Rastamafugg
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Posts posted by Rastamafugg
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I know this is a long-dormant topic, but did anyone ever try to replace the 6809 in the Vectrex with a 6309? I'm going to be opening mine up to apply the buzz kit when it arrives, so I was thinking of doing the swap at the same time, but I was hoping someone has tried it out before and posted their results.
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Maybe I'm having a bad googling day, but I can't find a list of serial numbers for the Coleco Adam (Or Colecovision, for that matter, although I found an old forum link to a defunct Colecovision serial database). Is there one out there somewhere that I'm just not finding, or even an explanation of the number sequence? Mine is A8102735. I expect A represents the factory and 81 might be the year of manufacture, meaning mine is the 2735 unit made in late 81, possibly? That seems early, chronologically, though.
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I located some assembly books for the coco. I think what I'm looking for is registering an interrupt handler for IRQ, which fires 60 times a second. If I'm reading that correctly, though, does that mean the IRQ interrupt fires at the same point in the display cycle? And is that predictable? (eg: start of the vertical blank?)
I'll try asking some of the sources Michael linked to above, as well.
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Is there a good source for code examples using the various interrupts available for the Coco? Preferably Basic09/Nitros9 examples, but I'm having trouble finding anything online other than what is documented in the service manual documentation. I'm particularly interested in inserting code to run when the HSYNC and VSYNC interrupts trigger, but I can't seem to find any examples or tutorials for Coco interrupt handling in general.
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29 minutes ago, Tursi said:
Nah, we're THAT far. Barry Boone released a set of libraries and source code back in 2000:
I found this line in the readme interesting:
QuoteThe MBX is communicated with via the joystick port. Basically, you issue commands to the MBX in the form of a send queue, and wait for responses from the receive queue. An interrupt routine (the 60Hz interrupt) is used to manage communications to/from the unit.
I'm curious to see how that queue was implemented. If the communication was via the joystick port, I wonder what the cassette port was used for?
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18 minutes ago, arcadeshopper said:
I have like..4. is there a shortage of these?
To answer your question, if I'm correct, the unit was only on sale for a few months before it was discontinued (Sept-Nov 83?). Anything cancelled that quickly must have sold really poorly (although video game crash of 83 certainly helped). Most units that are out there were probably bought on discount after it was discontinued, so I would guess the number of units out in the wild would be in the low thousands (maybe even high hundreds). Nothing but a not-so-educated guess on my part though. ?
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9 minutes ago, arcadeshopper said:
I have like..4. is there a shortage of these?
If you ever wanted to part with one, I'd love to add one to my collection! It would be interesting to put an oscilloscope or a logic probe on a working system!
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28 minutes ago, pixelpedant said:
In principle, is it possible? Sure, probably. Ultimately, with FPGAs, anything like this is possible, even when original chips are scarce.
It's just a matter of the MBX being a product in which at best dozens of people have any serious interest, and even they (I certainly not least among them) aren't all that interested. Which mainly comes down to the very small library available for the machine, and the essentially non-existent resources/tool/documentation for developing new software for it.
If the MBX is ever going to get any traction, the first step isn't building a full-fledged clone system. It's dumping and documenting the ROM and how serial communication with the TI-99 works and understanding the fundamentals of the machine's and its software's functioning. Even just to the point where it's possible to create simple demos. And we aren't even there yet.
That alone is a big project that I'm not sure anyone's take up as their cross to bear. It sure would be nice! But I can't really expect someone to take that up, in principle.
Who knows though. Maybe someone just shows up on day and says "Championship Baseball was the defining experience of my childhood and 6809 assembly is my jam, and I'm going to figure this machine out!"
One can dream.
Still, as I say, the dream there is just seeing the machine *thoroughly documented*. That doesn't actually build you a clone system.
Good points, thanks! Your YouTube videos on the MBX were the primary inspiration for the question. I didn't realize the machine hasn't been fully documented yet. That would have to be done first, for sure, and would require original hardware to help reverse engineer the system. I wonder how good MB's internal documentation for the system was? Although it sounds, then, that not even schematics survived the decades.
I grew up with an MC-10 and Coco 2 at home, so I'm more familiar with the 6809 in that context. I used a few Ti99's growing up briefly, but I'm pretty much starting from scratch learning the system itself. I'm curious about that serial communication between the two systems. It uses both the joystick port and cassette port to communicate, which seems like a weird choice when the side port was there. Someone with some serious hardware hacking skills must have come up with that solution! Does that mean it only sends input data back to the Ti99? Any sounds/speech it generates come out of its speaker (although, if it's connected to the cassette port, I wonder why they didn't try to push an analog audio source through there?), and I assume the voice recognition would work by converting the voice command onboard and sending the relevant joystick/touchpad command to the Ti99.
On a side note, is/are the original designer(s) of the MBX known? If they were still around, that would make a fascinating interview!
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Has anyone tried to make a reproduction of the MBX as a whole? I've seen some joysticks built from new parts, but I was wondering if the the main box is reproducible in 2022? I couldn't find any attempts documented online through my searching.
I know the heart of it is a 6809 processor, and it relies on the Ti99 for video and some of the game sounds (other than what it drives out its own speaker). Are there any custom chips that can't be sourced today? I don't see why the touchpad, joysticks, and mic interfaces couldn't all be replicated.
I love obscure hardware add-ons for old computers, and this is one of the weirdest I've seen. Shame it's so rare.
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Yeah, that's what happens when you are retro-browsing in two different playgrounds! Meant to post this in the Tandy group!
I also just picked up a FinalGrom99 and was doing some Ti99 deep diving and mis-posted!-
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I recently picked up a Model III that needs some TLC (a mouse made a bed under the floppies and the power cable was cut). I want to also replace the RIFA caps on the two power supplies in the machine. When I read tutorials online, like this one, they indicate there should be 3 caps to replace. This is a picture of the floppy power supply in my machine (the two are identical). I only see the larger RIFA cap, and the layout of the board is quite different from the ones I found online. Maybe a later revision? Do I just need to replace the one RIFA cap on each board?
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3 hours ago, -^CrossBow^- said:
The only issue with this, is that he is using that with his Dragon fly cartridge I believe and the creator of the DF cart was very clear about not providing more than 9v to it.
But @Rastamafugg also stated it does this with his original 7800 PSU and that seems to be providing enough input voltage at over 12v so that again points to something internally in the 7800 bringing things down.
Rasta: using the original 7800 PSU plugged in, what is the voltage reading off the leftmost leg (As you are facing the rear of the mainboard) when it is powered on with a 2600 game in it because that should be at 9v. Then power it off quickly and plug in a 7800 game and power it on and get another reading.
Now it's not powering on at all. ? I'm wondering if there is a cold solder joint or something only loosely connected. Going to have to go over the board with a magnifying glass, I think.
I have a bench power supply arriving on Friday. Providing I solve this issue, where do I connect on the board to provide +5V to the system main logic and bypass the power circuit (as you mentioned in a previous post)? -
1 hour ago, -^CrossBow^- said:
also it came in handy for stunning mice we would find inside the registers when servicing local grocers so we could remove them.
?
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6 hours ago, Stephen Moss said:
Interesting hypothesis. I agree that the input voltage seems a little low, but not excessively, I wonder what the spec of the power unit is if not an original Atari 7800 PSU.
As far as I can see everything runs off 5V, I don't know how much extra current is consumed in 7800 mode compared to 2600 but even if the PSU is a little under rated current wise although the ability to regulate the voltage would be diminished even with 5V in I would expect 5V out of the regulator.
That sounds like either a thermal fuse in the PSU has tripped or the voltage regulator has gone into thermal shutdown which would be worrying considering the size of the heatsink, but it could just be a bad solder joint loosing connection with thermal expansion.
If it is a thermal shutdown that could indicate that something may be shorted/drawing too much current, the additional current draw could also explain the previously reported lower than expected input voltage as it drags the PSU down. Although the voltages in post #58 seem more normal.
If you can get hold of some freezer spay, if anything other than the regulator is drawing an excessive amount of current it would defrost much quicker than anything else.
That would be a good test if they can do it, plus the current reading on the PSU might indicate if something is creating an excessive current draw.
I am not sure what the dragon fly passthrough is but if it can be easily removed it may also be worth doing so to eliminate that as a possible cause.
The last set of voltages I posted were with the original Atari PSU. The PSU I've been using with the Dragonfly is a Berls adjustable PSU set to 9v DC. When the 7800 stops powering on, it doesn't matter which power supply I use, the light doesn't come on.
What is freezer spray? Is there a particular product I should be looking for?
As for a bench power supply, can anyone recommend a good one for retro computer testing? -
On 10/22/2021 at 8:47 PM, -^CrossBow^- said:
Okay, so now you brought up the DF cart. Have you been trying to use it the entire time for 7800 games?
The 8.5 might be accurate but I thought it was a straight passthrough so should still have the same volts on the output cable as it does going into it.
So you show 10.2v powered on using an original 7800 PSU? What is the reading with it powered off at the ferrite bead? It should be basically the same as all of that is before the flip-flop actually powers on the system.
And with the original PSU what the input voltage on that right most leg of the 7805 as your are facing the rear of the mainboard? That really should be about 9v.
So I read with the original PSU:
At the bead powered off: 12.4-12.7vAt the bead powered on: 10.4v
At the right most leg of the 7805: 10v
It won't stay powered on long, though, with the original PSU. It powered off while testing and won't turn on again.
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1 hour ago, -^CrossBow^- said:
Okay, so now you brought up the DF cart. Have you been trying to use it the entire time for 7800 games?
The 8.5 might be accurate but I thought it was a straight passthrough so should still have the same volts on the output cable as it does going into it.
So you show 10.2v powered on using an original 7800 PSU? What is the reading with it powered off at the ferrite bead? It should be basically the same as all of that is before the flip-flop actually powers on the system.
And with the original PSU what the input voltage on that right most leg of the 7805 as your are facing the rear of the mainboard? That really should be about 9v.
Ok, didn't understand you wanted me to test with the adapter connected but 7800 powered off. Here are the readings from that bead:
12.75v original psu off8.94v dragonfly pass-through off
She doesn't want to start again, so any powered tests will have to wait until morning.
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6 hours ago, -^CrossBow^- said:
This all points to power to me as being the main issue here.
So here is what you do:
When it is powering on, measure the input voltage like I stated before. Black probe on ground somewhere on the board and Red on the ferrite bead. What is the value?
When it isn't power on, measure again to see what it reads?
Measured the end of the ferrite bead closest to the big cap...
Powered off: 2.37vPowered on (9v dc via a brand new power supply through my Dragonfly cart using the pass-through power connector): ~8.5v
Powered on with the original 7800 power supply: ~10.2v
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Here's another symptom... At some point during testing, the 7800 stops powering on. If I leave it for some time (hours at least), it start powering on again. Don't understand why that is happening.
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1 minute ago, -^CrossBow^- said:
Well it would only cause an issue if it were in a permanent PAUSE ON type position.
Do you have an older 2600 game like Pitfall or combat you can put in and see if it comes up in Black and White?
Also there is usually tape just under the cartridge sleeve as I believe it was originally there to hold the cart slot and space in place during the initial soldering. But I've never seen red before as it is always masking tape white or beige.
I have Combat, and I'm pretty sure it was in color, but I can test it again.
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2 minutes ago, -^CrossBow^- said:
Yes because with the back of the board facing you, that means that the pins off the VR would be 3,2,1. Pin 1 is the input voltage, Pin 2 is Ground, and Pin 3 is the output voltage.
Your output voltage is fine, but the input is too low. Likely enough to provide current for the 2600 side to work but not enough for the 7800 side. Now you need to measure the voltage from ground to the ferrite bead just before the large filter cap. That will be your input voltage.
Is this the bead you are talking about?
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2 minutes ago, -^CrossBow^- said:
Looks to have been made around early May of 1987. So strange to me to still see the expansion port installed but also see the extra timing circuit fully in place. The resistor off that Sony RAM is completely normal. I think pretty much every 7800 I've seen with Sony RAM has that resistor off the WE pin on one of the chips. And while that 4013 is a 4013, I've not seen that brand used. I can't tell what brand it is exactly? It looks like it might have the Ti logo on it but it is much smaller than I'm used to seeing on their ICs.
Still what we know at this point is that it isn't a power issue most likely because he is able to boot up and play 2600 games without issue. It is only the 7800 side of things that is failing here. What is that red fabric or tape on the right side bottom of the cartridge sleeve? (Left side in the pic)
WAIT! Where is your Pause button?!@
Missing apparently. Could that be causing the problem?
The red plastic is stuck to the board, I believe. I'll take the plastic cartridge slot off and take a picture.
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I also picked up a logic probe. Are there any tests I could do with that that might help troubleshoot the issue? First time using one, for me.
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On 10/18/2021 at 10:34 AM, -^CrossBow^- said:
Correct and it looks like the NTE185 is an equivalent part to the original MJE210 that was originally there. So we know that was replaced as well it would seem.
@Rastamafugg the 7805 that was being talked about is hard to miss. It is screwed down to the large black metal plate centered behind the cartridge port. To take the measurements we are asking about:
Have the back of the mainboard facing you so that the power port is on the left etc.
Have the black probe anywhere on ground on the mainboard.
Use the Red probe to measure the input voltage on the right side leg of the regulator when the console is powered one. Should be at least 9v and could be more higher depending on the initial input voltage.
Then use the Red probe to measure the left leg on the regulator and that should be right at +5v. As @Stephen Moss stated the center pin is ground and will have a 0v reading.
If you want to measure a little safer, you can attach the black probe to any ground point on the board and then use the Red probe on the left large center trace on the top of the board that runs down the middle roughly. That is the main +5 rail.
I tested with the back of the board facing me and tested the 7805. I got ~4.96v in the left pin and ~7.66v on the right pin. Are you sure those values are supposed to be reversed?
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On 10/13/2021 at 5:18 PM, Mitch said:
Sorry. Yes, I am referring to the one connected to one of the RAM chips. If there is one.
Mitch
Here's a picture of the complete board. There is a resistor connected to one of the Sony chip's legs
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Coleco Adam Serial Number List
in ColecoVision / Adam
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@rietveld Thanks! Looks like my guess at the serial number meaning was wrong about the year. I'll have to take a look at the dates on the chips when I open it up for some maintenance to figure out when mine was made.
That's an impressive Coco collection! You've got a lot of interesting peripherals hiding in the corners of those pics, too. And a good collection of Ataris and other systems off to the side! That first picture is pretty much my first two computers growing up. Radio Shack was right next to the arcade in the mall, so I spent a lot of time there when my mom or dad went shopping.