JROK component board + A500 (update)

[Damion]

Just wanted you let you guys know... I picked up my JROK component board at the PO today, did some quick soldering to the video plug from my disassembled A520, and voila... beautiful, perfect component video.

I've only tested NTSC low-res, I'm sure PAL would work fine, but my old 60" Mitsubishi CRT projector doesn't like the signal -- picture rolls vertically. (I'm 100% certain it will work fine with a display that's PAL compatible.) I haven't had time to test it with my other amigas yet (going out to drink tons of Spaten Optimator and eat Schnitzel for my 30th tonight), but no doubt it will work fine.

Also, it's going to fit almost perfectly into the A520 case. James provides a drilling template which should simplify things. I'll try to do some more testing, and maybe get a few pics up as I have time. This should look great with a 480p 15" LCD TV.

cheers

[Damion]

Sweet! Happy B-Day man! Upload some pics!

Thanks dude! I had fun last night... but definitely drank too much Franziskaner... LOL

Is there a tracking control or adjustment knob to fix those issues?

Not on the jrok unit itself, however I think the problem is that my television just doesn't like 50 Hz. There are a few NTSC/PAL TVs out there I'm looking at, though. Technically, both the jrok and neobitz should handle both PAL and NTSC component fine. S-VIDEO (and probably composite) is what presents a small issue, since the encoder chips require slighly different timings. (Note that for component video, there's really no "encoder chip" as with s-vid and composite.)  

 

Sounds like a fun project. This guy is awesome! I would love to have half of this guy's knowledge (and apparent free time ) What's the availability of replacement C64 PLAs and C128 MMUs? This guy could probably whip one up in a day. I bet a 6526 or 8520 could be emulated as well.

I'm pretty happy that I might finally have a nice display for my old machines again! Now if I can find the right LCD TV, there won't be any need for scandoublers, flicker-fixers, or giant, eye-mutilating CRTs.

Anyhow, I'm going to try to break through my brain-fog, finish this up and get a few pics up today.

cheers

[Damion]

Gentlemen, my apologies for the delay.

Here are a few shots of what I've done. Everything seems to work fine... however, I won't be able to better assess the picture quality until my LCD TV arrives, hopefully by Friday. My current TV seems to have a slight power ripple (or something) interfering with the picture (faintly on every input), so I need something else to test with.

The drilling came out 90% to my expectations, which is pretty good since I wasn't able to use a drill-press. I simply cut and taped the supplied template where I wanted it on the plastic, and carefully drilled, starting very small and gradually working up.

I had to shave a bit of plastic from the inside of the casing in order for the unit to fit. (Also, I drilled a small hole for the LED... looks pretty cool in the dark. :-)) Since I was concerned about thinning out the side of the casing too much (and it fits firmly and perfect as is), I decided not to glue in some type of mounting to better fasten the PCB.

For anyone who is interested, the version with s-video and composite jacks would also easily fit, it would just require a little more install time and possibly a different placement within the A520.

Photo 1

Photo 2

Photo 3 (warning, "carpet shot" may be inappropriate)

Photo 4


@Tomas

They come fully assembled! The only thing you'd have to do is fit it into the A520 case and solder a few wires, so, while time consuming, it's not too difficult. Installation inside a "big box" or tower amiga would even be easier.

@doctorq

Exactly! Pretty simple. Just keep in mind that s-video and composite will require specific PAL/NTSC wiring, whilst component does not. However, since you guys have SCART, that would seem to be your best option, that is unless I'm missing something.

 
cheers :pint:

[Damion]

Well, my 640x480, scan-doubling, flicker-fixing, NTSC/PAL LCD TV arrived today.

I wish I could say everything is perfect, but unfortunately, it isn't working out as well as I had anticipated.

Broken down to positives and negatives:

+ The Sharp Aquos LCD I picked up does indeed scan-double, and, surprisingly, there is absolutely ZERO flicker in the NTSC laced modes. Super-High-Res modes are downscaled and displayed OK.

- There is something wrong with PAL modes. The first 1/3 of the screen looks fine, but there's distortion in the rest of the picture. Text looks kind of chopped up and separated. Major bummer, since the LCD is advertised as being PAL/NTSC/SECAM compatibile (specifically with component input), and even my old 1084s handles PAL. Could be the jrok (but theoretically it shouldn't be).

- I'm uncertain about the JROK's video quality. There was still some weird interference, adjusting the pots on the jrok seemed to eliminate most of it, but then the colors go out of whack since the adjustments aren't the same between the three. Text isn't as clear as I think it should be, and edges aren't very crisp. I'll have to play around with it some more I guess.

I'm going to try a better set of cables, but as of now, I cannot recommend the jrok board for amiga use. Maybe the neobitz component output is of better quality, maybe my expectations are simply too high... I dunno... but I'm not sure how much more money I want to throw at this.

This is a total bummer, because

-- I need something which displays PAL correctly, since for me, amiga is all about watching demos

-- I can't handle 50 Hz refresh flicker, so CRTs are not an option

-- 16-bit flicker-fixers are teh lame for AGA, and don't usually work with LCD

-- WinUAE is great, but I wanted to resurrect my "real" hardware. (...and now I recall exactly why I sold everything years ago, LOL. "Real amigas" are indeed very cool, but also a serious PITA... and I will laugh until I piss myself the next time someone starts a "why can't wintel 'just work' like amiga does" thread)

cheers... if anything else notable happens I will post it here. :/

[Damion]

amiga_3k wrote:
You might try shielding (and proper ground it) of the internal cables and even the complete unit. Might be that you're picking up some EMC noise from the A500.

Thank you, that's definitely good advice. I'm going to use the original A520 shield (which should fit perfectly), and improve grounding. I've managed to all but eliminate the strange artifacts by carefully adjusting the pots. Also, I think I've found yet another LCD to try for PAL modes. :p


 

[Damion]

Made a couple of observations today...

The PAL image distortion is definitely the LCD TV, and not the JROK. I'm getting the same exact distortion from the composite output on my A1200. This is quite annoying, since the LCD has settings for like 4 different types of PAL.

The poor text display is a combination of the JROK (get to that in a minute) and the LCD. The LCD adds a certain "softness" to video, regardless of input. I'm not sure why exactly (a result of the comb filter??), and while it's an interesting effect for video and gaming, it's not good for small text. (Perfect Dark via s-vid on the N64 looks AWESOME though.)

The JROK is adding it's own interference to the amiga's video output. Even while using the A1200's composite port, the JROK will screw the signal a little. It could be a grounding/shielding problem... but unfortunately, it seems I'm not the only one with this "interference" issue.

Adding to all of this is the fact that the quality difference between component and RGB, while not extreme, is noticeable.

I hate to say it, but IMHO, the best solution for "classic" amiga displays is either a good CRT that handles 15Khz, or a scan-doubler and good quality CRT PC monitor. 50Hz hurts the eyes after a while, but at least it's clear. LCD TV softening (making small text blurry), smearing effects, and reduced quality of component output VS RGB make it NOT a good option... though it might be a cool "novelty" factor on a big-screen.

Anyhow, time to forget about it for now and have a :pint:


cheers

[Damion]

Just a little update on this...

I managed to improve the image quality somewhat, first by buying a better video cable (moderate improvement), and also by using a high quality ATX PSU instead of the standard A500 unit.

Interestingly, I found that every Amiga I tried (A500, A600 and A1200) had some noise on the csync output. Therefore (and with a little advice from JROK), I hit the local electronics shop, picked up an XOR gate IC and used the separate H and V sync outputs instead of the csync. (The XOR gate then combines the two into a "csync" signal needed by the encoder.)

This made a noticeable improvement also, and now I'd say the picture is about 85% of what I had originally hoped. There is still some unacceptable text ghosting, and also a bit of "grainy" interference that affects certain colors. (I can adjust the RGB pots to eliminate the "grainy" noise in one color, but then it appears in another, and so on.)

Anyway... although it's a fact this device works excellent for many (and admittedly, it's not "intended" for the amiga), I'm still struggling to get the beautiful, almost noise-free image I have via RGBHV and the 'ol 1084.

I'm going to fool with a few other things, in addition to ordering the neobitz (component version), and giving that a shot as well.
 

Regards,

Damion