-^CrossBow^-
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Posts posted by -^CrossBow^-
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14 minutes ago, NISMOPC said:So, here are some pics. The 6.8k is inline on the wire coming from R6 under heat shrink. R5 is connected to R6 after the resistor and then both go to audio in on small board.
So if I'm reading this right, you have a 6k8 from both R5 and R6? Because if you were take the signal after R5 closest to the rear of the console, then you wouldn't get any pokey at that point. Both of the audio inputs route from the bottom of the resistors up to the poly caps and then into the RF modulator section.
Eitherway, with only 6k8 off the TIA that is half of what the original circuit was using to keep the volume on it down next to the pokey. Granted it isn't nearly as bad as just taking the audio from before they hit the resistors as that is nothing but pure TIA driving the signal at that point but still.
I actually use mil spec 1% resistors in the 7800 services I do. You have to read them though because they don't have color bands and are just brown colored resistor pills with their values printed on the sides.
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2 hours ago, youxia said:I don't think bandwith will matter much since [email protected] is not something that I see happening on consoles (nor PCs for any time soon), outside some simpler titles.
Lack of VRR is much more worrying. I do my AAA gaming on a PC these days and can't imagine not being able to use adaptive sync.
I don't know...I've been stuck at 60hz only since forever and it doesn't bother me any. Then again, I don't play competitive online games either and only play the single player campaigns on FPS type games. As long as I'm getting my 60fps I'm good.
But then again, I come from the generation where getting anything over 20Fps on Quake II was considered excellent when it was first released.
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The reason is that if you don't have the resistors in place, you will get unbalanced audio volume between the TIA and POKEY audio. Taking it from the bottom of the resistors especially R5 means that you are taking the audio before the resistors and will result in the TIA audio overpowering the POKEY. When I do these kinds of installs, I clip the legs of R5 and R6 facing the rear of the console and then tie the legs together with a 10µf cap off the tied leads out to the audio jacks.
If you leave the RF modulator in place and want it to work fully, then I actually solder in a second 6k8 and 18k resistors from the bottom legs of R5 and R6 and then tie the leads of the new resistors together followed by the filtering cap.
Also to answer your last question. If you only have a 6k8 off of R6 and nothing from the POKEY, you will still have the TIA being louder in volume as compared to the Pokey. In a game like Ballblazer you won't notice this because that game only uses Pokey. But in Commando or another game that uses both, you will notice that the volume of the TIA sounds are much louder than the pokey. If that doesn't bother you then I guess your fine. But for most, it drowns out the pokey to the point where it is hard to hear the background melodies etc. that the pokey is providing.
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Well, I've not used the official cables, but I did buy a set of the generic TOMEE branded cables a few years back. The results were aweful checkerboarding in the red hues. I've seen it before on cheap cables and since these cables had both composite and s-video outputs I had a sneaking feeling on something.
Taking the cable connector apart where it plugs into the DC my fears were confirmed. The TOMEE cable was splitting the composite signal to the chroma on the s-video output! While that does technically work, it results in a non pure chroma signal and isn't the proper way to do it.
Well the wires in the cable only allowed for either composite or s-video to exist so I cut the composite off and rewired the composite lead on the plug to the actual chroma output pin from the DC. That resulted in a really good s-video picture that I used as my main until finally installing the DCDigtal into it and going fully HDMI.
So my point is to be aware of the cheaper cables because they are likely doing something similar and if you want to be sure to get the proper results, I would stick with the Sega branded ones or be prepared to have to modify the cable you get if you go 3rd party. Granted the TOMEE branded one is the only other one I've used and I also have one of thier VGA cables and that actually worked really well, but yeah just something to be aware of.
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5 minutes ago, Andrew Davie said:
Just be curious if you had another PAL TIA on hand to swap it out with, if you still had the same issue?
We know that different TIAs are out there and that later ones especially have issues. But you have what looks to be an early '81 produced TIA so I wouldn't think it would be a troublesome TIA.
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Is this composite and audio only or? I'm asking because while it isn't quite 8, I do have an old JVC AV selector that has 7-inputs and handles composite and s-video along with audio on each input? 7th input is on the front however. Might be overkill for what you are looking for but I used it for years for my analog composite/s-video systems until I got my Extron.
It is the JVC JX-S700. Here are the specs on it from the JVC support page. Mine is missing both of the front covers and I do not have the remote. That is how I got it years like 10 years ago off ebay. It might be too big for your needs as it is basically the size of an AV audio receiver as it was designed to fit in with the rest of your audio/video stuff at the time.
http://support.jvc.com/consumer/product.jsp?modelId=MODL003020&page=1
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6 minutes ago, DrVenkman said:Remind us, please - what is C64 doing? Is it a filtering cap tying something to ground? Neither of my systems has that cap.
It is part of the extra timing circuit that was added in the later revisions of the 7800 and then removed again, in even later revisions. The cap looks like a resistor but is actually a banded ceramic cap and usually green in color. If present you will find it in the dead center between two small 74x logic ICs in the right hand center side of the board. It seems to only affect the timing of the video since the actual game logic isn't affected by removing this. It is the cause of scrambled screens on most of the bus stuffing demos for the 2600, the cause for some of the activision games to not work etc. But again you can literally boot up a game that doesn't work with it enabled, clip the leg in real time and as soon as you do that the game screen comes up without a reset of the system. Put it back in circuit while up and running, and the game screen will go haywire again.
But to get back ontopic in regards to TIA...
@Andrew Davie, what brand of TIA are you working with here? I just posted something interested in my blog in regards to TIA issues between two different manufactures of TIA in a 7800 I discovered.
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38 minutes ago, SpiceWare said:I don't recall hearing about clipping C64 before. Did a quick search and see you've mentioned it quite a bit, but doesn't appear to have been in a topic I usually follow.
While it doesn't help me, it might help @batari.
Well, what really bakes the noodle on this. Is that you can start up the parrot demo or any of the bus stuffing demos, you usually get scrambled lines on the screen. While that is happening, you can then switch C64 out of circuit, and it will instantly show you the demo without having to reset the console or any thing.
That tells me that the issue is specifically a video output issue and not something on the main logic level of the code? If it were, it would require having to reboot the system after taking C64 out of circuit to get it come up right. You can literally enable/disable C64 while the demo runs to see the effect on and off.
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On 2/2/2021 at 10:17 AM, SpiceWare said:Hardcore. Glad we went the Data Stream route, if we get something wrong we usually still get a screen, just with graphical glitches. The usually because it will fail if the data stream that was wrong was used for flow control, as it contains a list of ROM addresses to jump to.
I have mentioned this before, but I use the old Parrot demo to test bus stuffing on 7800s. Clipping C64 gets that demo and the others working each time. So not sure if that helps?
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I got my order in. This will be the first Lynx game I've bought in a few years now I think?
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4 hours ago, amn said:Thanks for the replies guys! So this is the kit you would recommend?
How easy would this upgrade be for someone who doesn't have a ton of experience with electronics? I'd like to do this myself if possible, but don't want to do anything that I'd have a better than 50% chance of messing up and killing the CV altogether. Also while I'm putting in the order for this, is there anything else you'd recommend me picking up? I'm paying for shipping anyways, may as well make it as worthwhile as possible.
It isn't terribly difficult to do this mod, but even with my equipment I've still had a pad or two just melt away with the rest of the solder when trying to remove the old ram even with my iron only set to about 300C, so you need a temp controlled soldering iron. That is why I recommended the clip the legs method and then remove the legs from the vias off the PCB after. As for other things to get, you might look at getting the ESD protection boards for the joystick ports. And if you don't want to mess with the 10sec delay startup on many games, get the bios update chip too.
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7 hours ago, sramirez2008 said:Parallax worked for me but the rest didn't.
Same here. The Parallax demo works but the other pokey demos just result in the clicking I spoke about before. Except for the Cybernoid450 file. That one just crashes the 7800 when I try to run it. Not sure it is signed with the encryption as I don't believe that one generates the 7800 rainbow logo.
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Well on the previous ones I tried, I would just a clicking noise that was in beat with the music. But it was a single click and not multiples indicating that it was just one voice that I might be hearing something from. All the later made pokey demos like the dual pokey etc. seem to work. And some of the other ones did work but it is hit and miss.
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1 hour ago, fdurso224 said:So true Brat. Those Samsung CRT's are bulletproof. Still have mine after all these years bro. 8^)
Anthony..
I had a late model Samsung Tru-flat HD CRT. It was like a 32inch or something and was heavy as all get out! It had a really good picture but it did suffer from two issues I had with it. The first and most obvious was the convergence issues it had. There was a noticeable bow in the image along the bottom of the screen that I was never able to get sorted. Normal games you didn't notice it much, but when watching the news or anything with a scroller along the bottom, it would stand out.
It wasn't able to handle light gun games.
It had an issue where after a few min of being on, a noticed green and purple spots would form on the screen in the upper left and right corners. I was told this was due to the power supplies in those TVs not being quite adequate. The ONLY way to avoid these color spots was to literally turn the TV around as it was affected by the magnetic fields all around it. It did this at two different houses I lived in while I owned it and was a pain in the ass not being able to use the TV exactly where I wanted to in the house. Also the TV did have a built in degauss coil as you would hear it "grunt" when you first powered on the TV but as it only did it on initial power on, it didn't keep the spots from forming.
Calls to Samsung support weren't helpful as they were the ones that told me to turn the screen to different directions to be rid of the spots. In general, the tru-flat screens just weren't that well regarded from what I would learn later on. It did have all analog inputs of coax, composite, s-video, component and not 1 but 2 HDMI inputs on it as well.
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29 minutes ago, sramirez2008 said:Parallax worked for me but the rest didn't.
Do you just a clicking sound when trying to run them? That is what I got with the other versions released. But I'm not home yet to test these for myself until later.
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Well as an example on the equipment I have. All of my RF consoles are a magnitude darker overall on my Sony LED/LCD in the game room. Some colors completely just aren't there when using RF. It was the main reason I first looked into AV upgrades for my classic consoles. I do have access to a few CRTs and even use a small 9" on my workbench, but for the bulk of my gaming, I wanted a larger display that I could use for both classic and modern systems. The ITC game room is pretty small compared to most so I always knew that trying to have both a decent size CRT and a modern flatpanel for high def stuff wasn't going to be possible.
But as has been mentioned, with a UAV in place, I don't have these issues any longer through my setup and can keep the TV at a setting that works for all consoles at this point.
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1 hour ago, john_q_atari said:It's awesome that you included an interior photo post modifications when you worked on my 7800 a few years ago. I was able to search my email, see the photo, and see what appears to be a nice analog voltage regulator bolted to a huge (factory original I am assuming) heatsink so I guess I am good to go whenever the time comes for me to receive my dragonfly.
I also have all of those pics on hand as well of course. Most of my clients do not opt for the option due to the increased cost so it doesn't effect that many and even if it does, you can still use the original 7800 PSU to power the 7800 and a different PSU to power the DF cart and that will work fine. So It does require using two PSUs to do everything, but then everyone had a PSU for the 7800 already, and they already have to purchase a different one for use with the DF if they haven't one on hand so it isn't that big a deal. Newer versions of the DC-DC regulator I've been installing for over a year now do NOT have issue with the DF cart and work properly.
The DF cart has a lot crammed into that case so it isn't any wonder that is requires power directly to it to begin with.
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If you have cleaned the switch and tried different PSUs with the same issue, then it likely is the vram at this point. The service manual has a few different screen caps of various graphical issues that point to which ram module I believe. The more long term solution is to replace all of the vram with the +5 ram upgrade kit. But the traces on the CV, especially in that area are more prone to lifting than other parts. So if you do upgrade the vram, I would advise use of the clipping of the legs method and then using your soldering iron and tweezers etc. to lift the remainder of the legs out of the vias and go from there.
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9 hours ago, CPUWIZ said:Need to check if it outputs a steady 9V (why 9V?).
Because the hardware inside is only rated to take 9v max input from what Rafal advised me. That is why it needs to be a switching psu to ensure it is only kicking out 9v as anything over is likely to cause heatbuild up in the DF cart. This was also the reason why older 7800s I put DC-DC regulators into don't work with the power passthru from the DF cart. As the PSU on the DF is only 9v, it is only passing 9v to the 7800. But the DC-DC regulators I was using back then actually didn't kick in to +5 output mode properly unless the input voltage was more like 12v. Normal 7800 PSUs and other transformer PSUs put out over 12v without a load.
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8 minutes ago, Trebor said:Agreed. Under a CRT bullets are perfectly visible...
...ditto with Berzerk/Frenzy.
Issue here is a modern display and how well/poorly it (and other involved components) upscales and what kind of signal it is receiving as source.
For instance, a 7800 output from a UAV video mod via S-Video is perfectly visible as well. I can vouch for that to my Samsung 4K.
RF/Composite though straight to a modern HD display or via a converter (and the quality thereof in itself and managing the source signal), may not perform nearly as well.
Arguments can be made both ways regarding stock and intended target hardware. Certainly, any accommodation that can be made, Bob, would be wonderful. At the same time though, supporting both your vision for this game and everyone's setup display configuration may be a bit much, if even possible, to achieve an idealistic appearance of everything in the game.
Was going to say I've seen this on modern displays but only through the RF side of things. Also the display itself matters as those with higher refresh panels will not have as much blur on motion as others. I could be wrong, but I know that Bob has an older AV mod in his personal 7800 for testing things so it is possible he isn't using RF output anymore to know about this being an issue or not.
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23 minutes ago, Eagle said:@-^CrossBow^- could you send me one of not working pokey demos? I would like to have look in code.
These are two right off hand I know aren't working. This was after they had the NTSC encryption added to them so they would at least try and load up. They do but again I just clicks in time with the tune that should be playing. And this was happening on the 3 consoles I tested at the time.
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6 hours ago, juansolo said:I don't want to make this sound like there's a load of issues, becuase there aren't, and it's likely down to console variance (which there appears to be a lot of in the PAL 7800 world). It's a bloody brilliant thing. Loving it, RJ has done an outstanding job.
There are at least as many and possible more variants on the NTSC front as well. Case in point is that I can't get most of the Pokey music demos to work on any of mine and only get some odd clicking in beat with the music. While other pokey demos, especially the newer released ones, seem to work fine. I've not tested BB but have tested commando and that game worked as expected and was the game that made me realize that my pokeymax on the DF was actually too loud compared to the TIA.
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14 hours ago, DrVenkman said:This kind of thing just gives me more incentive to replace that proprietary jack on my daily-driver 7800 with a common 5.5/2.1 barrel jack. That stupid POS decision by GCC/Atari has given far too many owners headaches when those bullshit OG power adapters die, probably because of a break in those tiny little conductors they chose for the wires.
I actually think Atari may have done it on purpose to prevent consumers from using the wrong PSU with the 7800 because they weren't paying attention. Think about how the issue with the 5200 adapter and 8-bit drives? Or someone thinking they can use an NES adapter in something because it fits? I'm more shocked that Atari decided to use a common barrel jack on the Jaguar but then they also designed it so it could use the same thing a Genesis/SMS/TG-16 could use and by then, the SNES was the more likely competition and that uses a totally different power connector.
Anyway, that adapter that CPUWIZ posted will work for those that want to use a Genesis PSU with the DF or have modded their internal power connector on the 7800 with a barrel jack wired for using with a Genesis like PSU using Center - polarity.
Either way you do it, the DF cart is still a fantastic piece of hardware!
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I was playing this lasted build last night through my DF and it really does add that extra touch on the flicker of the exhaust. I know it is just a small thing but I'm glad you thought to include that.
I did have one odd bug occur on the previous build of the game. I captured it on video but it only happened once and I can describe what happened:
It was on the screen with the artifact on W1. I was just about to grab the artifact when the drone moving up and down in front of the gun clipped me on the bottom of the ship as it was moving down. In other words I moved too quickly and hit the top of that drone. However, when I was brought back at my last checkpoint (2 screens to the right and up from that room), I was shocked to see the artifact just floating in space on that screen in roughly the same place it would normally be? I went through the force fields and was able to touch it and pick it up as if it were on the other screen. It was like the artifact was brought over with me when I died, even though I hadn't actually picked it up yet from the previous screen. I completed the W1 demo and the game did acknowledge having found the artifact?
Does that make sense or do I need to find that in my long play capture and up it here?
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7800 Composite Mod question on the 6.8k Pokey
in Atari 7800
Posted
This is a valid point, but I believe the reasons for the resistors in the first place is that the audio without the resistors would be too hot otherwise and the resistors are there to lower the amplitude of the signal. But you are correct in your thinking. If you really wanted to test it, you could do what others usually do with doing this mod. They take the pokey from the top where C10 is (Removing C10 in the process). As that is literally just the first via from the external audio line off the cartridge slot.