Issues with homebrew Vectrex

[cBaer]

Hi there.

 

And yes, the system, not a game.

 

I build a homebrew Vectrex, working good, but have still some issues not sorted out.

The calibrations with the Testcart REV4 are looking good enought, but on the title screen the outer lines are a bit off.

On the Homebrew 2048 game the outer line is very off + no round edges and the numbers look horribly.

It seems to affect the Y-Axis the most. I alreday swapped out the chips, however had only similar ones.

See the video:

https://youtu.be/liu6WxhAQeQ

I used the schematics of the service manual, however did some changes:

• VIA is a R65C22P2 (its a CMOS chip).
• "AY-3-8910A from GI", the datecode is 1341CBA maybe fake but it is doing its duties
• opamps are TL082L and TL084L (both UTC)
• DAC is an DAC0808LCN (National semi), the datasheet states that this is a fully compatible replacement for the chip originally used.
• CD4066BE (TI)
• CD4052BE (TI)
• 2N3606 instead of 2N3605
• swapped R303_3.6k with a 10k trimmer
• there are 3 aditional TL082L to optionally invert, amplify and bias the X, Y and Z output to feed my iwatsu SS-5702 Oscilloscope used as the monitor.
• Five integrator capacitors i used 10nF Styroflex (https://www.reichelt.de/styroflex-kondensator-10n-2-styroflex-10n-p19842.html?&trstct=pol_1)
• The digital Part worked first try, so im omitting the chanes I did there.

 

I recreated mostly the logic board and the LM386 Part.

Are there circuits other than that, that limit the bandwidth of the signals? that would explain why the corners are not round.

 

thank you for any hint or advice.

 

P.S.

I have never seen an Vectrex in person so i have nothing to compare to,

and this is a retro computer project because BASIC on a Z80 on an Terminal didn't cut it for me

[Malban]

Hi,

testing your 'Vectrex' with a very sophisticated new homebrew us not really a great idea. Programs from Thomas push the ordinary Vectrex to the limit - there HAVE to be difference when you swap parts like that...

 

But I further guess that not the digital part is slightly off, but only some analog parts.

 

Perhaps it is just the fact, that you use another monitor than the original vectrex CRT Vector monitor.

E.g. your start screen - the Vectrex String is off center - that is the typical display of an

a) 100% digital correct emulator

or

b) the display of a "faster reacting" vector monitor

 

you might look at arcade jasons tryouts connecting the vectrex to an arcade monitor - looks similar ...

All original vectrex games (except cleansweep) work fine but very optimized games look screwed ...

 

E.g. Also look at

http://vide.malban.de/8th-of-november-19-monitore

 

to have a real live test - try to get an original vectrex monitor and connect that one to your board ...