Seeking Electrical Knowledge

[hddennis]

I started this adventure after seeking advice on another thread about my Maxwell's Distributor cap terminal erosion.

https://forums.aaca.org/topic/327664-cure-for-distributor-cap-erosion-sought/

 

EdinMass mentioned he had a coil tester and I found a similar one online. I had to replace the wires and then found out it had an internal vibrator that wasn't working so I tore it apart and cleaned all the points and got it working. Then it still wouldn't work so I replaced the old paper condenser with a modern capacitor I had for my Maxwell distributor. It started buzzing and I was ecstatic as all of this is WAY out of my wheelhouse.

 

My first question is based on the markings of the old condenser .25 MFD 100 VDC and the new capacitor  224J 630V does it seem I've replaced it with a suitable replacement.

 

My second question is how critical is the vibrator to the operation of this tester? I got it to buzz again but it was very dirty especially on the points from being in a moist environment in the past.

 

I'm asking these questions because I used this now supposedly working tester on my Maxwell's coil and 4 spares I have. One wouldn't spark at all. The others including the one I thought was new old stock and am currently running all failed to go past the upper scale marked with a ?.   So now I wonder do I trust the tester or could some of my repairs be causing low readings?

 

Howard Dennis

[TerryB]

Ok, I’ll jump in.  The vibrator is probably acting as the points in the distributor would if the coil was in the car.  You need to have something emulate the points opening and closing to get a spark out of the coil.  I’ll have to do a little research on your capacitor swap to decode the new one.  For sure the 650v rating is sufficient.  Can you post a picture of the replacement capacitor?  The big issue I see is using a coil tester of unknown working condition on coils of unknown working condition.  You would be best served to test a known good or new 6v coil with your box to see how it performs, that way you have a baseline to judge the coil tester performance.  

 

The two rotary switches in the coil tester can get corrosion on them and create weak connections.  Good news is you can open the back as shown in your pics and spray the contacts of them with electrical contact cleaner to improve their operation.  Also, I assume you have a good battery connected to the coil that can supply the 5 amps to thereabouts the coil will need during testing.  Ignition coils are pretty simple devices and seem to last for a very long time, it’s the distributor points and condenser that usually make life difficult.

[hddennis]

Earlier someone posted what I thought was a very helpful post but it has since disappeared?

 

" 224J is a 0.22uf capacitor. 0.25 is no longer a standard value. Sounds OK to me. That is the value you would substitute if it were in a radio or something. The "j" is +-5% tolerance (of capacitance), and the old one would have been +-20% or worse. You are always ok going higher on the working voltage rating. I would have used a 630V one just like you did. " 

Thank You,

Howard Dennis

 

[TerryB]

3 minutes ago, hddennis said:

Earlier someone posted what I thought was a very helpful post but it has since disappeared?

 

" 224J is a 0.22uf capacitor. 0.25 is no longer a standard value. Sounds OK to me. That is the value you would substitute if it were in a radio or something. The "j" is +-5% tolerance (of capacitance), and the old one would have been +-20% or worse. You are always ok going higher on the working voltage rating. I would have used a 630V one just like you did. " 

Thank You,

Howard Dennis

 

Yes, I found that with some research too.  I think there are tubular 0.25uf capacitors out there in the old radio supply world but 0.22 should be close enough.  That type of capacitor I’d was not in use when I was involved with that stuff. Yes I’m getting old!

[hddennis]

TerryB,

 Thanks for taking time to help me. I came to the same conclusion as you and am currently trying to find a new 6 Volt coil.  I do have good fully charged battery. The new capacitor is the orange Chicklet looking thing in my last picture. I soldered brass tabs on them for use in the Maxwell distributor pictured. Wished I hadn't done such a good job as the tabs were a bear to remove to use the capacitor in my tester.

 

I'm waiting for another vibrator in case the one I repaired is part of my problem.

 

While I've got a knowledgeable listener let me ask one more question. I always tested an electrical system by manually breaking the points and seeing if the coil wire passed a nice strong spark. If it did I always moved on to see where else the problem was. These coils I'm working with now passed with flying colors and even ran my Maxwell. This car has given me fits with everything I try to do. Running the same every time I start it has been the problem I'm trying to cure. Could a coil put out a good strong spark randomly and weakly at other times? 

 

Howard Dennis

 

 

 

[TerryB]

Ignition coils are in the class of autotransformers, that is, one coil is wound over top of another.  Like most transformers they normally work with little fuss.  The wires used inside are coated with an enamel paint like material that insulates the wires and prevents shorting between adjacent wires and between the individual coils inside.

 

With coils that are 100 years old it’s possible this enamel coating is breaking down electrically and allowing some loss of efficiency in making a high voltage spark. The high voltage wire on the secondary winding might be arcing slightly inside the coil causing some spark delivery problems especially as the engine rpms increase.  Also, it’s important to keep all external components in the ignition circuit in tip top shape like making sure the points are clean and the electrical connections are secure and clean.  Same goes for the spark plugs, good clean electrodes.  And of course, good clean battery connections including where the battery is grounded to the car.

 

A long answer to a short question!  The automotive coils I have seen fail, not that I did a lot of this work, was usually failure of the oil filled coils to retain oil.  My 1964 Plymouth had issues in high humidity, turned out the old spark plug wires were bad and the coil was cracked and the oil had leaked out.  On the other side, my 1937 Dodge never had a coil issue, I did need to have the points cleaned occasionally for best running as did several old motorcycles that I owned.  

 

Hope me this helps!

Edited June 21, 2019 by TerryB (see edit history)

[TerryB]

Some photos and text from AEA manual I had for sale:

 

[TerryB]

[Bloo]

4 hours ago, hddennis said:

Earlier someone posted what I thought was a very helpful post but it has since disappeared?

 

" 224J is a 0.22uf capacitor. 0.25 is no longer a standard value. Sounds OK to me. That is the value you would substitute if it were in a radio or something. The "j" is +-5% tolerance (of capacitance), and the old one would have been +-20% or worse. You are always ok going higher on the working voltage rating. I would have used a 630V one just like you did. " 

Thank You,

Howard Dennis

 

 

That was me, and I deleted it later when I realized there was an auto radio vibrator in there. Auto radio vibrators in their native setting have a "buffer capacitor", and it's value and condition are fairly critical. They are high voltage capacitors.

 

On the other hand, 0.25@100v sounds like a condenser for a 6 volt car.

 

I thought I understood how this tester worked, but when I realized I didn't, I deleted the post, intending to come back later and figure it out. TerryB seems to have really hit the nail on the head. Best of luck getting it going.

 

Edited June 21, 2019 by Bloo (see edit history)

[hddennis]

51 minutes ago, Bloo said:

 

That was me, and I deleted it later when I realized there was an auto radio vibrator in there. Auto radio vibrators in their native setting have a "buffer capacitor", and it's value and condition are fairly critical. They are high voltage capacitors.

 

On the other hand, 0.25@100v sounds like a condenser for a 6 volt car.

 

I thought I understood how this tester worked, but when I realized I didn't, I deleted the post, intending to come back later and figure it out. TerryB seems to have really hit the nail on the head. Best of luck getting it going.

 

 

Thanks Bloo, I appreciate any help I can get. Would you know anything about these vibrators?  This one is marked OAK TYPE 83 6 Volt  # 249848. I haven't been able to find anything on these numbers online.

 

Howard Dennis

 

[GLong]

I have a couple of those coil testers.  The vibrator's points often get corrosion on them, and do not make a good electric connection.  Use an ohmmeter to test to see if the points in the vibrator are making a good contact with each other.  I found I had to clean the contacts of NOS vibrator points in order to get the vibrator to energize the coil tester.  

 

I found that the coil tester works well, the wider the gap, the better the coil.  

 

Greg

[Bloo]

Quote

Would you know anything about these vibrators? 

 

You might ask over here: https://antiqueradios.com/forums/index.php and see if anyone has a more useful cross reference. You need a thicker skin on that forum than here.

In radios, the use of modern solid state replacement vibrators is controversial. More than you ever wanted to know here: https://antiqueradios.com/forums/viewtopic.php?f=19&t=323198&start=0

 

I have to plead a bit of ignorance on the subject. I understand vibrators were troublesome back in the day, but my own experience has been mostly positive. Generally I just replaced the buffer capacitor before firing it up, and maybe the rectifier tube, and everything was fine. I understand they have rubber inside, and of course points, and people have had to take them apart. Some guy in Australia or New Zealand came up with a method of running one on line/mains voltage in series with a light bulb to clean up the contacts without taking the vibrator apart. I'm not sure where I saw that. It was 220v or 240v mains.

 

My thoughts are, we know it is a 6 volt vibrator. I only see 3 wires going to the socket. The most common vibrators ever were wired like that. Positive ground or negative ground might make a difference. I suspect the wrong polarity would vibrate, but the contacts might be of incorrect metal to last a long time. Dont hold me to that. In any case, the battery leads on your tester probably determine the polarity. I suspect this is a super-common vibrator.

 

More thoughts: The resistors in the lower right are for 12v or 24v operation. The capacitor is new. There isn't anything else. I would try it with some more modern 6v coils and see what you come up with. If it won't work reliably, the vibrator is the only thing left.

 

One more: If you don't have 6v coils, try with a 12v coil and a 12v battery. You might want to check the resistors if you do. Those are 47 ohm resistors. Check with the switch on 6v, so the resistors are known to be out of circuit. the pair in parallel should be 23.5 ohms and the single one 47 ohms. Don't get too upset unless they are approaching 20 percent, and high. They were only 10 percent tolerance when new.

 

One last: What are those numbers on the scale? Are those Kilovolts? If so, I would expect a lot of old cars to score "poor" or worse.

 

EDIT: GLong posted while I was typing. That's good advice.

 

Edited June 22, 2019 by Bloo (see edit history)

[hddennis]

19 minutes ago, GLong said:

I have a couple of those coil testers.  The vibrator's points often get corrosion on them, and do not make a good electric connection.  Use an ohmmeter to test to see if the points in the vibrator are making a good contact with each other.  I found I had to clean the contacts of NOS vibrator points in order to get the vibrator to energize the coil tester.  

 

I found that the coil tester works well, the wider the gap, the better the coil.  

 

Greg

 

Thanks Greg,

As mentioned before this tester had been in a very damp environment and the 2 sets of larger points were so corroded that I thought they were carbon contacts till filing them opened up a shiny spot and I knew then they were metal. How much did you have to clean the NOS vibrator points as I have one coming in the mail. Looks like I may have to open up that one too.

 

Howard Dennis 

[hddennis]

Bloo, thanks for the advice and links I'll check them out.  I really don't know what those numbers represent.

 

Howard Dennis

[Bloo]

I only brought it up because 2 of those resistors (the two in parallel) could affect your results when testing on 12 volts. I don't know about your situation, but I think some of us would have an easier time coming up with a pile of 12v coils to test than a pile of 6v coils.

 

If needed, you can check the resistance of those resistors with a multimeter set to "ohms" (like the free harbor freight one if you happen have one laying around). Ohms might be represented by the Greek Omega symbol on the meter.

 

Yellow=4 purple=7 black="do not multiply" silver="plus or minus 10 percent". The two 47 ohm resistors in parallel should be 23.5 ohms.

 

The resistor by itself should be 47 ohms, but it is only used on the 24 volt range.

 

[hddennis]

12 hours ago, Bloo said:

 

You might ask over here: https://antiqueradios.com/forums/index.php and see if anyone has a more useful cross reference. You need a thicker skin on that forum than here.

 

 

Bloo, I attempted to register here last night and it seemed to work but failed to send me confirmation and now won't let me use my own log-in and says to contact an administrator which is impossible because that requires a log-in ? Catch 22 ?

 

Howard Dennis

[Bloo]

I sent an email to the site administrator. I did not receive a detailed response (maybe the one I received was automated, and the real one is still coming?) Im not sure, but I have the administrator's email address now. I'll send it to you in a P.M.

[hddennis]

Thanks Bloo, I hated to bother you but I spent all morning on that site trying to find a way to contact somebody and it just isn't there.

 

Howard Dennis

Edited June 22, 2019 by hddennis (see edit history)