(Topic ID: 257246)

Classic Stern 16B-6 Transformer Restoration


By ita47

44 days ago



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  • 48 posts
  • 9 Pinsiders participating
  • Latest reply 6 days ago by pinballinreno
  • Topic is favorited by 9 Pinsiders

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#1 44 days ago

Here are pictures of the transformer I got with my Stern Nine Ball. As you can see someone has done a number to this thing. I don’t see any broken wires so I think it maybe ok other than the one bakelight plastic being broken in half and the paper torn up. I am looking for ideas on how I can replace / repair the plastic and paper? I plan to completely restore my Nine Ball and I don’t want the transformer to look like this. Has anyone ever restored a transformer that can offer some suggestions?
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#2 44 days ago

Those usually have varnished "Kraft" paper.

Maybe you could use a sheet of fishpaper instead?

#3 43 days ago

Is there a way to get the fishpaper or kraft paper through the metal sections? The original paper almost feels like it has a wax coating on it.

#4 38 days ago

Does anyone have pictures of the front and back of a Stern 16B-6 Transformer? The front of mine is mostly there but the back is missing. I am going to try to reproduce the paper wrapping. I have a Meteor with the same transformer but it is on location 40 miles from me right now. I would appreciate the help.

#5 32 days ago

Today I decided to hook power up to this thing and check the voltages. It is wired for 115v but I have 120+v input so that may have played into the numbers I got. But I decided I will change it to 120v when I rewire it if it works. Here are the voltages I got:

Terminals 8 & 10 = 193.3 volts AC

Terminals 2 & 6 = 54.6 volts AC

Terminals 17 & 18 = 7.71 volts AC

Terminals 13 & 14 = 8.85 volts AC

Terminals 15 & 16 = 13.85 volts AC

Do these voltages sound right with nothing connected to the transformer other than power?

3 weeks later
#6 11 days ago

I reproduced the wrapper for the transformer tonight. The font is not exactly the same as the original, but pretty close. I also found some heavy weight brown paper I think will match pretty good. I also bought and assembled a new Weebly rectifier board and I got a new power supply wire harness from Third Coast Pinball I will be installing.

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#7 8 days ago

Today I painted the transformer core. I used a satin black, and I think it looks a lot better. Next step is to disassemble the core and repair and replace the wrappings on the windings. I also plan to make a stencil to repaint the 16B-6 on top.

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#8 8 days ago

It was time to disassemble the core plates so I could fix the damage and replace the wrapper. The first step is to drive out the wooden wedge, being careful not to damage anything.

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#9 8 days ago

Once the wooden wedge is out you can begin removing the plates. Take your time and go slow. I used an xacto knife to seperate the plates. Some were stuck pretty good so be careful not to cut yourself. I was also very careful to keep the plates in the order I took them out. I simply stacked them as I removed them so I could put them back in the same order they came out.
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#10 8 days ago

It took about 45 minutes to remove the plates, but I was trying to be careful and keep it all organized. Once all the plates were removed I could assess the damage which thank goodness was mostly cosmetic. I removed the old outer wrapper and any other loose tape.
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#11 8 days ago

Next I mixed up some two part 5 min epoxy and worked it in under the broken bakelite strip. I then wrapped the entire thing in 3M strapping tape. The tape held the bakelite strip in place while the epoxy dried too. I then took the new wrapper I made turned it over and sprayed it with 3M Super 77 spray adhesive. I let it set a couple of min and then positioned it on the windings.

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#12 8 days ago

I let the glue dry a few min and then started putting the core plates back in. I started at the top of my stack and reinstalled the plates in the reverse order that I took them out. I had to use a small dead blow hammer to tap the last 2-3 in place.

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#13 8 days ago

When reassembling your core plates note that they should be isolated electrically from one another but bonded together. There is a specialized transformer dip lacquer that is used during manufacturing that is usually heat cured. Following is a note from an electronics forum relating to rebuilding old transformers:

The individual laminations have to be electrically isolated from each other (otherwise, the core could be just a big chunk of silicon steel). They are usually assembled with the lacquer as a temporary "glue" to hold them in their place. They are electrically isolated to keep eddy currents as small in circular cross area as possible (to keep heat buildup in the core low). The lacquer "glue" also keeps the core from vibrating at the energized frequency to keep it quiet.

#14 8 days ago

I then put some temporary bolts in to hold everything together. I sat it up on the bench and used my dead blow hammer to tap all the plates back flat. First on the top, then on the side. Once the plates were realigned it was time to put the wooden wedge back in. I slowly tapped it in place with with my dead blow hammer. I got a paint stick and cut it down and used it to drive the wooden wedge back down inside.
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#15 8 days ago

Really curious to see if the transformer works after this.

#16 8 days ago
Quoted from minnesota13:

When reassembling your core plates note that they should be isolated electrically from one another but bonded together. There is a specialized transformer dip lacquer that is used during manufacturing that is usually heat cured. Following is a note from an electronics forum relating to rebuilding old transformers:
The individual laminations have to be electrically isolated from each other (otherwise, the core could be just a big chunk of silicon steel). They are usually assembled with the lacquer as a temporary "glue" to hold them in their place. They are electrically isolated to keep eddy currents as small in circular cross area as possible (to keep heat buildup in the core low). The lacquer "glue" also keeps the core from vibrating at the energized frequency to keep it quiet.

Thanks for the tip, I wasn't aware of that step. I just read the thread you quoted from and there seem to be mixed opinions if each plate was coated or the whole thing was dipped after being bolted together. I know the coating keeps the core from vibrating but I don't know anything about the eddy currents. I will say the plates were only lightly stuck together on this transformer mainly around the edges. I would think if each plate was coated before assembly they would have been very hard to separate. I honestly don't know you maybe right each plate may need to be coated. I would also think since I didn't do anything to the plates other than separate them, if there was a coating on each plate it would still be present on one of the two plates that touch.

If I need to take it apart and coat the plates I can, it's just time. You mentioned coating them with Lacquer and polyurethane was also mentioned in that thread. I would think either would work.

Here is the link to the full thread if anyone wants to read it.
https://forum.allaboutcircuits.com/threads/what-is-the-clear-plastic-coating-i-see-on-laminations-of-electrical-transformers.134030/

#18 8 days ago

I have just now stumbled onto your excellent post. I'm probably way too late for your needs but I have a 16B-6 I can posts pictures of if your still need them.

#19 8 days ago
Quoted from cottonm4:

I have just now stumbled onto your excellent post. I'm probably way too late for your needs but I have a 16B-6 I can posts pictures of if your still need them.

Does your tranformer have any readable text above and below the 16B-6 part number? I could see on mine it had some text but it was unreadable. Also feel free to post some pictures of yours for comparison.

#20 8 days ago
Quoted from ita47:

Does your tranformer have any readable text above and below the 16B-6 part number? I could see on mine it had some text but it was unreadable. Also feel free to post some pictures of yours for comparison.

OK. give me a couple of days.

#21 7 days ago

Put some line voltage AC on transformer pins 1 and 9 (yellow and red wire stubs) and see if it works OK or has a loud hum. It it has a noticeable hum under no load it will be louder under load.

The original insulating finish to the core plates may be good - it looks like an oxide finish. But if the plates are not bonded together you will get vibration hum that you may be able to resolve with external thin lacquer application. You will may want to coat your new paper wrap as well.

#22 7 days ago
Quoted from minnesota13:

Put some line voltage AC on transformer pins 1 and 9 (yellow and red wire stubs) and see if it works OK or has a loud hum. It it has a noticeable hum under no load it will be louder under load.
The original insulating finish to the core plates may be good - it looks like an oxide finish. But if the plates are not bonded together you will get vibration hum that you may be able to resolve with external thin lacquer application. You will may want to coat your new paper wrap as well.

What type of Lacquer should I use? I have been searching the web but haven't found much. The one pinballnreno referenced comes in a 2oz. bottle and is red.

#23 7 days ago

Lacquer is difficult to find, fumes are not healthy. If I had this project, I would use off the shelf clear varnish. I would thin the varnish to water like consistency to help it wick between any openings between the plates and brush it on.

#24 7 days ago
Quoted from ita47:

What type of Lacquer should I use? I have been searching the web but haven't found much. The one pinballnreno referenced comes in a 2oz. bottle and is red.

I know that manufacturers of guitar pickups dip their windings in some sort of wax. Beyond that, I have no idea. I do know that bee's wax has a high melting point. So it might work for an electronic dip. Don't know if it would contain or stop any stray voltage. But liquid bee's wax would flow into every crack and crevice.

Here is something I found on making guitar pickups. Will it apply to making transformers? I don't know, but this might give some useful info.

https://www.instructables.com/id/Make-A-Guitar-Pickup/

Potting or saturating a pickup with wax is done to help keep the wires in the coil in place and prevent the pickup from becoming microphonic.

I used Gulf Wax (candle wax) to saturate my pickup because it was available, but you could also use a mixture of 80% candle wax and 20% beeswax.

Melting the wax directly on top of a heat source, in a saucepan on the stove, for example, can overheat the wax and cause it to become highly flammable. And we do not want to lose our eyebrows while making guitar pickups do we? NO! So, to melt the wax, I filled a big container about half full of almost boiling water and placed a smaller container inside. A tin can works transfers the heat from the water to the wax more effectively, so use one if you have one handy. Gulf wax comes in blocks, which don't melt very quickly, so I used a knife to break the wax into smaller pieces. Then I put this wax in the smaller container.

When the wax is completely melted, hold your pickup by the lead wires and submerse it in the wax. You will see bubbles coming out of the coil and you need to leave the pickup in the wax until the bubbles stop. For me this seemed to be about 5-10 minutes, but for you it could be longer.

Take the pickup out of the wax and wipe of the excess while it's still in a liquid form.

#25 7 days ago

I hooked the transformer up last night and powered it up. It does vibrate a little. I do think the plates need to be "glued" together with varnish to help prevent this. I will have to decide if I should take them apart to coat them or just coat the plates as a stack and hope I can get some in between the plates. Most of the vibration is coming from the outer edges.

I do have some Lenmar UltraLaq in stock. It is a precatalyzed lacquer finish. I think this will work fine and may give it a go.
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#26 7 days ago

I'm an electrician and I'm watching this with keen interest. You may have just raised the bar in terms of the things that people have to do in a full restoration. Bless you and curse you!

#27 7 days ago

Well this whole experiment may or may not work, have to wait and see when I'm finished. I felt like I had nothing to loose but time, so why not give it a try. My options were simple, try to fix this mess of a transformer or search and buy a replacement (which isn't that easy to find). I appreciate all the comments and suggestions, I am definitely no expert, I just thought I would share the experience. Before I began I searched the internet trying to find someone that had restored a pinball transformer but couldn't find anything. If this ends up working then maybe this thread will help someone else, if it doesn't work they will know what not to do. I should find out pretty soon if it is going to be a success or total waste of time.

#28 7 days ago
Quoted from ita47:

I also plan to make a stencil to repaint the 16B-6 on top.

I think the factory used rubber stamps and not stencils to ID these. I check into getting a rubber stamp made and was quoted around $15.00 which is not bad for a rubber stamp. But the ink was killer priced. I'm still thinking on it.

The pic is not of mine but I do have transformer marked with the manufacturer name stamped on like the one you see here. The maker was Ravenswood Electronics in a town called Ravenswood near/in near Chicago. The Chicago pinsiders might be able to shed light on the town of Ravenswood.

Anyway, the transformer in this pic plus one I have are the only two I have seen with the Ravenswood name stamped on. I have no idea how many were tattooed like this. When I get around to marking mine I will probably include the name along with the number.

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#29 7 days ago
Quoted from cottonm4:

I think the factory used rubber stamps and not stencils to ID these. I check into getting a rubber stamp made and was quoted around $15.00 which is not bad for a rubber stamp. But the ink was killer priced. I'm still thinking on it.
The pic is not of mine but I do have transformer marked with the manufacturer name stamped on like the one you see here. The maker was Ravenswood Electronics in a town called Ravenswood near/in near Chicago. The Chicago pinsiders might be able to shed light on the town of Ravenswood.
Anyway, the transformer in this pic plus one I have are the only two I have seen with the Ravenswood name stamped on. I have no idea how many were tattooed like this. When I get around to marking mine I will probably include the name along with the number.

Awesome! Thanks for the pic. I could make out a couple of the letters on mine but couldn't figure out what it spelled. Now I can see it. My dad has a vinyl cutter so i plan to make a stencil and stencil the name and part number on. It won't be exactly the way it was originally done but will be close enough. That picture is a huge help!

#30 7 days ago

Thinking of the laminars on the transformer.

Any type of metal blackener that promotes oxidation like gun bluing, will give you the rust you need.

Rust or surface oxidation is applied to control the eddy currents because the amorphous surface defeats them.

Its not paint. Lacquer may look nice but its not what you are going for.

You want rust, in a controlled fashion.

An oxidizing lacquer is really good as it limits vibration as well as oxidizing the surface.

I think you can get away with gun bluing (the black kind) and some spray on clear lacquer.

Eddy currents are a nuisance. They kill the power and can cause heat build-up.

#31 7 days ago

Not to get off topic, but how do transformers usually fail? A break in the secondary or primary winding?

#32 7 days ago
Quoted from northvibe:

Not to get off topic, but how do transformers usually fail? A break in the secondary or primary winding?

Exactly.

Or a short in the windings usually caused by vibration or extreme heat (or contaminants like paint thinner or alcohol) scraping off the varnish on the wire allowing it to touch bare wire internally.

You see similar failures on coils that lock on and get smoked.
They short out from the varnish melting off.

#33 7 days ago
Quoted from pinballinreno:

Exactly.
Or a short in the windings usually caused by vibration (or contaminants like paint thinner or alcohol) scraping off the varnish on the wire allowing it to touch bare wire internally.

I have a gottlieb sys1 small transformer that I was told was bad but have not tested. If that is the case, is that something you can take apart, try to spray compressed air through, and visually verify windings then put back together with varnish redo etc. I mean maybe it is worth trying....

#34 7 days ago
Quoted from pinballinreno:

Its not paint. Lacquer may look nice but its not what you are going for.

I did like the OP and wire brushed the surface and painted them black. I have not had any problems (that I know of). Are your saying we have to strip the paint off and do the gun blue thing?

#35 7 days ago
Quoted from cottonm4:

I did like the OP and wire brushed the surface and painted them black. I have not had any problems (that I know of). Are your saying we have to strip the paint off and do the gun blue thing?

Probably there is enough rust on the laminars due to age.
So I think you're ok.

Applying an oxidizer is mostly for fresh metal or if you polished it or removed all the rust.

If there is audible vibration you should investigate that, and either paint it with thin lacquer or take it apart again.

Rusty plates are better than shiny ones.

#36 7 days ago
Quoted from northvibe:

I have a gottlieb sys1 small transformer that I was told was bad but have not tested. If that is the case, is that something you can take apart, try to spray compressed air through, and visually verify windings then put back together with varnish redo etc. I mean maybe it is worth trying....

LOL, theres miles of wire inside a transformer !

#37 7 days ago
Quoted from pinballinreno:

LOL, theres miles of wire inside a transformer !

yeah :/ I guess I just mean the visual ones with the paper off but like you said, probably not where a break would be. can you do a test to see if there is a break in the winding?

#38 7 days ago
Quoted from northvibe:

yeah :/ I guess I just mean the visual ones with the paper off but like you said, probably not where a break would be. can you do a test to see if there is a break in the winding?

You need to know the resistance of a good transformer.

Then you can compare it.

#39 7 days ago
Quoted from pinballinreno:

You need to know the resistance of a good transformer.
Then you can compare it.

Is that ever stated/stamped on the transformer somewhere? If they are pretty consistent for the model, a list of them would be good to have on pinside for anyone wanting to test. Unless this is on the pinwiki already.

#40 7 days ago
Quoted from northvibe:

Is that ever stated/stamped on the transformer somewhere? If they are pretty consistent for the model, a list of them would be good to have on pinside for anyone wanting to test. Unless this is on the pinwiki already.

Its not listed on the unit itself.
There might be information from the manufacturer somewhere...

Without real information all one can do is guess.

A local electric motor rebuilder that rewires armatures can also rebuild a transformer.

They measure the wire thickness and keep track of the length.
There is a spooler machine that does this.

#41 7 days ago
Quoted from pinballinreno:

Thinking of the laminars on the transformer.
Any type of metal blackener that promotes oxidation like gun bluing, will give you the rust you need.
Rust or surface oxidation is applied to control the eddy currents because the amorphous surface defeats them.
Its not paint. Lacquer may look nice but its not what you are going for.
You want rust, in a controlled fashion.
An oxidizing lacquer is really good as it limits vibration as well as oxidizing the surface.
I think you can get away with gun bluing (the black kind) and some spray on clear lacquer.
Eddy currents are a nuisance. They kill the power and can cause heat build-up.

The thing is I didn't do anything to the core plates other than separate them. What ever coating they originally had on them is still there. What ever was put on the plates to "glue" them together is all I separated and it seemed to just be around the edges of most of the plates. I keep them in the exact order they were originally, all I feel I need to do is get them "glued" back together so they won't vibrate. Why wouldn't lacquer work for that? What was on them originally seems to be some sort of lacquer or varnish.

#42 7 days ago
Quoted from ita47:

The thing is I didn't do anything to the core plates other than separate them. What ever coating they originally had on them is still there. What ever was put on the plates to "glue" them together is all I separated and it seemed to just be around the edges of most of the plates. I keep them in the exact order they were originally, all I feel I need to do is get them "glued" back together so they won't vibrate. Why wouldn't lacquer work for that? What was on them originally seems to be some sort of lacquer or varnish.

Lacquer is perfect!

Since you left on the rust, no adjustment is necessary.

You might be able loosen the bolts and pour a little lacquer onto the plates to let it soak in or rub it in, then re-tighten it.

Probably sufficient to take out any noise.

When you are happy, spray paint the plates with black metal etching primer.
It will look better than new.

#43 6 days ago

I worked on the label some more. I can't find an exact match of the font. Does anyone know what font they used originally? This is as close as I could get.
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#44 6 days ago

If you put the lacquer on and apply power while the lacquer is wet maybe the vibration will help it seep down into the plates?

#45 6 days ago
Quoted from ita47:

I worked on the label some more. I can't find an exact match of the font. Does anyone know what font they used originally? This is as close as I could get.
[quoted image][quoted image]

Your numbers look OK. I can see the small difference in the letters. A lot of collective wisdom here may turn up the correct font.

My question is since you are tooling up for a vinyl stencil are you going to be having big black holes in the center of your 6 and 0's? Or is this a stencil with adhesive backing your stick on like Pinball Pimp stencils for a one use only item?

#46 6 days ago
Quoted from cottonm4:

Your numbers look OK. I can see the small difference in the letters. A lot of collective wisdom here may turn up the correct font.
My question is since you are tooling up for a vinyl stencil are you going to be having big black holes in the center of your 6 and 0's? Or is this a stencil with adhesive backing your stick on like Pinball Pimp stencils for a one use only item?

It will be a one time use stencil just like Pinball Pimp, same material. I am in hopes someone out there can tell me what font the original used. I agree what I used is close but there are differences. I won't be making this for a little bit so maybe someone will chime in.

#47 6 days ago
Quoted from Mitch:

If you put the lacquer on and apply power while the lacquer is wet maybe the vibration will help it seep down into the plates?

Lacquer, lacquer thinner, and the fumes are all *extremely* flammable. Do not energize a transformer or game until well after all volatiles have fully dispersed. Some of the worst disasters I've ever seen involved pinball machines and contact cleaner. The solvents in lacquer are no different.

#48 6 days ago
Quoted from semicolin:

Lacquer, lacquer thinner, and the fumes are all *extremely* flammable. Do not energize a transformer or game until well after all volatiles have fully dispersed. Some of the worst disasters I've ever seen involved pinball machines and contact cleaner. The solvents in lacquer are no different.

yep make sure it plenty dry.
Maybe hit it with a hair dryer for good measure.

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