exxos's Atari, Amiga & retro forum

As TF was kind enough to send me one of the second batch of TF536 boards to build and test I decided to modify the Original AwesomeInferno re-locator design to allow the slightly larger design footprint of the 536 board to clear the two large 3300uf caps on the A500.

I ended up making a few changes :

1. Horizontal 68000 footprint moved down 5.08mm (two pins at 2.54mm pitch) to allow 3300uf cap clearance of the TF536 and riser clearance of the 100uf cap to the left of Paula on the A500
2. Cutout window added inside the horizontal 68000 footprint to allow clearance for the 100uf cap to the left of Paula on the A500+
The window has been cut large to allow for anyone who has has their A500+ recapped with a physically oversized cap in this location for whatever reason.
3. Board rerouted heavily to the left expansion slot side to allow significant additional clearance around the ROM area.

The old problem of the horizontal underside pins hitting the Agnus PLCC socket hasn't been solved but this can be mitigated by clipping the underside pins and solder excess with side cutters from D5 to D12 before installation.

I ordered some prototypes which arrived at the weekend and seem to work well but wasn't happy with some of the track clearances and the window size. I also made a slight booboo on the silk screen. I think I've left enough around the cutout window so that board strength isn't compromised. The 1.6mm PCB is still happy and additional reinforcement is provided once the pin headers for the horizontal socket are soldered up.

I've now made the improvements and will order a revised batch once I get a chance. Everything will be put up on Github once I've proven to myself that the're not completely useless!


Design:
A500 Install
TF536
Clearance around ROM
TF530
TF534
A500+ Installed and windowed cap.

Nice work sir!

Looks good to me. That rom clearance is so much better for those 27c800 or 160s now on an A500+

Well done.

Edit:

I have a design for a support for the TF536 that may work well with that.

Ah great stuff, I've been wanting rom clearance there for ages.

Has this design been proven and released yet? I was about to design an alternative if not the case, otherwise I'd order a set of these.

Thanks.

I ordered some prototypes of the the design shown in the first post but wasn't convinced by the results, specifically the track lengths on the data bus lines varied greatly between longest and shortest. I suspected this was causing me some timing and stability issues when testing.

I modified the design again to include track length tuning. The capacitor clearance cutouts have been retained as they worked well. The original clearance around the ROM has been reduced very slightly due to the changes made in the routing.

The length tuning eats away at the top and bottom copper pours significantly to the point where their utility is probably severely diminished. For this reason I have added a four layer option. The four layer version obviously increases the price significantly when ordering but I reasoned that paying £3 for a board that works is better economy than £1 for a board that doesn't ;)

I currently have these on order so the redesign isn't proven/tested yet. I have attached the Kicad project files including two and four layer Gerbers in case you want to base your own design around the board outline or even take a punt with your hard earned on ordering some... The DRC will complain about some via stitching being too close to the board edge and courtyard overlap but that's by design :)

Let me know if there are any issues running the project files. Kicad version 5.1.6.

Hi! Has your riser been tested yet? In a moment it will be very needed...

madness77 wrote: 09 Jun 2020 22:35 Hi! Has your riser been tested yet? In a moment it will be very needed...

Its in the pile on my desk waiting for the next time i pull an A500 out.

A batch of two and four layer prototypes were delivered about two weeks ago. I built a few of the four layer versions and Initial impressions are good, but I wouldn't want to recommend anything until a man with the knowledge and a lab full of high end test equipment has given them the once over :)

The fit is good on both A500 and A500+, clearing any obstructing caps, and the reduced pad size on the 68000 footprints means they no longer use up half a roll of solder for each build.

There's still enough clearance on the new version with the revised routing to get the extraction tool underneath the ROM with the re-locator+accelerator installed. That's assuming you're using an OEM ROM, 27C400 or ROM emulator with a 40 pin form factor. The re-locator clears a 27C800 on a 500+ but loses removal tool access to the underside at pins 1&42. Revision 5 A500 boards will still need double height leg pins to clear the ROM at all.

At the moment I'm unable to make any sort of meaningful comparison between the performance of the two and four layer versions, or indeed whether the length tuning was effective, but certainly it seems stable so far. I'll report back if I encounter any issues.

Thanks for this riser @go0se I ordered a batch of 4 layer ones from JLC, and they arrived a few days ago, really work very well in my A500+. Really like how the ide port lines up perfectly with the expansion port exit. Have tried with a lot of different software, no problems at all :thumbup: