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sd cartridge for 7800?

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2 hours ago, batari said:

Hmm, I will investigate that. The card edge connector on Concerto was someone else's work which I trusted was correct. I will take a close look at the pins on my various consoles and see if it could cause any issues. Of course I will bring it into spec for future releases as well. Lesson learned, I should have cracked out the calipers and did all the measurement work myself :(

 

I've seen what the edge connector looks like on the concerto and it is off from spec.

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FYI, here is an image of my used edge connector.  Is it too far to one side?

 

image.thumb.png.e2679bcd6143aaf556b30587e66f8772.png

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3 hours ago, Shawn said:

 

I've seen what the edge connector looks like on the concerto and it is off from spec.

 

33 minutes ago, KylJoy said:

FYI, here is an image of my used edge connector.  Is it too far to one side?

 

Are there any photos show the PCB butted up against one from another cart for comparison? 

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37 minutes ago, KylJoy said:

FYI, here is an image of my used edge connector.  Is it too far to one side?

 

image.thumb.png.e2679bcd6143aaf556b30587e66f8772.png

If the striations from the pins of the 7800's cart slot are any indication, it looks like it might be OK.

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They don't look off to me, but I'm not a micrometer.

 

image.thumb.png.0f55df54b57e0d1d1970b27d2ed63291.png

 

I'm also not a photographer.  Pa-dum-PA!

 

I'm here all week...  Don't forget to tip your waitress...

 

 

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2 hours ago, KylJoy said:

They don't look off to me, but I'm not a micrometer.

 

image.thumb.png.0f55df54b57e0d1d1970b27d2ed63291.png

 

I'm also not a photographer.  Pa-dum-PA!

 

I'm here all week...  Don't forget to tip your waitress...

 

 

That's way close enough for what this is!  There's not a trace on that PCB that's even off by a BCH (technical term - look it up).

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I can see from the picture 7 of the pins are out of alignment starting from the left hand side.. very noticeable.. 

Edited by Jinks

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The picture is just a sample.  In person they do not seem to be out of alignment.  The angle and parallax may be inducing something.

 

Look at the wear pattern on the pins of the Concerto.  Are they showing an alignment issue?

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To the extent theres any visible difference in those at all that’s not due to parallax (which I don’t see, frankly), no consumer system on earth requires that level of mechanical precision to make a couple dozen electrical connections.

 

Furthermore, the wear patterns on the contacts shown in post #1777 are pretty clear indication that that contacts on that Concerto align perfectly with the spring metal contacts of the 7800 cartridge port.

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Agreed. It was worth checking, but unless someone else has a spring wear pattern that shows contact being made significantly off-center on the pads, I think we can move on.

 

Has anybody with the issue tried a cart slot cleaning? As before, just looking for things we can push or pull, until there's a different result.

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2g-7OB.gif

 

FYI, it looks to me that the "off-center" wear pattern on the Concerto match very closely with the "off-center" wear pattern on the Xevious cart.

 

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17 hours ago, KylJoy said:

They don't look off to me, but I'm not a micrometer.

 

image.thumb.png.0f55df54b57e0d1d1970b27d2ed63291.png

 

I'm also not a photographer.  Pa-dum-PA!

 

I'm here all week...  Don't forget to tip your waitress...

 

 

Hey - that concerto board looks familiar!

 

Wonder where I've see it before? 😆

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27 minutes ago, KylJoy said:

FYI, it looks to me that the "off-center" wear pattern on the Concerto match very closely with the "off-center" wear pattern on the Xevious cart.

I don't think anybody has said the wear pattern is off-center. It looks dead center to me.

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I compared mine to an original cart board and it looks fine.

 

Mitch

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10 hours ago, RevEng said:

I don't think anybody has said the wear pattern is off-center. It looks dead center to me.

 

i got two from Fred, one of them was off.  Al has that one now, maybe he can chime in.  I sold the other one, my WiFi-SD version is all I need, don't care about the 2 Activision games.  May just be a manufacturing problem.  It also behaved differently on various systems, I have.

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Kyljoy's Concerto is my old one. I sold it to him last year when money was tight.

 

I had several 7800's and it behaved differently on a few of them. Two A1 serial number models it worked almost all the time, with the exception that with Pokey plugged into it certain games crashed. (Ninja Golf, and one other.) Also on those two A1's, Midnight Mutants and Basketbrawl would crash about 5-10 seconds in, Pokey or not. All other 7800 games ran fine.

 

2600 games would work for the most part, but sometimes going from a 7800 game loaded to a 2600 game, the first time the 2600 game would crash, but on subsequent launches, it ran fine.

 

I also had an X serial number model, and every game ran flawlessly, but the menu system was garbled and unreadable. It was my "russian roulette/box 'o Chocolates concerto cart". Never knew which game you were going to get.

 

I also had an original 1984 model and everything on Concerto ran perfect on it, but that console couldn't detect paddles, regardless of Concerto, or CC2 (used to have one of those years ago too)

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Good news: I was able to repeat some of the integrity errors with Mitch's console by configuring my Concerto like the ones out there. I have a good idea about the cause now and will post up a new test BIOS once I have it error-free.

 

IMG_1482.jpg.54e94a10db485065930e668ef6f83628.jpg

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I am now able to repeat all of the loading errors. A day spent with my scope was able to pinpoint an excessively slow slew rate on one of the signals. A POKEY makes the slew rate even slower. In Harmony Encore mode, the slew rate is very fast, and this is probably why Concerto works perfectly as an Encore.

 

When viewing the waveforms, CH1 (top on the scope screen) is the waveform that the 7800 sees, while CH2 is basically what I wanted it to see. You can see the slew rate is very slow and apparently it is slow enough to corrupt loads.

 

So here is the before waveform and integrity results:

IMG_1490.jpg.cf4d792bcd36e393b2edafd7e339a74f.jpgIMG_1491.jpg.e28fe2cd35d141867a129051b5a3598c.jpg

 

Here are the results after changing a part:

 

IMG_1492.jpg.119db0edc58259d4722afc369cab3619.jpgIMG_1493.jpg.c59bf7f2803358bd0824fbf8b3099af0.jpg

The slew rate is much faster, the signal looks tons better and the 7800 agrees!

 

I haven't made any other changes to this Concerto. I am sending this one to Mitch to try out.

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Guess the time away really helped - you got this nailed down pretty quickly!  This is great news.

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Oh my gosh, that second trace looks so much better than the first! Congrats on tracking this down. Fingers crossed that this is *the* fix that will finally let you relax and make mad stacks of cash from all us eager 7800 lovers. :)

 

make it rain loop GIF by Chris Timmons

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2 hours ago, Jinks said:

Having a 100% Concerto will be great!! 

What part needs to be replaced? 

A resistor. What seems to be happening is that the various ICs (especially, the POKEY chip) add parasitic capacitance which slows the slew rate of the signal and makes it kind of dirty too. I calculated out a new resistor value that will maximally improve the signal quality but still work for the original intended purpose. I can change the resistor even more if I have to (if the value is still too large for all cases and situations), but this would also require changing out an IC as well, which I could do if I had to.

 

There is a possibility that a firmware fix could have worked in this case, but it would be difficult to manage as I would essentially be taking that hardware circuit offline and having firmware handle it instead, which isn't ideal and may make some future improvements very challenging, so instead, I think I just want to replace the resistor on existing Concertos.

 

The downside of this is that I will be issuing a voluntary recall of the 30 or so Concertos out there so I can replace this resistor. I wouldn't recommend an end user try this unless skilled with SMT soldering. This would be free for Concerto owners of course. Before I officially issue a recall, I want to first make sure Mitch has no issues on any of his consoles, and while I am at it, I will see if there is anything else I can improve on Concerto if I am recalling the ones out there.

 

One thing I have in mind is that between the 2015 and 2016 mini-releases of Concerto, I found a low-power version of one of the chips which should save about 40-60 ma of draw on your console. This could help those with various power-sucking mods. I might also see if there are any changes to the programmable logic I can do, as most end users probably can't update this themselves. In particular, looking at file dates on my computer, I see that the fusemap that enables POKEY @0450 might not be in the 2015 Concertos, so I would want to at least check that and make sure everyone has the latest.

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I better not try to solder mine. I would probably mess it up. Also the other mods your talking about I would not be able to do anyway.

 

 One user cut the pins of his to make it a 2600 multicart.. lol.. 

 

Edited by Jinks
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