Interface 1 Rom Upgrade

[cj7hawk]

As an accomplished threadmancer, I once again raise this thread from the dead, though mainly to make my first post and thank those who contributed to this thread before me, since it helped me out.

I recently bought a faulty Interface 1 that was crashing the Spectrum when an Interface 1 command was tried. After a little guesswork, I decided to desolder the ROM rather than ordering a new ULA. It was the right move. Bit 3 of the ROM had failed and a hex dump showed all the second nibbles were 8 or higher, indicating it was reading high.

The 4764 threw me a little at first, but then I noticed most of it's pins were aligned with the 27128, which allowed me to install it in it's place. It's a tight fit, but it does fit OK. I burned the v1 and v2 roms into it, which was fortunate, because the Version4 PCB only works with the v2 ROM, and it wouldn't be good to replace the ROM twice in this interface. Burning the v2 into the upper space ( 2000-3FFF ) allowed me to switch between them once it was installed.

I burned the 27127 and just cut the pins that didn't match the 4764 and bent them upwards to allow soldering of wires. There's only a few wires, so it's not a difficult task. Then I installed the 27127 in the 4764's socket and soldering in the extended A11 and A12 lines, gave it power and permanently wired CS to Gnd.

It works OK. A quick fix.

I pic in case anyone else needs to try this;

[Kratulio]

Hello.
I'm writing in this old thread becuase it's the only real explaination about how to get rid of a ROM malfunction.
Thank you for all your hints and lessons

I'd like to read the ROM i have on my faulty IF1 but i get only FF.
I've tried it as 2764 with adapter , without adapter etc..
@Derek : can you tell me which adapter you built for your ALL03 and device TMS2564 ?

Thanks in advance,
Stefano

[DR400]

Inspired by this thread, and wanting to get an Interface 1 working and “future proofed”, I have replace the ROM and the UAL in my IF 1.

Happy to report it all works 100% and thought I would share with the forum as it may help others.

I purchased a modern ULA replacement from https://vdrivezx.com/vla1-sinclair-inte ... placement/ as I knew the ULA was faulty, it did not show the usual burnt plastic on the shell of the interface and did not stop the spectrum from booting, just no activity from the interface and Vdrive.

I also decided to replace the ROM as this also can fail as previous post show, I used a https://www.retroleum.co.uk/c64-chips switchable rom with version 1 & 2 of the Interface ROM’s. See the excellent Retroleum website for details.

The ROM chip is a direct replacement for the original Sinclair ROM and no bent pins, cut tracks or mods are required.
I also replaced the 3 capacitors, although the originals tested within tolerance.

First I removed the edge connector as I thought it would be easier to remove the ROM and as I was replacing the ULA as well, I wanted to make sure I did not damage any track as the solder had wicked up through the component side and aware of how delicate Sinclair PCB’ s and how easily the tracks and via’s can be damaged.

I know removing the edge connector was risky, but just wanted to make sure the ROM and ULA pads and tracks were not damaged and removed cleanly.

I used a desolder gun to remove a much solder as possible, then hot air to help the ROM and ULA from the PCB, thankfully all pads and track remained intact.

I have new replica PCB I was going to use if damage occurred while removing the components, but as all was OK, that can wait for another IF 1 that needs work.

On replacing the ROM, ULA and edge connector, it worked first time, hopefully will be OK for the next 40 years!

Hope this is useful to others thinking of repairing your Interface 1.
Regards

Edge connector removed:

Rom Removed

Done!

[1024MAK]

Nice work there DR400

Well done

And thank you for posting.

Mark

[DR400]

Nice work there DR400

Well done

And thank you for posting.

Mark

Thank you, also forgot to add this link that gave the info to get a replacement ROM or build a adaptor board if you wanted to program your own version.

https://github.com/liveboxandy/ZX-Inter ... cement-ROM

Regards