AMI Junction Box Rectifier Replacement

At this age the original selenium rectifiers are getting aged and loosing tolerance. By replacing the rectifier with a new bridge rectifier you will breathe new life into your jukebox. Cleaner power for the mechs and therefore faster movement. The rectifier is responsible for taking AC and converting it to DC used in many motors and other electronics, often a compacitor will be found on the positive yo ground side “smoothing” out the voltage.

A few things you need to know before we get started. The original rectifiers when they failed would “open” meaning no longer contact and just fail. New silicone-based ones can also “short” causing direct connection and could damage your transformer. This is easy to protect against by placing a fuse on either of the AC legs coming from the transformer.

Our rectifier kit comes with an inline fuse holder, fuse, and connectors for the bridge.
Bridges can generate heat, they can benefit from a solid flat mount when possible. Out rectifiers are 35 amp, therefore more than you will need. Heat should be a minimum.

First locate the finned rectifier. On an Ami these are below the chassis and easy to remove with a t bolt. Trace back all the wires. Two will go to the transformer. These are the AC legs. And interchangeable. Mark and desolder to preserve as much wire as possible.

Next you will need to refer to a schematic for the power junction box for your specific jukebox. This can be found in your service manual. If you don’t have one it’s highly recommended to pick one up from our manual sections. Below are some pictures from the AMI F manual.

Mark and desolder the positive and negative wires. Some jukebox power supply and schematics won’t have a negative, simply don’t connect this leg of the bridge. Remove old rectifier.

Before mounting the new bridge locate the terminal markings. I like to put a sharpie dot on the front so I can ID them once mounted. Red for positive and black for negative. The AC terminals are marked with a ~ symbol. For the F or G you can use the same mounting bolt just backwards to hold it to the same location.

One ac line from the transformer should have the inline fuse installed. The other can be directly connected. You can use the supplied spade connectors or solder directly. The positive wire connects to the positive terminal. The negative (if present) directly to the negative terminal.

Keep in mind now your DC power level is restored or may be better than original with modern components. It’s not uncommon to have to bump up the value of the mech fuse. Start with .5 amp same type and then try 1 amp higher if that keeps blowing. Also a good time to lubricate all moving parts.

Upgrades I have seen done. Use at your own risk and all optional. For cases where the negative is not used. You can tie it into a negative. Some understanding of the power supply will be needed to do this. Also optional yo add a smoothing compacitor to the output. Recommend double the voltage and 2000uf. For Ami I would use a 100v electrolytic. Higher won’t hurt anything. Any upgrade might cause more draw on the mech fuse.

Thanks for reading the article. I hope this helps you maintain your jukebox safely.

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