Phil C's Raven build

[dml]

Oh..... that's nice

[PhilC]

Not a good et4000/W32i day today. The first chip I tried didn't work in the new board, so I took the chip off my other working card and have managed to lift a couple of tracks off the working board whilst I was at it

Hopefully tomorrow will be a better day.

[PhilC]

Bit of better news today. I have the new VGA card working but the display is very dark in text mode and dark and garbled in windows.

Checking the BOM against the schematic there are some inconsistencies in two of the resistor arrays and possibly others, 300 ohm on schematic and 30 ohm on the BOM. I'm going to have to go a bit of datasheet googling and work out what I really should have. Then there's next to no voltage on the RGB, when there should be up to 0.7v.

At least the card is nearly working now.

[dml]

Bit of better news today. I have the new VGA card working
....
At least the card is nearly working now.

Sounds like the build documentation on that project is a bit random but encouraging that you're getting an image. I'm sure you'll figure out the missing facts!

But how on earth did you find the non-AX TSENG chip? They all seem to be attached to £400 cards!

[PhilC]

Bit of better news today. I have the new VGA card working
....
At least the card is nearly working now.

Sounds like the build documentation on that project is a bit random but encouraging that you're getting an image. I'm sure you'll figure out the missing facts!

But how on earth did you find the non-AX TSENG chip? They all seem to be attached to £400 cards!

I actually took it from a card that cost me £75. You find them on some odd video processing or video conferencing cards if you know where to look.

May have a source for chips but likely at £50 a time.

[PhilC]

Bit more progress on the video card today,

I managed to find the brightness issue and traced it back to the DAC reference voltage being too high. This was because the LM385 silkscreen is backwards. Reversing that and I've now got full brightness but glitching on the screen, which may be due to the resistor valves in the two resistor networks. I'll try the 300 ohm suggested on the schematic tomorrow and see what happens. The resistor arrays are acting as delays for the ram logic, so likely something wrong there as when loaded into windows, the screen is totally unreadable.

Once I've got this all worked out I'll send on the other boards to those who are interested and then I'll redesign the board to use SMT and some other memory that's easier to locate. And try and sort that ridiculous delay resistor issue out as well.

[PhilC]

So a bit of good news today.

The Excelgraph ET400/W32i works just fine on the Raven! It does some odd stuff if I select interleave in the bios menu but otherwise it works great so far. Other than a bit of ghosting, I'm very happy with it.

PXL_20250713_140035684.MP~2.jpg (348.18 KiB) Viewed 1473 times

[dml]

That's great! Impressive work getting that up and running.

[PhilC]

That's great! Impressive work getting that up and running.

Thank you. Still want to build one?

[dml]

Thank you. Still want to build one?

Yes still interested in building one, despite not having the needed parts I do have the DAC but the RAM & W32i is going to take some time, patience and luck I think.