Possibility of complete redesign and modern manufacture of LC-LC475 power supplies

[landogriffin]

Inquiring minds want to know.... any update? Is there anything I can help with?

I had a LC power supply die, so of course it's easier to design a new one than just get one off eBay ;-)

 

[Androda]

Currently we're waiting on a second revision protection PCB to be made. I forgot to include the revision in my last order, which means this new revision is probably going to be waiting through Chinese New Year. The order is in, 75% completion, and the new year just started.

Previous PCB was just the tiniest bit too wide and scrapes / pushes on the sides of the mounting bracket. It also only had one notch for the power supply's mounting hole where there should have been two.

After the protection PCB is done, the mounting bracket needs final screw hole locations and then we could start selling the printed bracket style.

This project has taken a very long time, mostly because I keep getting buried under bluescsi related things.

 

[landogriffin]

This project has taken a very long time, mostly because I keep getting buried under bluescsi related things.

There are never enough hours in the day for fun projects!

Please let me know if you need a beta tester, someone to help with the bracket updates or anything else. This is a cool project!

Just curious - were you planning to "open source" the PCB hardware design and/or bracket model?

 

[Androda]

It's been way too long since posting a status update here, sorry.

The design which uses a power supply that provides 12/5/-5 directly (no down-converters) isn't going to be very affordable. These power supplies have spiked in cost and are near-unavailable due to the parts shortage. We'd be looking at more than $50 for a kit that needs to be assembled, and that's just not a great price in my opinion. I have five of these power supplies on hand (plus four protection boards), so if you really need one DM me and we can talk about it. Given the cost here, I am leaning toward releasing my side of the design for personal use along with a parts list so you can just make your own.

To try and make the design more available and not rely on that special 12/5/-5 supply, I have started yet another iteration of the down-converter style which uses a plain old 12v adapter as the primary source. This one is targeted at being 90% assembled by the PCB maker: to decrease the time cost, make kit assembly simpler, etc. The price range is uncertain, as I haven't committed to a run of the boards yet (might be a few last minute changes). But this should hopefully cost less than either of the two previous designs. Will post back later once I know for sure.

 

[Androda]

Tested the first prototype of this design (external 12v brick), and it worked - booted my LC III. Barrel jack input (2.5mm center pin) on the left, 12 to 5 buck chip and an inverter hanging off the 5v to get -5. Fuses and protection zeners built in, to safeguard your Mac.

The final design might be a two-PCB system. One small board will sit at the back and hold the barrel jack input and power switch (this prototype PCB has through-holes for a switch but was jumpered to be always on). That smaller power-in board will connect to this main board. Would allow a more normal look, with switch at the back.

This design can be cheaper than the previous ones (Around $32 for a kit), for one simple reason: The 12v supply is external, not integrated, and the $30-ish kit doesn't include the 12v supply. That 12v supply can be had for around $13 to $20 depending on how nice you want to go.

So really it's not much cheaper than the previous design, as the total for a kit climbs close to $45 when the power supply is included. But this design has one small advantage, for the case where you have several LCs and only use one at a time. The external 12v brick can easily be swapped between LCs that use this internal board.

I've been unable to find ways to lower the price further, and it's rather frustrating. Even this design, using a cheaper and more available buck regulator ends up costing just a few dollars less overall.

 

[Androda]

Designs for these have been released here (Creative Commons Non-Commercial) : https://github.com/androda/PCBDesigns/tree/main/PowerSupplies
They are currently badly documented because it's been so long since I looked at them.

Both designs worked in both of the LCs I tested, LC II and III.

The RPT-60A design is easier given that you can just use the RPT-60A power supply directly if you'd like with extention wires. That's not as safe as using the protector board in the repo, given that power supplies sometimes fail out of regulation and we don't really want to blast your vintage Mac with unregulated voltage.