Catastrophe! Oh noes

Well it seems I'm in a bit of a pickle. My oh-so-important CRT television decided to call it quits, and doesn't take any power in anymore. Now, it's been acting wonky for a while now - it's taken multiple on-off cycles to actually get it to even turn on for a few weeks now, but now it's totally dead.

I had a feeling there might be a swollen cap somewhere in the power distribution, so I took it all apart and sure enough, there was one cap near the flyback transformer that has its top a bit outward instead of straight. 

The capacitor circled in the picture has a swollen top, all others seem normal and just fine. It's a 10 uF 160V High Ripple Current capacitor, so I ordered these Nichicon CS capacitors that should be equivalent to the Nippon Chemicon KHA capacitor that's there originally. 

In the meanwhile, the TV was DUSTY and DIRTY inside. I'll be getting some pressurized air cans and contact cleaners and some IPA to clean it up good, and put it all back and hopefully it helps enough to make it work like it used to - with some massaging and patience. It probably won't though.

Oh and BTW DISCLAIMER: DO NOT OPEN A CRT IF YOU HAVE NO IDEA WHAT YOU ARE DOING. I'm not going to be held responsible in the event of death or injury if you follow my example. I have no idea what I'm doing either, but I've read enough about servicing CRT's to know that the CRT tube acts as a high voltage (we are talking tens of thousands of volts ~20k) capacitor, and if it isn't discharged properly, it can discharge that charge through YOU. Luckily this is not rocket science, so if you are careful, know the risks and know how to make the risks lower, it's all possible to do yourself. I'm not suggesting that you should though!

Anyway, being without a CRT means I need some other way to get the output visible while I'm waiting for the replacement cap. I am of course targeting either a composite out or PAL RGB SCART for my GPU, but currently the SCART receiver part has been snuffed away from me. I have already wired everything to use RGB with 16 colors, and if I modified the Pixel Out ATtiny84 from the KAPE GPU to output composite, I'd have to either sacrifice color or make some real complex modifications to the current breadboard config of the GPU and it would all still result in modifying the underlying wiring that I kinda don't want to.

However. I do have some MC1377 RGB-to-Composite encoder chips. With that, I could have the current wiring as is, and just add a another breadboard to convert the current RGB signal to a composite signal. I could then connect that to my capture card that has composite input, and then use my computer as the output device, and continue on with my project while I either source a new TV or fix the old one.

There are a few problems though. First of all, I tried earlier to use my v1 monochrome composite output with my capture card, and it couldn't sync to the signal at all. Granted, the signal KAPE GPU Pixel Timer generates is a forced 240p/288p signal, which is ...kind of unorthodox and non-standard, yet still the common way earliest game consoles output their low resolutions.

Secondly, I don't have enough breadboards to go around. Now, I COULD probably do some creative re-arrangement and Tetris playing with the positioning of the components on the breadboard, ESPECIALLY because the CMD FIFO chip actually doesn't reside on the breadboard, it just rests on it (as due to subpar leg strength, the contacts were really bad and I had to hack around that with a perfboard and wires), so I could easily move that around. Also, the SIPO for communicating with the UNO that is used for command/data communication with the PC (whilst we debug the chip and create the functionality for use with a 6502 is finished) could be fit on the same breadboard as the KAPE GPU ATmega1284P itself.

Thirdly, The MC1377 needs 12 volts for operation, 10V minimum. It doesn't need to be regulated though, as the MC1377 has an internal regulator for 8.2V. I only have +5V easily available, so I need some way to step-up the +5V. Now, I could probably do it with a charge-pump and a square wave from one of the AVRs, especially since it doesn't need a regulated voltage, but the problem here though? I don't have the needed components. I have only two 1N4004 diodes - I do have the needed capacitors though.

For the charge pump I'd need a triple stage, to account for all the components taking their own toll to get to around 12 volts. Luckily the MC1377 can operate at a max voltage of 14 (and even as high as 15 should be okay to not break the chip) so I don't need to be so precise. However, I need 4 diodes for a triple charge pump. Sooo how do I magically create diodes out of thin air? Well, I do have some NPN transistors at hand. 2, to be precise. I could just wire the collector and the base together, and use the whole thing as a diode. Crude and dirty, but if it works, I'm not gonna complain.

So, with all those obstacles taken care of, I should be able to make some output again from the GPU, once I wire everything together. Now, all of this probably isn't going to be in the PCB design of the KAPE GPU I'm going to do for this project in the near future, as the target is still RGB SCART. However, this setback does really underline the fact that making the GPU modular and the whole system expandable is useful - I could for instance have different GPU cards for different outputs. Or perhaps if I just design the GPU with multiple outputs, like SCART RGB, Composite and/or VGA? If I wire things up properly, I could even design it so that I can change the timings to whatever I want, to be able to output to PAL/NTSC or even VGA.

Anyhow, all of this extra work is probably not needed right away or perhaps never, if I manage to fix the CRT soon or get a replacement in the meanwhile. Let's just hope I figure out a way to see the output of the GPU someway at some point, I wouldn't want to wait 4 weeks for China post and in the end not even get the old CRT fixed. Oh, and if you happen to have a CRT for me, I would be a happy camper! (Or actually, even a small LCD/TFT with a SCART would be golden!)