Greg's Geekery

Пікірлер

@Mrshoujo 4 ай бұрын

I hope you grabbed Rev C BASIC.

@waltciii3 6 ай бұрын

Flip your luma chroma on the board so the cables match better.

@kevin34ct 7 ай бұрын

When working with bare braided wires, tin the leads. It will save you a lot of aggravation. Also the best mod for video is the Sophia2DVI. With an 800XL it's just pop out the GTIA out of the socket and insert the mod. There is even a longer cable and cover to replace the parallel port cover with the DVI connector. I just took out my RF modulator and cut a hole in the case to put the DVI connector in.

@christopherdavis5544 10 ай бұрын

C56 was fitted to early XL's to soften up the messy image from the RF modulator. It was removed in later revisions. The colour pot needs adjusting to correct the too blue picture. There are utilities online to help.

@blackterminal 10 ай бұрын

There is a risk of the old key plungers snapping when you remove keys.

@Adam_Lyskawa 11 ай бұрын

This capacitor was Atari's "hardware anti-aliasing" ;) It worked in horizontal direction only, but back in the days we played games on 8-bit computers - in the highest resolution the pixels were not (that) visible. So - people who know 8-bit graphics only from emulations or modern LCD displays - it's not how it looked back in the days. On a TV (most users had) a pixel was just a fuzzy dot.

@blackterminal 10 ай бұрын

Using these computers on a lcd is not how it should be. Crt is the way.

@buriedbits6027 Жыл бұрын

Great! What an improvement.

@buriedbits6027 Жыл бұрын

14:00 In your video demonstrating the repair of an Atari 800XL, the removal of a capacitor resulted in a sharper image when connected to a flat screen using an RCA video plug (composite connection). Conversely, having the capacitor in circuit softened the image. I hypothesize that Atari deliberately invested in this additional part, despite it causing image blurriness on LCD screens, because CRT televisions dominated the market at the time. As a consumer computer designed for CRT displays, Atari might have opted for this capacitor in circuit, accepting the slight blurriness for better display quality on CRT tubes. This theory suggests a deliberate choice made by Atari to optimize display output for the prevalent technology of that era.

@blackterminal 10 ай бұрын

I would not be removing parts.

@fourthhorseman4531 Жыл бұрын

Just removed that cap on my 800XL and definitely saw improvement in the image as a result. Thanks for passing along the tip!

@GerardPinzone Жыл бұрын

Is that Rev B Atari Basic (what came with the XL) or the newer Rev C?

@prozacgodretro Жыл бұрын

Protip! Wipe down the solder wick with some extra flux (I think they tend to have flux in them) really helps just suck the solder out of a via!

@gamedoutgamer Жыл бұрын

Well done! Congrats! The comparison of resistor connected vs unconnected was great. Some editing of your video to quicken the pace will improve it's watchability if that's a word. =) Please do more A8 vids.

@gregsgeekery Жыл бұрын

Thanks for the feedback, Much appreciated. Still pretty novice at editing, but yeah a lot of the soldering and stuff could be cut or fast forward. I'm thinking to try to address the jail-bars (although they are pretty minor). As @adriansdigitalbasement mentioned, you can supposedly remove another capacitor, but it has a downside. I may experiment to see if I can overcome that.

@gamedoutgamer Жыл бұрын

@@gregsgeekery For the amount of effort and cost (none) what you did is great and acceptable. There is however the Super Video 2.0 (or higher) community created guide to improve video but I think what you've done is ideal. Alternatively there is a post by Wilheim - "In my case, I replaced R56 with a small transistor circuit similar to the chroma signal extraction from the xe models. It improved the image a lot and I didn’t have to add a switch for composite video." So he probably also removed C54 because that's what improves video after removing C56 but disables composite. The topic on AtariAge is forums atariage c m topic/326587-800xl-s-video-fix/

@mikeziniti Жыл бұрын

If anyone is still looking for this info, I swapped my fan out for a 120V 80mm case fan I got on Amazon for about 15 bucks.

@Muldrf Жыл бұрын

The Nabu I received in December had the noisy fan, and only displays a black screen, which I am hoping it can be fixed. The Nabu I received yesterday I am sure has a stuck fan, as there is no airflow and I hear an electrical buzz, which I believe is he bound up fan motor. Oddly the Nabu that had the fan noise in December, did not make a noise and appeared to be working well this morning when I checked if it was still just a black screen.

@gregsgeekery Жыл бұрын

The fan issue is not likely related to the black screen. these don't get very hot right away and will work for a while without the fan. As far as the black screen, check out this video: kzbin.info/www/bejne/bXfPqaGEframpq8 The guy there created a diagnostic guide for NABU by socketing nearly every chip, then removing them one at a time and capturing the symptoms. There's some content there about blank screen.

@Muldrf Жыл бұрын

@@gregsgeekery I checked the video and looked at the guide a bit. Thanks. I wouldn't expect the fan to be related to the black screen. The one with the locked fan is the one working anyways. The screen is black but there is a video signal, I was hoping it was the rom as I found it said that is a common cause for it on an MSX computer. I certainly don't know what the system would do without a working cpu etc. I was also wondering if it would be a bodge wire on the bottom that came loose in shipping. If so the guide could be helpful.

@proteusbridge Жыл бұрын

Mine has a stuck fan and bad video. I emailed PellMill to see if there was anything to be done for exchange/etc. Thanks for this video!

@JimmWare 2 жыл бұрын

1000 Apologies. Yes, I understand that there is a fan/shroud issue in many units. If I fixed the fans myself, two things would happen. 1.) Over 1/2 of you, who have your NABU Computers, wouldn’t have them yet (because of all the time spent fixing fans). 2.) The price of the computers would double to $120.00 to justify all the time spent fixing fans. It was a simple executive decision. Get them out there “cheap” and get them out there “quick”. I hope you understand my position.

@gregsgeekery 2 жыл бұрын

No worries, you made the right call! I appreciated actually having to fix something since I enjoy diagnosis and repair as much as just having something. :). And this is an issue that can be fully resolved without compromise, either the way I did it, or the simpler fix of replacing the fan.

@gregsgeekery 2 жыл бұрын

Hi James, I may have missed it if posted elsewhere, but do you have any info to share about when/if more units will be sold? Should I just keep searching for NABU on eBay daily?

@DennoWiggle 2 жыл бұрын

I tried three scenarios with three different colours. 1. CV connector built into LCD(A) gives blue picture. 2. Composite to HDMI convertor to same LCD(A) gives a blue-purple screen. 3. Same Composite to HDMI convertor to different LCD(B) gives a purple screen. The Nabu circuit has 39R + 470R on the TMS9918A output. I did play around with adding a parallel resistor to the 470R and it had the effect on screen (3) of moving the purple colour to purple/blue with no change in my picture sharpness. This is what the data sheet says for the video chip output on the Nabu. 3.4.1 TMS9918A Monitor Interface (Page 3-5) Typically a 330ohm resistor is recommended to provide a 1.9-volt synchronization level. The load resistor defines the sharpness of the edges on the video signals. A lower resistor value gives faster fall times and a sharper picture. In addition I did add a 33R series resistor as suggested by @JohnsBasement on the Composite video cable which brought voltage levels more into the desired range, but there was little change to the picture sharpness or colour in my case.

@geekwithsocialskills 2 жыл бұрын

I got my unit mid November 2022. You can add my NABU PC to the list that had a stuck fan as well. It makes sense they would be sort of stuck after sitting in the same position for almost 40 years, but the rubbing seems like a defect from the factory. I ended up taking it apart and using my demel on each blade and also on the shroud to make extra sure it would be good. It runs great now and nice air flow. I did record some footage of the noise mine was making. I've been recording all sorts of bits and bobs and today I'm finally putting them all together in a video. I'll be sure to stick in my NABU fan noise clip in the video for historical purposes.

@Ty_Mathieson 2 жыл бұрын

Got my NABU up and running today and pulled the cover. The video background is certainly blue, and darker than that presented by John's Basement, but the resolution when using composite is not looking very good, and I noticed the TMS9918 is getting screaming hot. Like not going to last very long kind of hot, so something seems off to me. All my gear is in storage as I am selling my house so this will have to wait for a month or two before I can look closer at it. Please let me know if your video chip is getting crazy hot as well.

@gregsgeekery 2 жыл бұрын

Unfortunately, I don't have any way to measure the temperature at the moment. I can hold my finger in the center over the die for about 10 seconds, so it does get hot and is definitely the hottest chip in the system. For a relative comparison, on the large resistor just to the left of the 9918, I can only hold my finger there for about 1 second, so it's hotter than the 9918. BTW, that resistor won't heat up if the keyboard is not connected.

@JohnsBasement 2 жыл бұрын

@@gregsgeekery My VDP /never/ gets that hot. Mine only gets mildly warm.

@JohnsBasement 2 жыл бұрын

Greg, I have yet to tweak that trimmer load-cap on my NABU. If it alters the frequency then it will likely show up as a phase-shift when measured over time. Since phase-angle = color,...

@alphaseinor 2 жыл бұрын

Do you think Greg should check the dc offset? His didn’t look washed out like yours does, but it is the wrong color.

@JohnsBasement 2 жыл бұрын

@@alphaseinor His looks a smidge better than mine. So maybe that's related. I discuss how I am viewing at mine here: kzbin.info/www/bejne/jJmtfXSqhruUkLs

@gregsgeekery 2 жыл бұрын

@@JohnsBasement I’ll dig more into this when I get back in town… I’m off for a week and traveling to see family!

@gregsgeekery 2 жыл бұрын

So I rotated that variable cap and it DOES affect the color slightly on mine. it's not a multi-turn, but is 360 degree rotatable. There is definitely one position that is the most solid blue with the sharpest image. in the worst position, it's more purple toned, and has vertical line artifacts with blurry text.

@JohnsBasement 2 жыл бұрын

@@gregsgeekery 🤔... It must change the duty cycle. That, in turn may slightly adjust the alignment of the pixel edges??? You look at it with your scope yet?

@alphaseinor 2 жыл бұрын

In the video circuitry there is an adjustable capacitor, my guess is it's used to adjust the output of the composite video. I don't have mine (yet), so I can't be sure.

@gregsgeekery 2 жыл бұрын

I will check this out next chance I get! Thanks.

@Hacker-at-Large 2 жыл бұрын

Thanks for the heads-up! I found your github repo several days ago and used it to bootstrap my own reverse engineering effort. I have an IDA Pro license, but you might want to check out Ghidra if you need to do any more RE.

@gregsgeekery 2 жыл бұрын

awesome, thanks!

@rog2224 2 жыл бұрын

From "technological paths not taken" perspective, this is fascinating.

@raidenvanbronkhorst5749 2 жыл бұрын

Turns out I had the exact same problem too. This whole time I thought it was just very quiet, but it was getting a little warm. Fan was totally stuck, but sand paper did the trick without needing to move much. Thank you!!

@gregsgeekery 2 жыл бұрын

Glad it helped... definitely some sort of failure mode from the factory... i would not think that the cast metal itself would change size that much just from thermal cycling... but I'm not a materials engineer. Maybe they all got very hot or very cold - or both - at some point in the last 37ish years.

@raidenvanbronkhorst5749 2 жыл бұрын

Great video Greg, subscribed! Looking forward to hearing more.

@gregsgeekery 2 жыл бұрын

Thanks!

@rudolfst 2 жыл бұрын

Great video, thanks I'm really curious: what Brand/Type is the small monitor? It looks really handy on the workbench. Regards, Rudolf, from the Netherlands

@gregsgeekery 2 жыл бұрын

The CRT is a Panasonic WM-CM-1020, and I got it at an auction for like $16. it's well used but has the right retro vibe :) If you mean the LCD its's this one: www.amazon.com/Eyoyo-Monitor-1024x768-Resolution-Portable/dp/B01FHDL1DE/ref=sr_1_3?crid=1LP5GXEEEQ010&keywords=Eyoyo+8+Inch+HDMI+Monitor+1024x768&qid=1670426201&sprefix=eyoyo+8+inch+hdmi+monitor+1024x768+%2Caps%2C360&sr=8-3

@rudolfst 2 жыл бұрын

Ah thanks, I meant the LCD