Search found 829 matches

by krzysiobal
Tue Feb 02, 2021 2:11 am
Forum: Reproduction
Topic: Opening Bandai Famicom carts
Replies: 2
Views: 839

Re: Opening Bandai Famicom carts

No, just ordinary clips on the upper part of shell. Squeeze upper part with clamp.
Because the center bolt hoes all the way up to the PCB and there is almost zero play for it to bend when opening,there is high chance you will break the center pin.
by krzysiobal
Thu Jan 28, 2021 3:07 pm
Forum: NES Hardware and Flash Equipment
Topic: SKROM Schematic?
Replies: 18
Views: 8315

Re: SKROM Schematic?

This 1k resistor is good way for measuring voltage drop and thus calculating how much current the memory draws in standby mode (and determining if this ram was designed to be used for low power appliances or not)
by krzysiobal
Tue Jan 05, 2021 3:40 pm
Forum: NES Hardware and Flash Equipment
Topic: VRC IV pinout
Replies: 25
Views: 31250

Re: VRC IV pinout

This is your PCB. If only one game can be selected, writing to latch (74161) does not work. Either because 1) the /RESET pin is held in, 2) write signal is not generated properly. My suspect is that the value of capacitors you have soldered (C1, C4) are incorrect. C1 should be 1n-10n C4 should be te...
by krzysiobal
Sun Jan 03, 2021 2:13 am
Forum: Reproduction
Topic: Repros work with TI 74LS257 but not Motorola?
Replies: 5
Views: 2109

Re: Repros work with TI 74LS257 but not Motorola?

Any schematic or photo of subjected cartridge to see what is this chip responsible for?
BW. From all cartridges I have analyzed so far, it appeared only twice:

1) Ai Senshi Nicol (FDS port)
sch.png
2) MGC-002 TXC's MMC1 replica
http://forums.nesdev.com/viewtopic.php?f=9&t=17067
by krzysiobal
Sat Jan 02, 2021 6:36 am
Forum: NES Hardware and Flash Equipment
Topic: Replacing mn1026, Ba6162, etc with discrete logic
Replies: 13
Views: 3283

Re: Replacing mn1026, Ba6162, etc with discrete logic

It's not strictly the reset behaviour that makes troubles, but power off. When power is cut off, supply voltage for all chips falls slowly and at some point CPU might start executing garbage opcodes (maybe at 4V or below), potentially overwriting RAM cells. Transistor protection circuit does won't d...
by krzysiobal
Fri Jan 01, 2021 2:29 pm
Forum: NES Hardware and Flash Equipment
Topic: Modifications and upgrades of various console - guide
Replies: 0
Views: 3171

Modifications and upgrades of various console - guide

Modifications and upgrades of various console - guide I decided to gather my experience in repairing / remaking consoles and put them in one place. The post will be gradually expanded (I'm affraid this bbs engine does not support anchors to make hyperlinks to places in my own post) IQ502 rev 1 IQ502...
by krzysiobal
Mon Dec 28, 2020 3:30 pm
Forum: NES Hardware and Flash Equipment
Topic: About WILLEM PC3b 16bit adapter schematic needed
Replies: 1
Views: 1685

Re: About WILLEM PC3b 16bit adapter schematic needed

Hi, I've obtained some 27c160,does anybody have an 16bit adapter schematic, or can anybody tell me how to wire it UP exacly? I need to write 27c160 only. Some Time ago i've borrowed an 16bit adapter without any buffers and it worked well, errors at verification were occasionally. Thanks! This one? ...
by krzysiobal
Mon Dec 28, 2020 7:56 am
Forum: NES Hardware and Flash Equipment
Topic: Famicom Network System (aka Famicom Modem) Investigations
Replies: 114
Views: 65611

Re: Famicom Network System (aka Famicom Modem) Investigations

I am brand new to Eagle and have not used it before. Your program is very easy to use so far. I have had success creating a new project and importing the front and back images of the modem module. I have drawn some thru-hole vias and wires connecting them. It seems to be a very efficient interface,...
by krzysiobal
Sat Dec 19, 2020 5:41 pm
Forum: NES Hardware and Flash Equipment
Topic: City Figher 4 with ext audio (Mapper 266)
Replies: 4
Views: 2023

City Figher 4 with ext audio (Mapper 266)

The whole story started when trying to make repro of City Fighter 4 ( mapper 266 ) https://obrazki.elektroda.pl/2514959500_1608423589.png https://obrazki.elektroda.pl/8600890500_1608423591.png Thanks to wiki, I was able to get how the registers works. It does not say however how the DAC is realized ...
by krzysiobal
Tue Dec 15, 2020 4:09 am
Forum: NES Hardware and Flash Equipment
Topic: DeGlitching ppuA12 on mmc3 by software (vhdl or others)
Replies: 6
Views: 2840

Re: DeGlitching ppuA12 on mmc3 by software (vhdl or others)

Hello, Have nice day! As the title matter. Is possible to deglicthing ppu.a12 on mmc3 by software? Hope your support What do you mean "by software"? In assembler? No. In VHDL without any extra hardware? You can sample the A12 on every edge of m2 and search for a 000001. But better way would be to a...
by krzysiobal
Fri Dec 04, 2020 12:41 am
Forum: NESdev
Topic: Weird SMB3 pirate cart
Replies: 10
Views: 2793

Weird SMB3 pirate cart

I got this cart from a friend for checking. It interested me for two reasons. * First - it is based on the rare pirate MMC3 chip called "88", which has two GND pins and it made me curious if one of them is some kind of mysterious input that, for example, allows to switch it between different modes. ...
by krzysiobal
Wed Dec 02, 2020 11:25 am
Forum: NES Hardware and Flash Equipment
Topic: MultiGame Cartridge Project
Replies: 84
Views: 61332

Re:

During reset signals are high impedance (Hi-Z), not logically high. But then there should be an (possibly internal) pull up or something because it goes logic level 1 when reset is held. The Hi-Z state applies to a stock 6502, right ? M2, CPU-A14 and CPU-A13 are tied to 74'139's inputs in multi-chi...
by krzysiobal
Mon Nov 30, 2020 9:59 am
Forum: NES Hardware and Flash Equipment
Topic: Reset based multicart cartridge issues
Replies: 2
Views: 2605

Reset based multicart cartridge issues

I was always amazed how the 2-in-1, 4-in-1 or even 8-in-1 multicarts works so you can press reset button and it switches to next game flawlessly. They're built using 74ls74 but the filtered m2 signal, which is restored +RESET, has so slow rising edges it shouldn't work (7474 does not have Schmitt tr...
by krzysiobal
Fri Nov 27, 2020 1:26 pm
Forum: NES Hardware and Flash Equipment
Topic: Famicom Network System (aka Famicom Modem) Investigations
Replies: 114
Views: 65611

Re: Famicom Network System (aka Famicom Modem) Investigations

Man, I appreciate the enourmous amount of work you did. Sorry I did not mention this earlier, but few years ago I made a program that helps such things (KrzysioPCB). All you need to do do is load PCB images, mark all the pins, redraw all tracks, assign PADS to devices and it generates eagle schemati...
by krzysiobal
Wed Nov 25, 2020 12:50 pm
Forum: Other Retro Dev
Topic: DOS VGA Tricks
Replies: 37
Views: 10739

Re: DOS VGA Tricks

This will be about tricks in text mode. 0) As far as I remember, DOS can offer 3 video modes for text display: * 8x16 characters (most typically used) * 8x14 characters (used quite rarely, for example - in the BIOS start screen (when EPA Pollution Preventer logo is shown) * 8x8 characters 1) There i...