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I’ve seen several posts herehere and here suggesting that adding a diode to the clock can prevent sparking and reduce wear on the contact points. I gave it a try, but I’m still seeing a spark—maybe a bit fainter, but it’s hard to tell for sure. Shouldn’t the diode eliminate the spark entirely? Is it possible I did something wrong?
I bought a 1N4004-TP from DigiKey.com and installed it as pictured below:
Here is evidence of a bright green spark. I also clearly saw the spark in a pitch black room but was unable to capture it on video.
hope you find this helpful - but its hard to tell exactly from your photographs, but it appears that you may have installed the diode in parallel to the existing magnet wire, which would render it useless. look carefully at this photo for a correctly installed diode.
Ron '66 roadster
I’ve seen several posts herehere and here suggesting that adding a diode to the clock can prevent sparking and reduce wear on the contact points. I gave it a try, but I’m still seeing a spark—maybe a bit fainter, but it’s hard to tell for sure. Shouldn’t the diode eliminate the spark entirely? Is it possible I did something wrong?
I bought a 1N4004-TP from DigiKey.com and installed it as pictured below:
Here is evidence of a bright green spark. I also clearly saw the spark in a pitch black room but was unable to capture it on video.
Pretty certain that a diode acts to only keep current flowing in one direction and not in the other direction - like a check valve allows fluid flow in only one direction. Since the clock works to wind the main spring based on applying voltage to an electric solenoid, which is a coil of wire that becomes an electric magnetic when voltage is applied, and is therefor is an inductive circuit, placing a properly sized capacitor in parallel with the contacts would act to absorb the “flash” (capacitors store voltage) and in that way prolong the life of the contacts. What size capacitor to use? I don’t know, but I’m thinking some additional research would yield a capacitance value that would work. Others of course can comment.
Not familiar with this mod, so I may be talking out my a$$. But a capacitor seems to be what you need. Just like the "condenser" on your ignition points.
The coil is an inductor. When the current through an inductor is shut off, the field generated by the inductor collapses and generates a high voltage referred to as back EMF, flyback effect, inductive kickback, etc...... Placing a diode across the coil, with the cathode to the positive side, will form a simple snubber or clamp that will limit the back emf to the forward voltage of the diode. I don't believe this is what you are seeing and what the diode would help with.
As mentioned, a capacitor across the contacts would help absorb the spark you see, value probably 0.1uf, but I have to question whether this is really necessary. A good cleaning, burnishing, of the contacts and it should be good to go for another 60 years.
This is another thread <https://www.corvetteforum.com/forums/c1-and-c2-corvettes/4323249-body-off-resto-official-start-date-today-12.html>
Originally from plaidsid. https://www.corvetteforum.com/forums...ransistor.html
Might be helpfull.
Cheers, John
Last edited by gsorange; May 26, 2025 at 01:43 PM.
Reason: Added orignal source
You will still get a small spark after installing the diode. It is significantly less intense than no diode. I have three movements I have converted and one in my car now. (Yes I am a redundant pack rat). I made a YouTube video and posted it on CF a few years back. Looks like you have installed the diode correctly.
here is a pic of one of my movements I pulled out of my stash.
hope you find this helpful - but its hard to tell exactly from your photographs, but it appears that you may have installed the diode in parallel to the existing magnet wire, which would render it useless. look carefully at this photo for a correctly installed diode.
Ron '66 roadster
This is the exact picture I used to guide me, I think I did it the way it is illustrated in the picture.
This is commonly done on relays and solenoids that are connected to "chips" because the Back EMF will destroy the chip in short order and this lets it go to ground instead. But what is really being protected here? It seems to me that the BEMF is still being generated across the contacts, and now it just has someplace else to go.
Erosion of the points in the clock. It helps to eliminate metal transfer. This is the same erosion that happens to the points in the ignition. However the capacitor in the ignition system helps to absorb the voltage surge. Cleaning and filing down the points in the clock is not as easy as the ignition points. The points in the clock do not seem to be as robust as the ignition points. This is just my opinion.
Here are some pics of a couple well worn out points.
Last edited by smacota1; May 28, 2025 at 01:52 PM.
Erosion of the points in the clock. It helps to eliminate metal transfer. This is the same erosion that happens to the points in the ignition. However the capacitor in the ignition system helps to absorb the voltage surge. Cleaning and filing down the points in the clock is not as easy as the ignition points. The points in the clock do not seem to be as robust as the ignition points. This is just my opinion.
Here are some pics of a couple well worn out points.
Regarding the robustness of the clock points - I removed two point contacts from new ignition points, removed the point contacts in the clock, and then soldered the two point contacts from the ignition points back into the clock. Really wasn’t that hard to do at all. Worked great.
This article is from a very old "Skinned Knuckles" magazine and I used this to do my 64 clock.
Originally Posted by gsorange
This is another thread <https://www.corvetteforum.com/forums/c1-and-c2-corvettes/4323249-body-off-resto-official-start-date-today-12.html>
Originally from plaidside. https://www.corvetteforum.com/forums...ransistor.html
Might be helpfull.
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Clock Diode Help
