala land thinking the cam shaft. Since a V engine has two, I was thinking that would change the math. I thinker on cars and small engines (when I have time). I need to check the math to test a TAC and DWELL meter I have (it is digital, so it is probably dead nuts on??). I still like the idea of an analog meter for it. I think that is better to watch the needle swing. I may get on ebay and order and old analog tac/dwell meter before they are all over $1000 after too much of the public see this video.

  • @mdrew44628

    @mdrew44628

    2 жыл бұрын

    @@Daveyk021 V engines can also have only one camshaft. They were the older engines that had pushrods and lifters. The camshaft was in the block right over the crankshaft.

  • @blobscott
    @blobscott2 жыл бұрын

    For those wondering why 'dwell' matters in old cars with breaker point ignitions: The dwell angle is the number of degrees of crankshaft rotation in which the points are closed. During this period, the magnetic field in the primary winding of the ignition coil is building. When the points open, the magnetic field collapses quickly generating a brief high voltage, which is stepped up even more in the secondary coil eventually arcing across the spark plug gap. The longer the dwell angle (i.e. points closed), the more time there is to build a magnetic field in the primary - an increase in this magnetic fields leads to a higher voltage at breakdown and a better spark. The dwell angle is set by adjusting the breaker point gap - i.e. how far apart the points are when they're pushed open by the cam lobe. A larger gap implies a smaller dwell (inverse relationship) because the breaker points in the small dwell case are adjusted such that they open sooner on the cam lobe and are ultimately pushed farther apart at the top of the lobe. Because breaker points can be pitted due to arcing, adjusting the points gap distance (with feeler gauges) is relatively inaccurate (as the points faces may not be flat) and having a dwell meter does a much better job at getting a proper adjustment. Incidentally, I believe vintage race cars occasionally used dual point systems (and possibly additional coils ?) to maximize coil charging at high rpms - a scheme where every other ignition cycle would take place on the alternate coil/points set that would be fully charging during the previous cycle. I may have the details of this last part wrong. Anyway, I hope this is interesting/helpful to someone out there :-)

  • @MrCarlsonsLab

    @MrCarlsonsLab

    2 жыл бұрын

    Very well said!

  • @Discretesignals

    @Discretesignals

    2 жыл бұрын

    The ignition dwell angle isn't derived from crankshaft rotation. It's is derived from distributor rotation. Crank rotates twice the speed of the cam. For example a 4 banger has breaker lobes that are 90 degrees apart, so the dwell angle would be around 45 degrees.

  • @andrew_koala2974

    @andrew_koala2974

    2 жыл бұрын

    blobscot It is not actually a secondary winding in the coil. It is an overwind -- much as the overwind in LOPT [Line Output Transformers Transformer] used in devices employing a CRT Other than this small error in your description, all is accurate

  • @dak682

    @dak682

    2 жыл бұрын

    @@MrCarlsonsLab No points in todays cars ???

  • @MrGeoffHilton

    @MrGeoffHilton

    2 жыл бұрын

    Thanks for the explanation because I was wondering about dwell angle!

  • @joelima201
    @joelima20110 ай бұрын

    Just finished fixing up a Canadian made Tuffy Tool model 1813 Tach-Dwell meter , thanks to this video. Having access to a function generator was able to calibrate rpm and dwell accurately. Was out by a bit due to out of tolerance resistors , linearity is perfect across the whole span of the meter. I use this for my Canadian ' 66 Malibu SS . Still running points as the car still has its original 283. Great Job Paul !

  • @marcossouza4872
    @marcossouza48722 жыл бұрын

    I wonder how can someone dislike a video with this level of knowlege and care. Congrats, Mr. Carlson. Your content and you are simply awesome.

  • @mdrew44628

    @mdrew44628

    2 жыл бұрын

    Trolls...every channel has them....🙂

  • @andrew_koala2974

    @andrew_koala2974

    2 жыл бұрын

    Marcos Souza Those that dislike the video presentation are likely those who have little to no knowledge on the subject matter, and perhaps have the attention span of a house-fly. One cannot teach those who choose to live a life of ignorance. The tragedy is that they take pride in their ignorance.

  • @marcossouza4872

    @marcossouza4872

    2 жыл бұрын

    @@andrew_koala2974 I think you got it spot on. I don't have the hands-on knowledge on the subject-matters Mr. Carlson shows us (very little practice, I only got the theoretical electromagnetism part of it), but I admire the simplicity and practicality he demonstrates in every video. Also, I really appreciate the old and new equipment he shows and restores (we never saw 99% of those brands and products in Brazil).

  • @cobrasvt347

    @cobrasvt347

    2 жыл бұрын

    Jealous trolls that will never amount to anything is how dislikes happen. They have nothing better to do but what they do best. Troll

  • @n7565j
    @n7565j2 жыл бұрын

    My father had a tach/dwell meter, (which is still (probably) in his garage ;-), that he used to make fine adjustments to the points on his 69 Imperial. They used to call me "Mic Eye" when I was younger cause I could adjust the points without a feeler gauge. (I couldn't really tell the gap, but I had done it so much that I could get it REALLY close, so close that dad rarely had to adjust them once I'd set them) Thanks for the trip back in time Mr Carlson!!! I sure do miss my dad!!!

  • @MrCarlsonsLab

    @MrCarlsonsLab

    2 жыл бұрын

    Thanks for sharing your story Brian!

  • @bobsbarnworkshop7542
    @bobsbarnworkshop75422 жыл бұрын

    My lifetime career was in electronics! 3 years at Westinghouse, 18 at Kodak and 12 at Rochester Institute of Technology! Loved my life’s work! Over those years I collected dumpster dive test instruments bound for the recycler! Most need repairs!! Want to fix them! Ha ha! Thanks for the videos!

  • @MrCarlsonsLab

    @MrCarlsonsLab

    2 жыл бұрын

    Glad you enjoyed Bob!

  • @bobsbarnworkshop7542

    @bobsbarnworkshop7542

    2 жыл бұрын

    @@MrCarlsonsLab I have a 67 Mustang and 72 VW beetle and I still have my old Dixco tach/dwell meter to adjust ignition timing! Now I know how to calibrate it! THX! I’m also restoring a C64 and disc drive, fixing some old cb radios and building cb antennas! I’ve been retired 8 years but I try to learn something new every day! Thanks for that!!!

  • @jeffclark2725
    @jeffclark27252 жыл бұрын

    Wow ,I haven't opened a Sears Dwell meter , I didn't realize how much adjustment was avalible,Great video,

  • @BixbyConsequence
    @BixbyConsequence2 жыл бұрын

    I think the last time I used one of these was probably 1983 and yes, it was from Sears! That and the stroboscopic timing light. Fun times.

  • @KD2HJP
    @KD2HJP2 жыл бұрын

    My old man taught me this, on a Craftsman in the late 70's early 80's..He's missed. Thanks for this

  • @MrCarlsonsLab

    @MrCarlsonsLab

    2 жыл бұрын

    Glad you enjoyed Charles!

  • @RussMcClay
    @RussMcClay2 жыл бұрын

    I love Mr Carlson's Lab!

  • @nickbarret9368
    @nickbarret93682 жыл бұрын

    FYI, one would use a dwell meter while cranking the engine, usually with plugs remove, and set the gap while watching the meter. This also avoids getting oil on the point faces since you are not using feelers. Nice vid man

  • @can-cruiser
    @can-cruiser Жыл бұрын

    I just calibrated a somewhat similar unit to the one in the video (a hand held style) that was also sold by Sears (Made in Japan). It could only read up to ~1000 RPM on the V8 scale even at the highest setting of the calibration potentiometer. I opened it and found a single electrolytic capacitor (47uF/10V) which is laughable since the unit normally run in a 12V-14V environment. I replaced the capacitor with a 47uf/50V and it worked beautifully and calibrated accurately throughout the whole range. Thought of sharing this for anyone who may contemplate such calibration.

  • @bradleyleben7785
    @bradleyleben77852 жыл бұрын

    When I started doing mechanic work over 50 years ago that was the tool to have to get your car is running great. I really enjoyed this video. It’s because of videos like this that I became a patron sometime ago. The only thing I can use my old dwell tachometer on is the tractor.🤣👍 I look forward to all your videos. Keep safe Paul.

  • @MrCarlsonsLab

    @MrCarlsonsLab

    2 жыл бұрын

    Thanks 👍

  • @andrew_koala2974

    @andrew_koala2974

    2 жыл бұрын

    Bradley Leben Becoming a patron was an excellent decision. There is always something one can learn, irrespective of age or experience.

  • @howardhiggins9641
    @howardhiggins96412 жыл бұрын

    Thanks for the video. Sears tune up equipment was always very accurate OoB. I owned several over the years. In the 60's, the name they were sold under was Penske, as in Penske Racing Working on small sports cars, the most important readings were usually for low idle speeds. High speeds were not used as much, except for maybe checking your tachometer. The dwell meter was especially useful as that was the function that indicated the quality of your distributor bearings and points-springs. I was kind of hoping you were going to have to build in some calibration controls if this didn't have any originally. Please set aside some time in the future, to do one of those too. Thanks again.

  • @wayneparris3439
    @wayneparris34392 жыл бұрын

    Knowing that you have moved the labs all around, it feels a little funny to see the old main lab in the intro and outro! Sears always had major manufacturers make their house brand devices. It is possible that the design really is a SUN product though it really does not matter. Nice job as is your normal! Even my "old" truck (1973) has electronic ignition so the dwell function to me is not needed. So many people today look down on the old way to do things. A needle is much easier to use when doing things like setting RPM as it is the way our brain works, analog not digital. Great job on a device I had totally forgotten about! NOW TO THE UFO device!!! :D

  • @JamesLCoxe
    @JamesLCoxe2 жыл бұрын

    This is unique, always surprised by how your acumen in electronics applies to so many different fields.

  • @MrCarlsonsLab

    @MrCarlsonsLab

    2 жыл бұрын

    Thanks for your kind comment Jim!

  • @emehlhar
    @emehlhar10 ай бұрын

    This video was on the mark as I just purchased an almost identical Sears meter with an additional range for voltage. The meter needs calibrating so your video was just the help I needed. Thanks so much Mr Carlson.

  • @hailmynova
    @hailmynova2 жыл бұрын

    That is the cleanest dwell meter I've ever seen in my life lol didn't know it can go out of spec sitting in a box.

  • @aodhmacraynall8932
    @aodhmacraynall89322 жыл бұрын

    Ive been looking for how to do this for ages. I have 2 of these. One is accurate and the other not and I didn't know how to fix it. I'm impressed with how easy this is to do. Thanks.

  • @MrCarlsonsLab

    @MrCarlsonsLab

    2 жыл бұрын

    You are welcome!

  • @keithcoltron3171
    @keithcoltron31712 жыл бұрын

    Impressed is somewhat miss-understated, I really did not expect this 'Pro'! meter to be anywhere near as accurate, (so much is labelled 'Pro' now days and it means crap really) hats off to the designer and manufacturer, they really came up with something quite special, obviously the meter movement is of quite high quality not something you would get today unless you pay 'think of a number and double it' price, the old school stuff wins again, thanks very much for showing this Paul it was VERY interesting to watch and see it truly shine at the end!

  • @MrCarlsonsLab

    @MrCarlsonsLab

    2 жыл бұрын

    Thanks for your kind comment Keith, and taking the time to write too!

  • @electropuff6098
    @electropuff60982 жыл бұрын

    I like restoration of old Devices in your lab

  • @MrCarlsonsLab

    @MrCarlsonsLab

    2 жыл бұрын

    Thanks!

  • @micametalgem3721
    @micametalgem37212 жыл бұрын

    Speaking of Sears Roebuck and Co, some decades ago you could buy from them model T spark coils. We bought one as kids to use for making a Tesla coil. That was around 70 years ago.

  • @jwashington
    @jwashington2 жыл бұрын

    This brought me back to the 80s watching the technician calibrate our Allen Test scope. Great explanation.

  • @richardcranium5839
    @richardcranium58392 жыл бұрын

    love the video but i might suggest that a brief description of how the circuit converts hz to meter movement for rpm and duty cycle is converted for dwell

  • @Piltdownpaul
    @Piltdownpaul2 жыл бұрын

    Being a car mechanic , its been a very very long time i checked ther dwell angle on a vehicle, ahh the good old days.....

  • @W1RMD
    @W1RMD2 жыл бұрын

    I was going to congratulate you on 300k subscribers last week and didn't get around to it. So, congratulations on 301k subscribers! Thanks for your great videos!

  • @gregorythomas333
    @gregorythomas3332 жыл бұрын

    You have to remember that this meter was made during a time when Sears cared about making products well instead of today's habit of making things cheap and customers having to come back to replace it much quicker.

  • @MrCarlsonsLab

    @MrCarlsonsLab

    2 жыл бұрын

    Absolutely!

  • @andrew_koala2974

    @andrew_koala2974

    2 жыл бұрын

    Gregory Thomas The CORPORATE Empire which now controls and operates a de facto Government with its BS HQ in Pennsylvania Avenue in the District of Corruption - You may have heard reference to it as DC -- The Currency you work for goes Directly there. They are connected to SkyNet and have their hands in your pockets and have made your employer to act as their collection agent. You may be a GT but you cannot outrun DC Good luck and goodbye

  • @samanthafox8273

    @samanthafox8273

    2 жыл бұрын

    I'm sure that 'Sears' as it existed back in the day, still cares about good products. The problem is that all the people and ethics associated with Sears as it used to be have retired, been pushed out or otherwise replaced with sociopathic greed-mongering hyper-capitalists. It might be money that's the problem, or perhaps it's just unethical folks that just want to use us all to make a quick buck. In many ways life in 2021 is of a much higher quality than in 1960, but our money buys so very little now. I was born in 1990 and even I've seen a drastic down-turn in my 31 years, in the quality of products. We have to bring back more stringent product quality regulations and penalize outsourced production, while incentivizing local production sources.

  • @can-cruiser
    @can-cruiser2 жыл бұрын

    Great video. Thanks.. The wedge shaped PCB is probably because the same board was used in a hand-held device variety of the same meter. Just a guess..

  • @MrCarlsonsLab

    @MrCarlsonsLab

    2 жыл бұрын

    You're probably right!

  • @cobrasvt347
    @cobrasvt3472 жыл бұрын

    I rebuilt my serious exhaust gas analyzer and got It working flawlessly once again

  • @radio-ged4626
    @radio-ged46262 жыл бұрын

    Learned a few things on this video. Strangely not about electronics but motors!

  • @egomezmx65
    @egomezmx652 жыл бұрын

    There is no "big thumbs icon" so I will let you know in write I REALLY ENJOY YOUR VIDEOS !!!! thanks a lot for taking the time with this great, educational and quality produced videos!!!

  • @MrCarlsonsLab

    @MrCarlsonsLab

    2 жыл бұрын

    Thanks for your kind words Edgar!

  • @gregorymccoy6797
    @gregorymccoy67972 жыл бұрын

    This is all new to me and I've driven lots of old cars. I'm off to a new video to fill that gap. Need to learn about dwell. I never fail to learn something new from these videos.

  • @MrCarlsonsLab

    @MrCarlsonsLab

    2 жыл бұрын

    Glad it was helpful!

  • @gyrgrls
    @gyrgrls2 жыл бұрын

    Thanks for sharing. These were used on the old Kettering ignition system. I once got in an argument with the guy at my local tune-up shop. I told him I was looking for a canned answer. He said: you mean "condenser"? No. a canned answer. It's a condenser. But that's beside the points. Let's not dwell on it, OK? I got the canned answer I wanted.

  • @joed2392
    @joed23922 жыл бұрын

    Hi Paul. You have just made lot's of shade-tree mechanic's and hometown racing team's Very Happy !!!

  • @MikeDilworth-ne1my
    @MikeDilworth-ne1my Жыл бұрын

    Thanks Paul! Got out my old ArcherKit Engine Analyzer to check the calibration and sure enough it was off! That kit had you do the CAL of the tach using a line cord with a few 56K resistors in series with the Hot and Neutral. You plug it in the wall socket and attach your test leads to the ends of the resistors to get 60Hz (ish) line frequency. Got you close, thanks for the video and math to check the other RPMs!

  • @MrCarlsonsLab

    @MrCarlsonsLab

    Жыл бұрын

    Glad it helped Mike!

  • @BrendaEM
    @BrendaEM2 жыл бұрын

    It might be interesting to also have the complimentary video: How to Tune an Engine with an Oscilloscope. : )

  • @hiflyer1825
    @hiflyer18252 жыл бұрын

    with these d'arsonval needles I also check needle balance {weight at end of needle}. This is done in horizontal and vertical position of meter to check that 'zero' position doesn't change. AAAHHHH memories.

  • @PaulinesPastimes
    @PaulinesPastimes2 жыл бұрын

    Excellent. I have a Dwell/Tach meter that is much cheaper than this lovely thing and have used it since the 90s. Now I need a function generator to test it! There's always something 😄

  • @n4nln
    @n4nln2 жыл бұрын

    This is like apprenticing to Gandalf. All the old knowledge, spells, but most importantly, wisdom. You cannot buy this anywhere.

  • @FranksModelAviationWorkshop
    @FranksModelAviationWorkshop Жыл бұрын

    Great video! I just bought a vintage Snap-on tach-dwell meter. It needs re-wired, but your video will definitely help if I need to adjust it. Thanks for sharing.

  • @MrCarlsonsLab

    @MrCarlsonsLab

    Жыл бұрын

    Glad to help Frank!

  • @kevinmccool3719
    @kevinmccool37192 жыл бұрын

    How ironic that you did this video as I just recently found a really nice Sears unit in someone's trash that does all these tests plus it has all the plug in test cables with it. Unit is in great shape. I'll probably never use it other than maybe the voltmeter and ampmeter. Looks good for the bench though. Also got a near mint complete old g.e. beige plastic portable record player. Can't wait to check it out.

  • @VitoVeccia

    @VitoVeccia

    2 жыл бұрын

    It has other uses believe it or not. It can be used to retrieve codes from OBDI Ford's, and it can be used to place a load test on circuits. Before condemning a purge solenoid, you can put the meter in its place, and it load tests the circuit so that you don't need to do voltage drop tests.

  • @DonDegidio
    @DonDegidio2 жыл бұрын

    Hi Paul, Had the same unit. Saw less use when the HEI distributors started making an appearance. Don't know where my unit is now. I sold my shop when I retired in 2018 and closed down my trucking company. Enjoyed the video. You and the family stay safe. 73 WJ3U

  • @blackarrow8683
    @blackarrow86832 жыл бұрын

    So sad the old lab is gone. All the great memories 😢

  • @MrCarlsonsLab

    @MrCarlsonsLab

    2 жыл бұрын

    It's just going to get better :^)

  • @samanthafox8273
    @samanthafox82732 жыл бұрын

    I'll be honest, as much as I love older motors and older electro-mechanical systems, this stuff is why I'd much prefer to drive a vehicle with an electronic ignition haha. Great tutorial though, I'm sure this will come in handy due to my fetish for old automobiles!

  • @zappatx
    @zappatx2 жыл бұрын

    Good timing! I use my old Sears unit (later model than this one) but just bought a Heathkit Automotive Scope to test the dwell accuracy thus calibrate - I should have just waited for this video!!

  • @samvoelkel2046
    @samvoelkel20462 жыл бұрын

    This video is a very nice contribution to the automotive world; it will be a resource for decades. Thanks.

  • @hadireg
    @hadireg2 жыл бұрын

    I learned smth new again 😊👍 TY Paul!

  • @macchina1969
    @macchina19692 жыл бұрын

    Another fantastic video - very good idea with the second cam for the function-generator! I like your extreme accuracy on the alignment procedures :-) 73s Ernst

  • @johnparichuk8367
    @johnparichuk83672 жыл бұрын

    I can understand your skepticism working on a Sears branded piece of equipment. It works the opposite way, also. 25 years ago, my cousin handed me a top of the line Carver receiver to repair. I was excited to get my hands on it. It turns out, the receiver was actually made by Pioneer, which was a bit of a let down. I did get it repaired and back to my cousin.

  • @dhpbear2

    @dhpbear2

    2 жыл бұрын

    "Is that a REAL poncho or a SEARS poncho" - Frank Zappa :)

  • @peteshulver9221
    @peteshulver92212 жыл бұрын

    Yet another great video and Paul your knowledge knows no bounds !!

  • @MrCarlsonsLab

    @MrCarlsonsLab

    2 жыл бұрын

    Thanks 👍

  • @IanScottJohnston
    @IanScottJohnston2 жыл бұрын

    Back in the day we used to buy open frame 1mA movements from Farnell (IIRC), and they'd arrive in all sorts of states!.....requiring spindle adjustment top and bottom to keep the coil level as well as adjusting the freeness of the movement. Yes, it was an art to get it all adjusted perfectly and linear.

  • @Theoobovril
    @Theoobovril2 жыл бұрын

    Very interesting and a very good video, Paul; much enjoyed.

  • @MrCarlsonsLab

    @MrCarlsonsLab

    2 жыл бұрын

    Glad you enjoyed it!

  • @Timothycan
    @Timothycan2 жыл бұрын

    Hi Paul. Many years ago now, I used to be employed as supervisor of a small group of calibrators of mechanical meters. The device should really be calibrated and used in the same way, that is, if it is to be used standing up, it should be calibrated so, or if used lying on its back, then calibrate it in that position. With a good meter, any difference should be very small, but nevertheless when we issued a calibration certificate it would only guarantee the stated accuracy if used the same way it was calibrated.

  • @geraldstewart

    @geraldstewart

    2 жыл бұрын

    You need to adjust the meter movement so it works right in all positions

  • @Timothycan

    @Timothycan

    2 жыл бұрын

    @@geraldstewart very few mechanical meters will give precisely the same reading in ALL positions. Hence, a tolerance is given, and the instrument is tested in only the positions it is expected to be used. For example, a mechanical AVO meter could be calibrated both vertically and laid on its back. If then used on its side for example, it could be outside tolerance.

  • @TeslaTales59
    @TeslaTales592 жыл бұрын

    Nice job. Good to stray out of radios and such. Maybe work on a cool old timing light next?

  • @welderfixer
    @welderfixer2 жыл бұрын

    Paul, As smart as you are I have to wonder if there is anyone that you look up to. Before I get any older I'd better start your electronics classes very soon! Thank you a thousand times over!

  • @hahaahah7214
    @hahaahah72142 жыл бұрын

    Always excited to watch another video of you!

  • @Bigolg1975
    @Bigolg19752 жыл бұрын

    Great video, thanks for sharing!

  • @TheRadioShop
    @TheRadioShop2 жыл бұрын

    Had one in the early 80's with the wedge shaped circuit board. It was also a Sears but was a hand held unit. The circuit board was in the handle and the top was a meter. Looks like when they made that model you had they could not be bothered making up a new board for it. Great video as always Paul.

  • @MrCarlsonsLab

    @MrCarlsonsLab

    2 жыл бұрын

    Thanks for stopping by Buddy!

  • @metalbill
    @metalbill2 жыл бұрын

    I have an old, different Sears Tach-Dwell meter too. I think I'll be doing this now. Thank You!

  • @MrCarlsonsLab

    @MrCarlsonsLab

    2 жыл бұрын

    Glad it helped Bill.

  • @jessstuart7495
    @jessstuart74952 жыл бұрын

    On a 4-stroke engine, each cylinder fires every 720°. The ignition system fires every 720°/(# of cylinders); Let's call this the "firing angle". A 4-cylinder has a firing angle of 180°, a 6-cylinder has a firing angle of 120°, and an 8-cylinder has a firing angle of 90°. The dwell angle is the rotational angle of the distributor the points are closed and the coil is storing up energy (magnetic flux) for the next spark. The tricky thing to remember, is that the distributor (and cam shaft) spins at 1/2 the speed of the crankshaft. The voltage on the coil's low terminal is small (near ground) during the dwell time because the points connect the low side of the coil to ground, or ground through a low valued resistor. For calibrating a Dwell Meter with a pulsed signal of variable duty cycle, the dwell angle is the fraction of the distributor rotation angle where the waveform is "low" (near 0V). Distributor Rotation Angle = 1/2 Crankshaft Rotation Angle Dwell Angle = (1/2)*(Firing angle)*(1-Duty_Cycle) For the 6-cylinder case with a 50% duty cycle, the Expected Dwell Angle displayed on the meter would be Dwell Angle = (1/2)*(120°)*(1-0.5) = (60°)*(0.5) = 30° It's not 50*(0.6) gets you the same answer, but I think you switched the decimal points around on the two numbers. I thought your viewers might appreciate a more detailed explanation. The dwell angle can be controlled by adjusting the "points gap". Side Note: PWM methods (frequency to voltage conversion, and duty cycle measurements) generally have excellent linearity.

  • @Zonfeair
    @Zonfeair2 жыл бұрын

    Sigh what memories this brings back. I used several analog meters back in the day for both tach dwell and electrical service in the automotive industry from 1970's to 1990. Now that I am getting into electronics I am sad I sold them in a yard sale and only have digital meters now.

  • @nathkrupa3463
    @nathkrupa34632 жыл бұрын

    You Or Genius Sir Very Detail Explain & nice Video Sir.

  • @RGB06084
    @RGB060842 жыл бұрын

    Thanks Paul for what you do here and on Patreon!

  • @MrCarlsonsLab

    @MrCarlsonsLab

    2 жыл бұрын

    You're very welcome Robert!

  • @preiter20
    @preiter202 жыл бұрын

    All of the timing on my race car is done in the ignition box. My Dad and brother have a race pak in their car and we can change the timing during the run. I do have a dwell meter and a timing light in the garage in a box. I should dig in out and give it a go through. Congratulations on 300K Paul!!

  • @andrewsmactips
    @andrewsmactips2 жыл бұрын

    I have a Hawk hand held dwell tach meter and the casing is exactly the same shape as that circuit board so, mystery solved.

  • @andymouse

    @andymouse

    2 жыл бұрын

    Nice catch !....cheers.

  • @alelsenaar

    @alelsenaar

    2 жыл бұрын

    I was just going to post the same.

  • @geraldstewart

    @geraldstewart

    2 жыл бұрын

    Now we know who made it for Sears

  • @jj74qformerlyjailbreak3
    @jj74qformerlyjailbreak32 жыл бұрын

    I’d love to have a dwell. Great video.

  • @deaconblue949
    @deaconblue9492 жыл бұрын

    I had a Sears VOM back in the early eighties and it was a pretty good meter. Not Simpson quality but plenty good for general use. I don't know if it's still spot on anymore but I'm not surprised your meter came back around with a little tlc.

  • @joeteejoetee

    @joeteejoetee

    2 жыл бұрын

    Very nice avatar Deacon Blue! I love my Simpson too. BTW: My SG membership card labels me as a "Healer of Appliances". Bravo!

  • @robertthegrape2192
    @robertthegrape21922 жыл бұрын

    Great video! Once again I learned a lot from your videos. Thanks, Mr. Carlson!

  • @MrCarlsonsLab

    @MrCarlsonsLab

    2 жыл бұрын

    Thanks for the feedback Robert!

  • @JohnnyUmphress
    @JohnnyUmphress2 жыл бұрын

    The reason for the wedge shaped circuit board? My guess is that the manufacturer used the same board for the handheld model where the board is mounted in the handle with the meter movement above it.

  • @MrCarlsonsLab

    @MrCarlsonsLab

    2 жыл бұрын

    You are probably correct.

  • @danielmelendrez1616
    @danielmelendrez16162 жыл бұрын

    Congrats on the 300k! Very much deserved. Best electronics channel in "KZread town"

  • @MrCarlsonsLab

    @MrCarlsonsLab

    2 жыл бұрын

    Thanks Daniel!

  • @peternewman958
    @peternewman9582 жыл бұрын

    The tapered PCB is probably the same as used in the meters that had a tapered handle with meter display at the top.

  • @davidminderman3179
    @davidminderman31792 жыл бұрын

    In the day, I always wanted one. Now I have one for my 68 Karmann Ghia, Now that I know; I should align it. Thank you!

  • @MrCarlsonsLab

    @MrCarlsonsLab

    2 жыл бұрын

    Glad it helped David!

  • @wilco3588
    @wilco35882 жыл бұрын

    It has a thin angular circuit board because the same circuit board was used in a smaller handheld version that the circuitry was in the handle and above it was the meter gauge.

  • @Scorpio722
    @Scorpio7222 жыл бұрын

    Great little video on the tach/dwell. Now please straighten the meter ( grin. )

  • @jp040759
    @jp0407592 жыл бұрын

    Great topic. I have a vintage SUN dwell/tach meter and I just didn't feel like digging in the math to figure out how to simulate pulse train that will simulate engine RPMs or dwell timing. It is pristine except for some slight surface scuff in the paint. Internally it is totally clean. Not sign of any battery corrosion at all ever

  • @aleastwood1698
    @aleastwood16982 жыл бұрын

    I liked this Vid I Have a Sears Tack/Dwell meter it is a dual meter it also has a ohm/volts meter

  • @kenabi
    @kenabi2 жыл бұрын

    that subtle sears shade.

  • @a.c.t.solutionsinc8024
    @a.c.t.solutionsinc80242 жыл бұрын

    VGG would approve your Vice Grip use. (Hear's "hyup.... ahhh.... well I just dont even understaaannndd....hyuh...git on outta therrre" while Mr C slowly turns the nut off)

  • @ke4est
    @ke4est2 жыл бұрын

    Excellent Video as always! Glad to see you are getting things close, so you can start making videos on restorations!

  • @shieldcracker
    @shieldcracker2 жыл бұрын

    Excellent video! I am really looking forward to the analog instrument movement.

  • @GeorgeWMays
    @GeorgeWMays2 жыл бұрын

    Super fun. Thanks Mr. C. It is appreciated.

  • @alpcns
    @alpcns2 жыл бұрын

    Thanks mr. Carlson. Interesting as always. That studio mike is a gem, excellent sound quality too. I'd love to see the electronics of that.

  • @aodhmacraynall8932
    @aodhmacraynall89322 жыл бұрын

    Very interesting video.

  • @wktodd
    @wktodd2 жыл бұрын

    Wedge shape: probably a board from a hand-held model.

  • @throttlebottle5906

    @throttlebottle5906

    2 жыл бұрын

    or it allowed more circuit boards condensed into same physical size board. rotate every other circuit layout 180 degrees, then angle cut between them. :)

  • @mackfisher4487
    @mackfisher44872 жыл бұрын

    Sir you are a man of many talents.

  • @DavidTipton101
    @DavidTipton1012 жыл бұрын

    Nice job again Paul, I have a quite large Dwell/Tacho meter in the cupboard for the last probably 30 years since last use, I might drag it out for a play. Someone might be able to use it, thanks 🙂

  • @MrCarlsonsLab

    @MrCarlsonsLab

    2 жыл бұрын

    Glad you enjoyed Dave!

  • @chrisyoung3082
    @chrisyoung30822 жыл бұрын

    Always learn so much from your vids ....thanks again !!!

  • @ronniebrown8775
    @ronniebrown87752 жыл бұрын

    Really a great educational video Mr C. on this type gear! I have a lot of Snap On electronic gear from my fathers garage that could use an alinement and refurbishment!

  • @MrCarlsonsLab

    @MrCarlsonsLab

    2 жыл бұрын

    Glad it was helpful!

  • @pookatim
    @pookatim2 жыл бұрын

    In the old service station I worked in back in the day, we had a big "SUN" cart with several types of portable meters you could select. The only one I ever saw any mechanic use was the Tach/Dwell meter. I was well worn while all the others looked brand new. It took a lot of punishment. No idea how accurate it actually was. LOL!

  • @bones007able
    @bones007able2 жыл бұрын

    Ahh the good ole days , when a fella could tune up his engine himself .... those days are long gone

  • @darkgreen68
    @darkgreen682 жыл бұрын

    IS THIS REALLY FAIR! for a old school car guy this is like hiding peas in mashed potato's. twisting electronics with automotive, I love your videos this one made me think of all the times working on cars with a meter like that.

  • @davidarnette327
    @davidarnette3272 жыл бұрын

    That was a good one. Haven't seen one of those in years. Keep up the good work

  • @nnnvp
    @nnnvp2 жыл бұрын

    Hi Mr C! Good job 👍

  • @MrCarlsonsLab

    @MrCarlsonsLab

    2 жыл бұрын

    Hey, thanks!

  • @AceMon2005
    @AceMon20052 жыл бұрын

    I had a good feeling that it would align well as soon as I seen the extruded aluminum case, Japan made meter, and brass nut holding the selector knob on. Nowadays I would expect to see an all plastic case, China made meter, and pot metal fasteners. Keep up the great work.

  • @ronvi4539
    @ronvi45392 жыл бұрын

    really enjoyed this video...

  • @MrCarlsonsLab

    @MrCarlsonsLab

    2 жыл бұрын

    Glad you enjoyed it Ron!

  • @robincross4625
    @robincross46252 жыл бұрын

    You always impress me. There are times I laugh. You are a very good technician. As a retired Broadcast Engineer who cut my teeth on valve technology, I feel that you are a little bit excessive on the safety of high voltage circuits. It is still better to be safe. On transmitters we ALWAYS did several things. Remove all jewelry. Keep one hand in a pocket. Us the shorting stick to verify the power supply is discharged. Good work! Excellent audio! As always, nice production.

  • @DaleDix

    @DaleDix

    2 жыл бұрын

    The main thing here is that he has to be careful about safety warnings because he doesn't want to get into trouble if someone does something silly.

  • @andrew_koala2974

    @andrew_koala2974

    2 жыл бұрын

    Robin Cross Exactly. When I was studying Electronics Engineering and Electro-Mechanical Engineering. (during my 30-year long Military career - Airforce) - The practical side of things was done with PHILIPS who were building the avionics systems for our U.S. built fighter jets. My then Mentor suffered a cardiac arrest when the metal bracelet on his watch attracted an arc from an EHT lead that had been punctured by an unknown technician -- presumably to measure the EHT voltage. I learned from his experience and never wore a watch or a ring after that. Besides keeping one hand 'in pocket' It also pays to stand on a rubber mat. Rubber car mats are under $6 and a potential lifesaver. I had the opportunity years ago. mid-1990s to visit a sign manufacturing business, where they were making NEON signs - and one of their benches was a salvaged Stainless Steel bench presumably from a commercial kitchen or Butcher - I was horrified when I checked it to discover it was not earthed. - Suffice to say that the shop proprietor is Lebanese. Perhaps he obtained the table from a Lebanese bakery.

  • @codefeenix
    @codefeenix2 жыл бұрын

    awesome!

  • @bobvines00
    @bobvines002 жыл бұрын

    Paul, I look forward to learning from your adapter for this dwell/tach meter for it to work with 6V vehicles. Please show enough detail so that I can adopt _that_ to an 8V vehicle (i.e., a 6V Willys that starts a _whole_ lot better on 8V than it does on its original 6V! ;). I've got an "old" Sears dwell/tach test tool that I purchased in the mid-'70s that I'm sure needs a similar calibration like you've shown here.

  • @MrCarlsonsLab

    @MrCarlsonsLab

    2 жыл бұрын

    Will do Bob. Should be an easy circuit.

  • @billgates3699
    @billgates3699 Жыл бұрын

    Yo Carlson This video involves all my interests. Automotive and electronics. But hey, logarithmic needles call for logarithmic scales 😂 The easiest way to fix this whole issue is to print a more accurate scale and just glue it under the needle. Not kidding.

  • @roncooke2188
    @roncooke21882 жыл бұрын

    Great video interesting

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