Alvema

I'm positive RF is enabled as I did the modding myself. I tried RF and couldn't tune the signal in the TV, but before modding it I also had a lot of issues tuning the signal in modern TVs, so I think the problem is not with the composite output. Also using composite it sometimes plays Atari noises randomly even without a cartridge inserted (like the sounds make Enduro when accelerating the car or many other games), so I think the composite is working fine.

Hi everybody, I was playing with my 2600 Jr (PAL) for about 1 hour, and suddenly the TV went black and it started playing noises (same as when the cartridge doesn't make a good connection). I power cycled the 2600, and same result. I tried with another cartridge and nothing. I also tried cleaning the contacts and same result. The power light lights on, and sometimes when I power it on start playing noises, but no video signal. It doesn't mind if there is a cartridge or not inserted. I have tested with a multimeter that the power brick is fine. I also have tested another one (universal) with same results. I have disassembled the 2600 and all the capacitors seems fine, the motherboard is pristine (no sign of rust or anything strange). By the way, the 2600 is composite modded. I also have read some guides and the power regulator is also fine (it delivers 5.05 V). I have also replaced the big capacitor as I had another one with the same specs spare, with the same results. I have tried to apply new solder to the main chips although the original solder seems fine, in the case there was some kind of cold solder. Do you think the issue can be produced by the 4.3 uF capacitors (they seems fine) By the one, I have a 500 KHz oscilloscope, in case can be useful, but I don't know what to test. Thank you.

Attached is a PAL60 version of Crackpots I have made. The colors have been taken from another version I found that wasn't working correctly (garbage in the Activision logo). Crackpots (PAL60).bin

Thank you everybody for your comments. I have been working a bit in this project, an I have attached a new version. In this version, there is overflow control for all operations, and it can also calculate square roots and logarithms. Square roots are slow because they use internally a lot of divisions, and that operation isn't optimized at all for now. Anyway if updating the screen is disabled, they don't take very long. Logarithms, as they are calculated partially based on tables, for now they aren't 100% exact. I'll expand that tables as much as possible using the empty space in the ROM when all the code is finished. Most of the code for logarithms will be used also for sin / cos / tan calculations. Next work I'm go to do is code exponentiation, and optimize division. scicalc2600-2.bin

Hi everybody, I'm developing a scientific calculator for the 2600, in the style of a Casio FX-82, or a TI-35. For now, it can manage numbers up to 11 digits (2 decimal), both positive and negative, and can perform the four basic operations and square roots. Also, will manage overflow (for now, only for multiplication). At least I think I'm going to also add some memories, basic trigonometric calculations, logarithm operations and maybe extend it to manage any arbitrary number of decimal digits. Its use is intuitive, use the left joystick to move the cursor over a number or operation, and fire to select it, something like a real calculator. This is the first thing I develop for the Atari 2600, so I'm using Batari Basic, but I have experience with assembly programming, so I'm coding some of the math routines in 6202 assembly, so they can run fast enough. Additions, subtraction and some parts of multiplication are already coded in assembly. Meanwhile, an hourglass can appear if an operation can take some time to perform. If the right difficulty switch is set to A, the display is not updated while performing calculations, and they run many times faster. I'd like to know what appears if it's used on a CRT screen, as don’t have any available. I have attached the first prototype (PAL60 / NTSC). scicalc2600.bin