Episode 204: Ben Heck's ZX Spectrum 2.0 Part 1 Episode

Running the Retroleum DIAGROM shows IC1 and 4 to be an issue, on the original schematic for the spectrum this is the ULA and one of the Multiplexers.

I have replaced the 157's but all still the same.

I am going to look over the schematic and test the board for missing connections and compare with the original ZX Spectrum Schematic.

Slowly getting there, fixed the Air Wires which the one below was the most important.

I get the black screen below now, progress but still I think a lower ram issue.

Mike

I know there was on the original, I remember Ben putting them in, one being the MREQL due to a naming problem, but not sure about Version 3, as it is much different than the one on the show.

I did buy "The ZX Spectrum ULA" just for this.

Mike

I vaguely remember some post-fix bodge wires having to be done. I wonder if we still have any close-up photos...

"The ZX Spectrum ULA" is also a good book to have for reference for this project.

I have removed all the SRAM and it does seem to react correctly, so I wonder if it is the SRAM decoding for the ULA, reset button does seem to react as if it is reading the ROM.

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Mike

Hi,

I have removed the CPU and get exactly the same screen, but no black bars, so that is what leads me to the CPU possibly not reading the ROM or writing to the new SRAM.

Mike

Hi,

I know this is an old topic, but just wondering if anybody has built this, I have had the boards made and built using the Parts list attached, but I am getting an issue on boot see images.

Parts List :- https://docs.google.com/spreadsheets/d/1Vw7Wt83tlDuV_LlnrDvnXtyF9QGz4UiosCHRFFlGcTw/edit?usp=sharing

Has anybody else experienced this.

I get the below issue on switch on powerded with 5V, 12V (Video), some of the blocks are flashing, and the Black bars appear when I press the reset button.

I think it is something to do with the CPU reading the Rom but can't find anything wrong. I have reached out to Ben as well, just awaiting response.

Using the KIT 3 from the Github, opened with EAGLE and gerber files sent to China for Manufacture.

https://github.com/thebenheckshow/204-tbhs-zx-kit

I have had my Scope in it and check various signals and all voltages, changed the SRAM and ROM out but still the same issue.

Hope someone out there can point me in the right direction.

Thanks

Mike

That's from a ZX81 - it may not work.

Hello Ben, Great work. I'm interested to build your project. Can you tell me please if this ULA chip(https://www.ebay.com/itm/ci-Ula-2C184-E-ic-ULA2C184E-Ula-logic-Chip-PLA010/202361632265?hash=item2f1db17609%3Ag%3AF-YAAOSwmypbPh9B&_sacat=0&_nkw=+ULA+2C184+E&_from=R40&rt=nc&_trksid=m570.l1313) is compatible with your project? I want to buy this, and this is the only version I've found for sale. Thanks!

Hi!

It is a impresive work.

After review the STL files to print the enclosure, I have a doubt. The files finisished with the word "test" ("back test.stl" & "front test.stl") are necessary for the final design?

thanks in advance.