(Topic ID: 257246)

Classic Stern 16B-6 Transformer Restoration


By ita47

1 year ago



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  • 62 posts
  • 16 Pinsiders participating
  • Latest reply 3 months ago by Poida
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#1 1 year 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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#3 1 year 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 1 year 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 1 year 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 1 year 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 1 year 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 1 year 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 1 year 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 1 year 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 1 year 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 1 year 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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#14 1 year 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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#16 1 year 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/

#19 1 year 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.

#22 1 year 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.

#25 1 year 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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#27 1 year 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.

#29 1 year 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!

#41 1 year 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.

#43 1 year 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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#46 1 year 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.

3 weeks later
#49 11 months ago

Sorry this project got put on the back burner when my daughter wrecked her car. She was ok, but my time has been devoted to fixing her car. Today I decided to get back on this project. I decided to remove the plates again and coat them with Lacquer and reassemble while wet to hopefully "glue" the plates together. Right or wrong this is what I decided to do. I didn't get any pictures of the process because my hands were covered with lacquer, and yes I had nitrile gloves on. I coated one side of each plate and stacked them while wet. I didn't want to coat both sides because I was afraid it would increase thickness too much and I wouldn't be able to get all the plates back in.

I did make one mistake and that was painting the outside of the plates earlier. The lacquer melted the black paint and made a mess. It wouldn't have been so bad if I hadn't already painted the transformer. Once assembled and dry I had to sand the outside and repaint it black again. Do your self a favor and don't paint anything until completely finished.

I will now let the lacquer and paint dry for several days. Then I will be attaching my new wiring harness from Third Coast Pinball and wiring it to my new rectifier board. I also plan on stenciling the part number on top for finishing touches. I will continue to post pictures as I progress.
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#50 11 months ago

After sanding and painting. It's not quite as nice as I was hoping, but considering what I started with I think it looks pretty good. I also have to add the mounting brackets. I know everyone is wondering if this thing will still work and I see no reason it won't. I will find out soon enough.
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7 months later
#53 3 months ago

Yes it did work and turned out pretty good. I still haven’t done the part number stencil on top, but I will eventually. Here are a couple of pics of it finished with the new wiring harness and rectifier board. All voltages checked out like they should.

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3 weeks later
#61 3 months ago
Quoted from barakandl:

As for the mounting parts with the replacement rectifier board... you want the press fit side into the PCB and the screw and nut into the mounting bracket. If the washer bites into the top of the PCB a short could happen.[quoted image]

Thanks for catching my mistake. I will get that switched! Love your products, your the go to for replacement boards for the classic Sterns and Ballys.

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