Improve your C64's video output with this simple fix
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- Опубликовано: 8 авг 2024
- Part 2 of 2: More on improving the C64 video quality. In this video I explain you why the C64 video quality can be improved and exactly how to do it. Massive improvement!
Part 1: • C64 video output: Is t...
0:00 - Intro
1:22 - Deeper look at the RF Mod bypass board from part 1 including issues and a fix
3:11 - tebl's RF modulator replacement
5:03 - Viewer comments: "An easy trick to improve the C64 video quality?" Nope.
6:56 - The 250407 C64: Let's get started fixing the video quality!
7:35 - What are the different C64 RF modulators and what are their issues?
12:48 - What are the problems with the MD6-VA3403 NTSC modulator?
18:03 - *** How to modify the MD6-VA3403 NTSC modulator on the 250407 to make it super sharp
24:50 - Testing the results of the mod over composite, S-video and on a real CRT
27:13 - What are the problems with the MD6-UE3603 PAL modulator?
29:10 - *** How to modify the MD6-UE3603 PAL modulator on the 250407 and KU boards to make it sharp
31:10 - Testing the results of the mod -- why is it still a little soft?
33:15 - What are the problems with the MD6-VA3405 NTSC modulator?
35:00 - *** How to modify the MD6-VA3405 NTSC modulator
35:30 - Let's talk Hanover Bars and the annoying issue with C64 PAL output
38:15 - Conclusion
MD6-VA3403 and MD6-UE3603 is used on:
Longboard 250407 PAL/NTSC
Longboard KU-14194HB PAL
MDA-VA3405 is used on:
Longboard 250425, 250441 and 250466
--- Video Links
tebl's RF Modulator Delete
github.com/tebl/C64-Modulator...
Another RF Modulator project: (not shown in the video)
github.com/mbarszcz-pcb/c64-r...
RF Mod Picture Improvement
www.nightfallcrew.com/29/01/2...
Hanover Bars: (Wikipedia)
en.wikipedia.org/wiki/Hanover...
Play With Colors 2: (PAL only)
csdb.dk/release/?id=50556
EasyFlash 3
store.go4retro.com/easyflash-3/
Adrian's Tools (for the EasyFlash 3)
github.com/misterblack1/ef3-c...
My Test Pattern Generator:
github.com/misterblack1/c64-t...
--- Tools
Deoxit D5:
amzn.to/2VvOKy1
store.caig.com/s.nl/it.A/id.16...
Jonard Tools EX-2 Chip Extractor:
amzn.to/2VazxDS
www.jonard.com/Products/EX-2-...
Wiha Chip Lifter:
amzn.to/3a9ftWw
www.wihatools.com/precision-c...
O-Ring Pick Set: (I use these to lift chips off boards)
amzn.to/3a9x54J
Elenco Electronics LP-560 Logic Probe:
amzn.to/2VrT5lW
Hakko FR301 Desoldering Iron:
amzn.to/2ye6xC0
Rigol DS1054Z Four Channel Oscilloscope:
www.rigolna.com/products/digi...
Head Worn Magnifying Goggles / Dual Lens Flip-In Head Magnifier:
amzn.to/3adRbuy
TL866II Plus Chip Tester and EPROM programmer: (The MiniPro)
amzn.to/2wG4tlP
www.aliexpress.com/item/33000...
TS100 Soldering Iron:
amzn.to/2K36dJ5
www.ebay.com/itm/TS100-65W-MI...
EEVBlog 121GW Multimeter:
www.eevblog.com/product/121gw/
DSLogic Basic Logic Analyzer:
amzn.to/2RDSDQw
www.ebay.com/itm/USB-Logic-DS...
Magnetic Screw Holder:
amzn.to/3b8LOhG
www.harborfreight.com/4-inch-...
Universal ZIP sockets: (clones, used on my ZIF-64 test machine)
www.ebay.com/itm/14-16-18-20-...
RetroTink 2X Upconverter: (to hook up something like a C64 to HDMI)
www.retrotink.com/
Plato (Clone) Side Cutters: (order five)
www.ebay.com/itm/1-2-5-10PCS-...
Heat Sinks:
www.aliexpress.com/item/32537...
Little squeezy bottles: (available elsewhere too)
amzn.to/3b8LOOI
--- Links
My GitHub repository:
github.com/misterblack1?tab=r...
Commodore Computer Club / Vancouver, WA - Portland, OR - PDX Commodore Users Group
www.commodorecomputerclub.com/
--- C64 Stuff
JaffyDOS:
blog.worldofjani.com/?p=3544
C64 Test Harness I use:
• Building a Commodore 6...
C64 Homebrew cartridge PCB: (used for the DeadTest / Diag Cart I use)
www.ebay.com/itm/Commodore-64...
--- Instructional videos
My video on damage-free chip removal:
• How to remove chips wi...
--- Music
Intro music by:
Nathan Divino
@itsnathandivino 
Наука
Several people have asked if these fixes address the jail bars in the C128. They definitely don't. The jailbars come from the VIC-II itself and the problem is especially bad on the C128. I did look at my 128 last night and opened the modulator. It's already sharp so needs no mods there. The NTSC version has color smearing but you can't just bypass the L1 inductor otherwise it lowers the color level too much. (It does fix the smearing though.) So for now, just run a wire to the RCA jack to convert it to composite if you want to work on the C128. :-)
Seems like, to fix that, you'd have to tweak the signal at the VIC-II itself. Don't know if that's even possible.
I would love to see a fix for the checkered pattern in my C64's S-Video signal.
Hi Adrian, it's good to see my old PAL C64 out and about again. I actually bought myself a PAL C64C from eBay now to replace it. But i didn't get any video cable to plug it into anything. I ordered a c64 video to SCART cable a while back but it never got dispatched due to the COVID-19 lockdown (still hasn't). So i just watched this and now 20 minutes later i've converted the RF output to composite. Works like a charm! But i do notice jail bars on the composite output on this C64C. Not sure if this is a similar issue to the one described on the C128. For reference the sticker on the modulator says "P/N: 251916-03A" & "1829F" written underneath in bold.
@HalfSpeedMastering Yep - I'm also here to mention the possibility of adding a Schmitt Trigger to the output of the old VIC-II to clean up the signal :)
I cleaned up the pins of the vic chip (and the socket) and saw a great improvement, though it wasn't gone. I also have a hunch the oscillator is aging.
L1 and C3 are in series which forms a band pass circuit. I am assuming that C3 is not being used exclusively as a DC blocker for Q3. Most likely the resonant frequency is 3.58 MHz, which is the center frequency of the color DSB (double side band) sub-carrier. It was probably placed there to make the RF output NTSC compliant to meet FCC regulations. In a compliant NTSC signal, color bandwidth is less than half that of the luma. This was done to help reduce dot patterns when watching the RF output on a B/W TV and to eliminate adjacent channel interference. Combined, the Y (luma) and C (Chroma) need to fit inside the 6 MHz window to meet FCC requirements. By eliminating the choke, you are allowing the chroma signal to have as much "sharpness" as the luma. So it must be there for regulatory purposes. This will make the composite and the RF output look great, but I bet if you used an old B/W TV you would see dots in the colored areas. I used to use a B/W TV growing up in high school for my Atari 800, so there were people that used B/W TV's. Money was tight... LOL
Spot on reply - you nailed it. Cross channel interference in the analogue tv days would have been a big no-no, in the crowded (and strictly regulated) RF spectrum.
@@Petertronic I realized after I posted my comment that "most" commodore 64 RF installations would be closed - The TV would only be connected to the C64 with no other channels present via the RF TV/GAME switch. If you were to mix / combine the output of the modified C64 with other channels, like various city information channels used to do, there would be severe interference. I set one up a long time ago and had to purchase really expensive filters to make it work.
@@Craig1967 Adrian wasn't interested in the RF output, but I wonder if removing the BP filter might result in bleed into the audio subcarrier too. That might result in hissy audio from the TV used on the RF output.
Came here to say the same thing: FCC Compliance.
You are most likely right, question is: Why is a bandpass- filter required for NTSC and not for PAL? Could it be the larger distance between channels of n n the UHF spectrum (8MHz in W.Europe)?
Further, rather than kill the filter, would it be possible to improve it to have a sharp cut-off at exactly the right frequency? (A standard value of 22mH sounds like a rough approximation.)
I tried it on a PAL longboard with MD6-UE3603 modulator and it definitely made a difference. Cool!
Fantastic video. One of your most interesting ones yet.This was a much needed modification and I really like the way you explain the circuitry theory. Learning a lot from you!
I think this might be my favorite video of yours, Adrian. Well done.
Adrian deserves WAY more subscribers! Such quality content.
I agree
L1 and C3 in the chroma circuit form an L/C “tank” circuit. You can tell this, because they’ll either both be in series with the signal path (as here), or they’ll both be in parallel across the signal path, with one end tied to ground or a supply rail. From basic electronics, we know that inductors pass DC, and capacitors pass AC. In series like this, we therefore know that DC (and low frequencies) will be blocked, and high frequencies will be blocked by the inductor, so our response curve (Bode plot) has to have minima at DC and high frequencies. Therefore, there must be some frequency that maximizes the signal flow, so this is a band-pass filter. This is followed by a similar low-pass filter composed of C4 and R4 to the one we saw with Q1/Q2 above. This likely attenuates the frequencies on the high side of the pass-band, resulting in an asymmetrical response curve, though it might attenuate on the low-side of the pass-band.
I took the plunge and did this today. I've had this Rev 250407 for 37 years. It made quite a difference. Great research and excellent explanation of this fix! Bravo.
I always enjoy that intro. I’ll open my PAL C64 and check which modulator it has. Fantastic video; thanks for all your hard work.
Brilliant! It's good to have this issue covered in a single video. The other guides, scattered around are either vague and/or incomplete.
That was excellent! Really appreciate the all the well explained information. Will be doing this soon. Thank You, Adrian!
I just came across this video, as well as part 1. This is a fantastic mod. Simple but effective. Thanks for all the effort you make creating this for everyone. 🙏
After watching several of your videos, I decided to try out some repairs/mods myself. I have bought a non-working C64 to repair and restore, now I just have to wait for parts. Thanks!
Great timing. I just finished soldering the same exact rf modulator bypass board that you showed in the beginning of the video. Oh well, I guess I'll try this mod first and then experiment further with the replacement board to see if it makes any difference. Thumbs up for going through the PAL version too for us here on the other side of the pond.
I just modded my PAL version with MD6-UE3603 - definitely a visible improvement! I also added the Comp. Out removing the RF out link but instead of soldering directly the wire to the right side connector pin and "smearing it" I soldered onto the 140 Ohm resistor leg directly above it (around 2cms) just in front of the 2 Caps - it's easy to locate the leg using a multimeter. Cheers!
Very well done video, Adrian. And thanks for pointing out the quick jump links in your comments, as I may very well come back to this when/if I mod my machines.
That was a great video. Those are simple fixes that have some dramatic results thanks Adrian.
Great video Adrian, I have the MD6-UE3603 PAL modulator on my 250407 board too and I found chopping out that cap improved the sharpness of my video out very nicely!
Thanks for the wizardry! I like this kind of well explained, in-depth look of schematics and components. Congrats!
Just amazing work.
I wrote a couple questions in the comments but had to delete both, all answers were in the video.
Amazing, thanks for sharing.
Adrian, the mods you're doing here are common in the Atari 8-bit world for the XL machines. They have much worse video output than C64's do out of the box, and they even recommend installing a switch to disable composite video to help the luma-to-chroma leakage in s-video. I'm so glad you've done the legwork to finally bring similar mods to the C64. I did your capacitor clip and inductor bypass to my 250407 tonight and the improvement is outstanding. This is an excellent video!
I'm sure that those capacitors and one inductor you removed to get better sharpness were mainly there for FCC type acceptance. The filter was probably for limiting the bandwidth for NTSC to insure the signal fits inside a standard TV channel.
You are probably totally right -- likely had more to do with the RF signal than anything else.
The caps almost certainly had to do with FCC acceptance, but it may be worth noting that computer RF modules are absolutely terrible at keeping their output within a single channel, and are only suitable for uses where they're the only thing feeding an RF cable. Even if one wants to hook a computer or video game system up to an RF TV, one will get a better picture feeding S-video into a a 2000s-era video switchbox with a built-in RF modulator than one would get by using the built-in RF connection.
Just tried this on my PAL C64 with UE3603 RF Modulator, the difference is amazing, text is so much clearer!
What an incredible improvement. Now I wish I had known to do this back when I bought my original C64.
Hey Adrian, one issue with cutting the LPF caps and shorting the inductor. The reason they are there is because transistors don't act well when they receive signal that has power above the transistor's bandwidth. So if your transistor goes up to 1MHz at unity, and you put 2 MHz into it, you can get ringing or even oscillation, and reduction of dynamic range - the parasitic oscillation will eat into the total (Vpp) dynamic range that it shares with the desired signal. So what you want is: 1. a transistor that can manage the bandwidth you need for your signal and 2. an lpf filter that will filter out everything above, and leave everything below. I bet the commodore factory subbed in cheaper transistors that didn't quite manage full video bw, and that's why they added the severe lpf. You want to check the GBW of the transistors in there, and then replace with something better if necessary. However! bear in mind in general in electronics mfr companies those parts would get replaced for the cheapest part weekly, so what you test will be different to what others have. So it's best to just find a good substitution and use that. Then, build an lpf around it that passes the right bandwidth. you want to check by using an RF signal generator, to see what freqs get passed. Just a guess, but i think you want -3 dB at the top freq your signal is supposed to carry. I think you can just go by LC and RC low pass filter equations to figure out the capacitor values - or just use a few values and experiment, probably simpler. You might take the inductors and just unwind them a bit. But if you completely remove the lpf, you're asking for trouble :-) Hope this helps. Enjoy!
I think that's not an issue here, we are dealing with 4-6MHz max, I bet those transistors can handle up to 100MHz or multiples of that. But shorting the inductor is not fine, because it is there to filter out luma signal from the input of the chroma buffer. I'm surprised that shorting it seemingly has no negative effects. I agree, probably reducing the inductance would be more elegant. Maybe it's enough to put a ferrite bead on the place of it. The original 22uH probably delays the chroma signal too much, causing color smearing.
Very nice! I only clipped the capacitors and it did wonders for my C64's picture. Thanks for sharing this!
I've now modded my PAL C64 (but I went the extra hassle and removed the modulator to be able to remove the cap from behind!) and indeed picture quality has improved! Thanks a lot!
This is one of the single best video videos I've ever seen. Going to mod my C64 and SX64
No idea why I've watched this, but it was fascinating!
Very neat explanations, nice filmmaking too, thanks you.
Tried this on my MD6-VA3405, worked perfectly. Thanks Adrian!
Thanks a million Adrian !
I was looking for a way to improve my 250407 pal board picture quality on my crt monitor and it improved so much ! I am very grateful THANKS !!
Although this video was released a while ago, I didn't want to do the mod until I educated myself enough to understand what's actually going on here. Over the last couple years I spend hundreds of hours working on these computers and finally understand now what you're trying to do. I did the full 4-change mod on the 3403 and the picture is much clearer and sharper than it was before. For years, I blamed it on the digital conversions that occur when displayed on a modern monitor. The RF to Composite mod is pretty handy too, since most people don't have an RF compatible TV around anymore... Regarding the 3405 RF Modulator, bypassing/removing the inductor does also make the image clearer. Excellent work Adrian and Thank You!
That's the fastest mod I've ever seen. Holy smokes, this is game-changing wizardry!
Thanks for sharing! I hoped there was a way to make the output better without drastic changes (like removing the whole modulator). Now I know what I can try to improve video output. Great stuff! :-)
Just cut the cap on my PAL 250407. Even on the main basic screen I was blown away by the difference. Thanks a lot Adrian.
Wow, that was a lot of good information Thanks Adrian!
Thanks for the amazing video. Great to see someone spending a lot of time to get a perfect result. Amazing quality at 25:30 and (monchrome) at 27:05. Keep it up!
Awesome work! I'm going to have a closer look at the modulators in my different PAL machines to try to figure out what's going on.
But yeah as has been noted by others, the smoothing of hanover bars gives us using PAL machines a vastly increased palette. So I think it's more of a feature tbh :)
Awesome work Adrian! Thank you so much for releasing the source code too - perfect :)
Thank you Adrian for a simple fix too clean up the svideo signal.
I just performed this on my PAL model ASSY NO 250407 - with VIC 6569R1 1183
video looks much better as you showed.
Keep up the videos, I love all your content, how you transfer your knowledge to us all and presenting style.
This is great, thanks Adrian. I just wheeled out my C64 two use in a nerd project, I used it as a twitter client 7 years ago but thought I create a little Weather BASIC program pulling from an online API. The video on mine looks quite blurry to my eye on a TV across composite, so I am looking forward to trying out some of your mods.
And did it work, did you see improvement ?
I just watch the whole thing even if I am not able to do the kind of stuff you do because you have a great voice and I find all of this interesting and I need background noise on graveyard shifts.
I do have some electronics projects I've been meaning to get to but I've been more of a software guy than hardware guy so I don't have much confidance in my soldiering ability etc.
I'm glad I found you (I come via 8 bit show and tell some weeks back) but I also do follow 8bit guy as well.
This is amazing! I installed
Perifractic's VIC-II² PAL/NTSC Switcher Kit in my main C64 and I was getting really bad color smear on the PAL side (it was originally an NTSC machine). With the inductor bridged in the MD6-VA3405 modulator the PAL output is now fantastic. Unbelievable difference considering how much smear I was getting!
I'm about to install a VIC-II² PAL/NTSC Switcher Kit in my main C64, an original NTSC one like yours, so that's great information to know. Did you install the Lumafix components? I've left mine off for now and thought I'd see how it looks on my setup.
@@Ikrananka I did install the Lumafix components. It helped with the jailbars as you'd expect once adjusted, but obviously did nothing for the color smearing issue.
Regarding Hanover bars - PAL works by inverting the phase of a portion of the colour carrier every other line. The idea is to eliminate hue errors that occur in NTSC. PAL receivers don't have a hue control for this reason. Unfortunately, to invert the colour carrier accurately, with no phase errors, is quite a difficult to achieve. These phase errors would normally be canceled out in the receiver with the delay line - at the expense of vertical colour resolution - but without that, you'll see the slight hue errors.
It's probably totally a non issue for normal video especially as you sit across the room, but sitting close to a computer display with solid colors, it really looks disturbing. (to someone who isn't used to it)
@@adriansdigitalbasement That's exactly it. The first PAL receivers in the 1960's used the PAL-S standard, S for 'simple', which didn't use a delay line for cost reasons and relied on the human eye to average out the colours.
On a related topic; I wonder if the ZX Spectrum has any problems with Hanover bars. The ULA in the system outputs unmodulated video which is converted to PAL externally. However, the colour carrier isn't inverted, the baseband video is inverted on the ULA's output. This makes the colour modulator simpler. It shouldn't have the phase issues I mentioned because the colour carrier should be the same phase every line.
@@256byteram the main problem with the spectrum is the dot crawl caused by using two separate oscillators. They fixed this in the later 128 design by 1) having the ULA generate RGB output and 2) clocking everything from a single 17.7345MHz oscillator.
I was thinking he should make a better RF module replacement board, but the fixes he then shows are really easy to do. Good stuff.
There are a few pcb designs out there for replacing the rf modulator including the one he tried. It worked, he just didn't see the need to make that vs just doing a few minor mods on the existing one. He could make his own pcb variation but I'm not sure there's a need out there for another option. This was something that wasn't out there and that anyone can do.
Did this to my 250407 with the MD6-VA3403. Looks great on my 1702 monitor. Simple composite output is a bonus also. Thanks Adrian!
Just a warning to anyone trying this: If you prefer the softer output do not do this! Perhaps just bypass the inductor and don't cut the caps.
Just modded my (entirely stock) 250407 with MD6-VA3404. Looks fantastic! RF can now proudly claims to have Adrian's Digital Basement 2020 mods applied.
Thanks for your work on this Adrian!
Thank you for existing in this video space.
My PAL 250425 has a RF-modulator called "251025-05", and it also has another label reading "5095". It's not like any of the ones shown in the video, and features a big metal can (inductor?) in the middle which has its screen soldered to the lid. Having a closer look inside is therefore impossible without a soldering iron at hand. Another detail, instead of a channel switch, it has a trimming-screw in its place.
love this series...has encouraged me to repair my pile of acorn electrons...about 2 dozen working...3 still to repair...2x pres plus 1 outstanding
You absolutely can -- and I think it lets you launch both copies at the same time.
Fascinating topic Adrian. Thanks.
Great lighting Adrian!
Another excellent and detailed video Adrian. I'm not a C64 owner, but I still enjoy each one of your videos.
With my ex-radio engineers hat on, I wonder if the issues with the RF modulators is because they were just bought in modules that might be generally used in say analogue video recorders where their deficiencies are not so noticeable with moving pictures compared to still images like the ones you were showing. Just a guess. May search on the part numbers to see what else they are used in.
Thanks again for this great video, might going to mod my c64 in the future.
Thanks for the bookmark links (even though I always watch 100% of your excellent videos anyway) and other links in your show notes. You should also put an obvious link to the previous part(s) of a continuation video at the top of the show notes.
Thanks!
Although this kind of work is not my thing at all (and to be honnest i never tried/bothered to do stuff like this) I do find it very interresting! a Thumbs Up for you Adrian! :-)
That's funny, I actually noticed I got a color image from my pal c64 on the Luma pin yesterday. And was quite puzzled about it. But your comments around 27.45 explains it! Thanks
I'm never going to any of this stuff but find it incredibly fascinating to watch
Thank you soo much, this was extremely helpful
PAL viewer here! After seeing the unknown modulators for PAL machines, I dissassembled my C64s to check them. I don't have the proper cables to see the video output, so I'll just confirm the model numbers.
Here's what I got: OG C64 250425 board, Mitsumi MD6-UE3605 modulator; C64C 250466 board, Commodore 51A1-10 Rev. 2 modulator. On my machines the model number wasn't on the steel can, but printed directly on the PCB.
That was a lot to digest, hoping to incorporate some of the changes when I can get back to fiddling with it 😀
Pal? If its 3603 it was done in a few minutes. See from 27:15
Awesome job, Thanks Adrian
It's been forever since I've done analog electronics but L1/C3 looks like a classic bandpass filter. The combination is filtering out frequencies below and above a certain range. Probably intended to clean up noise before amplifying the signal.
In Hannover they just call them bars 🙂
LOL
I used to service TV's in the UK. Hanover bars are almost never seen. Only ancient early 70's tv's or very cheap tv's would exhibit them. 99.9% of TV/monitors from the 80's onwards used PAL decoder IC's (with delay line) that accurately deal with and correct the alternate line phase errors and they cannot be seen. If they are showing up on a signal that's going into a converter box, that converter is going back to the 70's by taking shortcuts : i.e. not bothering to do the phase detection and correction properly (which requires some considerable DSP processing by the way).
Thanks for this video, finally getting around to doing this mod myself to get composite out without the cable. I'd love to see you do a video making the vic-20 32k memory expansion at some point. :D
Hey Adrian I did these mods to my c64 I recently got from my uncle it was his's when he was a kid and passed it to me (still in shock wasn't expecting that). anyway holy cow these mod made a night and day difference. was super easy to do which is always a plus. Oh my board is a 250407 "Rev. A-CR"
I can confirm that my PAL 250466s have a MD6-UE3605. PAL 466 boards generally have the best video quality.
Great video. Really informative.
Best simple C64 mod ever.... why didn't somebody figure this out 35 years ago? I did not add the 100nf cap, as it was a bit tight for my soldering iron and skills. The image is much sharper, and the reduction in color bleed is very apparent. Thanks again for these mods.
I did the 100nf cap, just because i was there anyway, but I'm not sure there's a need. As for why they didn't do it 35 years ago, good question.. There have been composite replacements, maybe anyone who has the skill, opted to make and sell those instead of simple DIY options.
Yeah I have to wonder why no one figured this out at some point between then and now too! But I'm glad people are benefitting!
Thank you so much for this information as a new owner of a c64 ill be performing these mods.
Great content Adrian. Thanks a lot.
I love seeing u agin and again, specially in this time
@I Blow Bubbles hahahaha
@I Blow Bubbles Love might be too strong a word :)
Great video. I did this mod to one of my C64s with great results, similar to yours. I also tried to do something similar to one of the early 1982 motherboards (326298 Rev A) that don't have the the chroma output. On those motherboards, the video out does not go through the RF modulator. I lifted some of the filter caps in in the video circuit, which improved the sharpness somewhat, but the overall video output still looks pretty bad. It 's probably due to the older ceramic VIC II chip. I'll try swapping in a newer chip later this week when I have some more time.
The 326298 generates the composite video on the main board instead of in the modulator. No mods need to be done on the modulator. Remove C73 to increase sharpness. It makes a big difference. Check the value of R10. If it's 300 ohms, replace it with a 120 ohm resistor or parallel it with a 220 ohm resistor. That will increase the brightness. C73 and R10 are inside the RF shield near the VIC chip. While you have the case open, check the value of C10 and C11. They are the filter capacitors for the SID. If they are 2.2nf, replace them with 470pf. That will improve the audio.
Great Finding's , Thank You for your Experiments.
Great vid, I always knew PAL decoders had a delay line in there, but I never found out what it did, till now.
I assumed it was for the decoder to be able to somehow mix the alternating phase's to find an average?, but not to purposly reduce the vertical chroma resolution.
I did the mod on a PAL MD6-UE3603 modulator, this modulator has been taken from a 250407 board and used on a new SixtyClone board which I built myself. I am feeding the signal through a RetroTink X2 and the output was a bit blurry. Not too bad, though. After this mod, I can definitely see a difference in the sharpness. It is a lot less blurry. Thanks for this tip!
Thank you - Worked like a charm on my ....407 mainboard.
I run svideo (YC) only. 250407 ntsc breadbin. VICII2. I did this mod and it’s good all around (NTSC & PAL) on both my HP 4:3 elite display port medical document viewing monitor and Sony PVM. Side note: yes, the VICII2 does fit with SIDFX on this board. Even had room for mechboard64 and FU32 dual tetrode vacuum valve headphone preamp and heat sinks all around. Considering cramming an OLED audio spectrum analyzer in as well.
I was thinking of hitting up ebay for a 3rd party rf modulator but having seen this video I will just mod the one I have. Thanks
excellent. this gives me really hope. I had my pal rf modulator replaced by a newer 1 that was actually a terrible commodore version. so i'm going to mod my original pal and put that back and see if that gives a sharper picture.
small update. I applied the mod on my PAL RF modulator by cutting off the capacitor C9, the result i still blurry and color smearing. I still have to use the lumafix64 to get ritt of the stripes. results are the same on both my VICII 6569R3 and 6569R5. any help would be great. I'm still using the DIN video connector to red/white/yellow cable.
Adrian thank youfor the video! You might want to clean that RCA connctor at 4:50 :-) Keep up the great content!
Watching this while writing modifications to Mister C64 looking for inspiration for how to simulatewhat you are trying to fix :)
D1 and D2 are for biasing the transistors, otherwise they would be completely off at the bottom of the waveform during sync pulses. The capacitors and inductor you've removed are most likely for EMI suppression (FCC compliance).
I like these circuits with analog tricks, today we tend to use chips for everything, it is useful to see how you achieve stuff with simple transistors.
They also partially compensate the Vbe drop, so the circuit provide a better buffering.
Removing EMI related stuff? That's Adrian's middle name!
L1 - C3 is a band-pass filter, likely for the 2 MHz chroma band, which has a carrier at 3.579 MHz above the luma carrier. C4 would be a low-pass filter.. the only thing above the chroma is the FM audo band though... it may be needed to prevent the transistor from oscillating at a higher frequency, usually a good practice in designing HF circuits to damp the input that way.
By cutting the inductor out, the circuit is changed from a band-pass filter to a low-pass filter with a -3 dB point relative the the base resistor R4. You may get some additional noise coming in from the main PCB (digital logic noise) but it does not seem to affect the signal so it seems ok...
I think some considerations were put in the design of the circuit to meet FCC emissions guidelines for NTSC signalling... not really relative anymore...
Cheers,
The coil, capacitors and resistor in the chroma input form a tuned circuit that was probably designed to resonate at the color carrier frequency. So if you bridge the inductor you also inadvertently reduce the color signal.
Adrian, love the channel, but stop looking at yourself in the monitor! lol. Seriously though, viewers want to feel as though you're talking to them directly. When you look straight into the camera lens, you accomplish this. When we see you looking at yourself instead of us we're not as engaged as we could be. Not engaged means not invested. I understand that you just want to make sure you remain in frame the whole shot through. I also understand that it can be difficult for some to get into the habit of looking into the lens and not the monitor. Trust me, I've been in video production a long time. It may seem like a tiny thing but it matters to viewers more than you think.
You're a great presenter. Best of luck in the future! Glad to see the channel growing and getting some much deserved love. :)
I promptly went down stairs and did this mod to my 250407 board. The quality has improved, but it seems like when using the s-video the checkerboard pattern and jail bars seem more pronounced, it may just be all in my head though. I didn't take a before and after pictures so I cant be sure. The old LCD TV I'm using doesn't have the best picture quality, but its the only thing I have with s-video.
This is definitely a worth while mod that doesn't cost anything but a little bit of time, I wish this knowledge was around back in the day.
Tons of useful information even for non-Commodore tinkerers!
Now that I've seen the schematics of the modulators, I have an idea:
I had noticed once, that when I connected the chroma output to my TV's composite input I get a picture. Not worse than using the real composite output.
My theory is, that the color smearing/fringing on these larger contrast areas might be due to the luma signal passing back through the capacitors C6/C7 on the NTSC modulator into the chroma output. (C11/12 on the PAL version)
I haven't tested it, but if you intend to use S-Video only, you might try cutting those two capacitors out. Or, if you want to keep the color composite output, you could add a fast Schottky diode in series with each of these two capacitors.
Wow that is some serious backfeeding of luma and sync into the Chroma! I've never seen that work on any of my machines before. Yeah S-Video only it likely would improve quality if you break the connection like it did on my little bypass board. Since I don't really have any PAL machines to play with I can say for sure.
Just did my 407 with the UE3603, deffo better, shame its one that suffers from the rise and fall issue. So a huge thank you for doing this tutorial
Yeah Mr Lurch did some testing for me and he had one PAL VIC that was also really soft and another that is better ... On the soft one, the improvement was minor as it was for me.
@@adriansdigitalbasement Its better so I'm more than happy, thanks Adrian..
A quick and simple fix... 40 minutes long - I love it)))
Be pulling mine apart tomorrow!
I speculate that the R1 sharpness issue on PAL has to do with too big of a loading capacitor on the Luma output of the VIC-II chip.
Hi Adrian, thanks for great video.
The most interesting video about C64 color problems! But I would like to ask you where can you find the 'yellow PCB' placed on top of the TEBL PCB? Thanks so much for an answer ...
So interesting they made the circuit like they did, Commodore was all about saving costs so not having more components (which actually make the signal worse), seems the right choice from the start. Which makes me wonder if it's actually, in certain situations, "dangerous" or a disadvantage?
No questions, just want to say I love your vids.
The Hanover bars are created due to the nature of PAL fixing the NTSC tint issue by alternating the phase of the chroma signal per line. That's what PAL stands for: Phase Alternating Line. This has the effect that phase changes are cancelled out so the tint of the colors is stable. But at the cost at those artifacts. The proper way to eliminate these is not to average the colors between the two lines, but to use a comb filter. SECAM by the way has half the vertical chroma resolution because it actually uses a delay line for the chroma signal as it is transmitted every even (or odd, not sure) line. That's why it's called "Sequential Color And Memory".
The quality loss with half resolution chroma is the same as in digital video 4:2:2 (with chroma information each line) and 4:2:0 (with chroma information every odd line).