ColecoVision components question

[G_P_T-0_1]

Hello! I've been scouring various locales online (especially the awesome AA forums) for information on correcting the graphical corruptions in my ColecoVision. As I've been reading previous graphical corruption posts here, it's become apparent to me that if the power switch and AC adapter are eliminated as sources of the corruption, that bad DRAM chips can be at fault.

 

I've got a couple of questions regarding this and other aspects of my newly inherited CV. I received this from some friends of the family a few weeks back. Upon connecting this unexpected gem to the TV, I was disappointed to see it had corruption in the graphics, so I decided to do some research and open the thing up to ensure that all is well.

 

First, it appears that someone who didn't quite know what they were doing had previously opened the console... capacitor 7 (C7) on the mainboard has a nice chunk taken out of the side where someone screwed into it when they reassembled the case, causing it to take on a crescent moon look. Obviously I don't think this is beneficial to the long-term health of my new CV so I want to replace it, but the rating is in a format I'm not familiar with.

• * Could anyone else on the forums let me know what their C7's rating is, or what the "104Z" rating printed on C7 means?
  * From a quick Google search, I think 104Z would == a ceramic disc capacitor at 0.10uF at +80, -20% tolerance. Can anyone confirm?
  

Second, it looks like I may very well need to replace some of my DRAM chips as the graphical corruption problem hasn't seemed to be remedied by implementing any of the other troubleshooting tips. Everything I've found online states that the DRAM chips in the CV are Mostek 4116 chips and that a confirmation of correct replacement chips is to read and ensure that the chips are simply marked as being "4116" - not any other series.

 

The DRAM chips in my CV are marked as being "MOSTEK ©8222 MK4315 J-3". I can't find this particular chip, or any information about it anywhere online.

• * I'm curious to see if anyone else has these 4315 chips in their ColecoVision, and if they have been able to successfully swap out one or two of these chips for the 4116 (or perhaps have to swap the whole bank at one time?)
  * Are the 4315 and the 4116 one and the same?
  * The other chips on the mainboard match what I've found online, e.g. the TI SN74LS541N so I have no reason to believe this is a knock-off of any sort.
  * The main board has "75743 REV F" printed along the top side of it, if this helps narrow down the possibilities.
  

I can definitely provide photos of anything you'd need to ID these components. Thanks!

[doubledown]

Here's the replacement capacitor (Ceramic Disc Capacitors 100V .1uF Z5V +80%/-20% Tol) you'd need:

 

http://www.mouser.com/Search/ProductDetail...uu2jKfxjw%3D%3D

 

Of the dozen or so loose ColecoVision PCBs I checked I saw 3 different VRAM chips, including the model you mention on a Rev. F board. But on another Rev. F board I have, it has the standard TMS4116-20NL chips. They're all compatible with each other and should be able to be inter-mixed. You'd probably have an easier time looking for the TMS4116-20NL though. There is a way to check them if you have a logic probe and the ability to use it. Another possiblity with visual garbage would be the VDP, the TMS9928ANL. Its the 40-pin chip right in front of the VRAM chips.

[G_P_T-0_1]

Thanks for the capacitor link - this looks like it fits the bill nicely.

 

Interesting information on the chips, however. What difference would it make to the operation of the ColecoVision to use TMS4116-15NL versus the TMS4116-20NL? (I ask because there's a lot of 15NL on eBay right now for a semi-reasonable price...)

 

I also think you may have the right idea as far as the TMS9928ANL goes, unfortunately. It looks like at some point someone tried to solder a new chip in, or perhaps just to resolder the existing chip as there's quite a bit of leftover burned looking flux(?!?!?!) on the underside of the board and a few really amateurish looking solder spots midway down the chip (including one pin that looks as if it has next to no solder on it at all - just floating in the pin hole).

 

I don't have a logic probe or the knowledge of how to use one at the moment, but I'm a quick study at these types of things and think I could learn readily enough. It's not as if I have to get the CV working in the next 12 minutes, after all... :-P

 

I think my path will be the following:

 

1. Reseat the TMS9928ANL in it's socket and hope I don't have to replace it.

* Do you know of a nice cheap source for replacement VDP chips, or what an average price for one should be?

 

2. If the reseating doesn't work, I'll buy a logic probe and troubleshoot the DRAM chips. I'll replace as necessary.

* Is there a chart perhaps that lists the internal ColecoVision boot screen's character map's memory addresses? The same letters are constantly corrupt on this screen, so I'm hoping maybe I can use this information to my troubleshooting advantage.

* Is it best to not rely on a map and go with the logic probe, if possible?

 

3. If the DRAM chips come out reading correctly, do you have any other suggestions on what I can check?

* The AC adapter is supplying the correct voltages; I've cleaned all contacts between the AC plug and the AC socket on the CV. I've tried a second AC adapter to confirm it's not an AC problem.

* The original awesome switch has been replaced with a much more reliable recent model.

 

Thanks again for your advice!

[classics]

The speed rating on those chips is not going to matter in the ColecoVision, you can use them as drop in replacements.

 

Steve

[intvnut]

2. If the reseating doesn't work, I'll buy a logic probe and troubleshoot the DRAM chips. I'll replace as necessary.

* Is there a chart perhaps that lists the internal ColecoVision boot screen's character map's memory addresses? The same letters are constantly corrupt on this screen, so I'm hoping maybe I can use this information to my troubleshooting advantage.

* Is it best to not rely on a map and go with the logic probe, if possible?

 

Hmm.... You mentioned some bad soldering on the chip. If the same letters are constantly corrupt, then this could be due to the poor soldering. (Or, if you're really unlucky, someone burned out a pin on the device. That seems less likely.)

 

According to my TMS9118/9128/9129 book (SPPS002, June 1984), the pinout for the TMS9928 is as follows. (The 91xx family was a software compatible family, and the book includes some 99xx documentation for comparison.)

 

 

Hopefully, armed with these details you might be able to focus in on the likely bad pins / bad chips. I assume that armed with knowledge of the boot-time config you can work out what the pattern table and name table addresses are, etc?

 

Oh, and one word of caution: This is the TI documentation, and bit 0 is the MOST significant bit rather than LEAST significant bit. So, in the 8 bit number 0x80, bit 0 is 1 and bits 1 through 7 are 0.

 

I've had this book for over 20 years. It's fun dusting them off to put them to good use. Maybe it might be worth scanning both VDP guides I have for the Coleco crowd someday?

 

(In case you're wondering, I did my first VDP programming in TMS9900 assembly language around 22 years ago with a TI Mini Memory Cartridge on a TI-99/4A. It was a great way to keep a 7th grader out of trouble, I guess.)

Edited August 14, 2008 by intvnut

[doubledown]

Steve's right about the speed ratings. The '20' on the standard ColecoVision VRAM chips refers to 20 nanoseconds, any number smaller than that would be faster and fine as a replacement. You might be able to go slower too, but your best bet is to stay the same or faster. As far as replacement VDPs, I've got about (20) right now. I usually hoarde them when I can find them on ebay for less than $50.00. By the by the cheapest one on ebay right now is at $50.00. If you need one let me know and I'll sell ya one for $25.00. As far as the power supply is concerned, don't always rule that out as a problem. Just because one power supply works on one console, but not another, doesn't mean much other than you should use that power supply for the console it works for. They're a finicky bunch, those CV power supplies.

[GonzoCV-1]

Steve's right about the speed ratings. The '20' on the standard ColecoVision VRAM chips refers to 20 nanoseconds, any number smaller than that would be faster and fine as a replacement. You might be able to go slower too, but your best bet is to stay the same or faster. As far as replacement VDPs, I've got about (20) right now. I usually hoarde them when I can find them on ebay for less than $50.00. By the by the cheapest one on ebay right now is at $50.00. If you need one let me know and I'll sell ya one for $25.00. As far as the power supply is concerned, don't always rule that out as a problem. Just because one power supply works on one console, but not another, doesn't mean much other than you should use that power supply for the console it works for. They're a finicky bunch, those CV power supplies.

 

 

Doubledown: You seem like "the man" on Colecovision things. I'm replacing the inductors on a Coleco board with some more moder versions with better (smaller) proviles. My board has a couple without color stripes. Do you know the values for the inductors that aren't marked?

[doubledown]

Off had I don't konw their values, they would need to be measured if they're not marked. Which componenets are they, L5 & L6?

Edited August 17, 2008 by doubledown

[GonzoCV-1]

Off had I don't konw their values, they would need to be measured if they're not marked. Which componenets are they, L5 & L6?

 

 

Naw, L5&6 (the ones by the switch) are low enough to the board as to not pose any problems. But the ceramic ones with the little horns are simply too much work. They're close enough to each other that they cannot be laid down on thier side, and modern ferrite core chokes of the same values are way too short.

 

The board I'm working on has three of these right below the place where the RF box is that have no stripes at all. They're the creamic objects with "horns"

--- if you've got access to a couple boards, let me know if yours are marked.

 

Thanks!

[doubledown]

The board I'm working on has three of these right below the place where the RF box is that have no stripes at all. They're the creamic objects with "horns"

 

Define "below" (looking at the PCB in its standard orientation, expansion module card edge to the front, joystick ports to the left) Are there component numbers on the PCB?

 

--- if you've got access to a couple boards,

 

[channelmaniac]

OK,

 

First off, the -20 refers to 200 nanoseconds and NOT 20. -15 refers to 150ns.

 

Anything the same speed or faster will work... -20, -15, -12, and -10 are all pretty easy to find.

 

If you want to experiment you might even be able to modify the unit to take different DRAM ICs. It's common to modify the Williams games that take 4116 DRAM to take 4516 (5v only 16k DRAM) or 4164 DRAM which would be more reliable and would NOT require the +12v and -5v supplies.

 

There are a lot of different part numbers for 4116 DRAM and they are compatible. Each manufacturer did their own thing. Just make sure to use good quality double-wipe sockets when replacing any chip so future repairs can be done easily.

 

I have a stack of Colecovision boards for parts and will be testing the chips. Any good VDP chips will be added to my website but it'll probably be another month before I get that done.

 

RJ

[GonzoCV-1]

If you want to experiment you might even be able to modify the unit to take different DRAM ICs. It's common to modify the Williams games that take 4116 DRAM to take 4516 (5v only 16k DRAM) or 4164 DRAM which would be more reliable and would NOT require the +12v and -5v supplies.

 

 

RJ

 

 

This is intriguing.

 

I think I'll try it in my Coleco portable project. I'm already replacing the VDP with the "18" version that outputs composite natively, so as to lose the need for the RF box and daughter board. But lowering heat dissipation would be a big deal. I'll have to trace the board to see where else the -5 and +12 voltage are used, I know the -5 still comes in at the controllers, but this is interesting.

 

Thanks.

[Ikrananka]

GonzoCV-1 - have you seen this thread?

 

Perhaps you could comment there on the work you're doing and your Coleco portable project - it may have some bearing on the "fan made system".

[+5-11under]

Gonzo,

 

I would definitely go with the 4164 as an "almost direct" replacement for the 4116... especially for a portable... I think the only other parts that use +12V or -5V are video parts, which you may also be able to get around.

 

Hmm... the original page seems to have disappeared... http://web.archive.org/web/20060517061134/...m/Dramming.html

 

If you're making a new PCB for the portable, it'd be worth some effort to see if there's a single RAM chip that would be able to replace the 8.

 

Thanks,

5-11under

[GonzoCV-1]

Gonzo,

 

I would definitely go with the 4164 as an "almost direct" replacement for the 4116... especially for a portable... I think the only other parts that use +12V or -5V are video parts, which you may also be able to get around.

 

Hmm... the original page seems to have disappeared... http://web.archive.org/web/20060517061134/...m/Dramming.html

 

If you're making a new PCB for the portable, it'd be worth some effort to see if there's a single RAM chip that would be able to replace the 8.

 

Thanks,

5-11under

 

 

Guys, I'm not doing anything quite that exotic. More of a "Ben Heck" style deal. You know, "cut the original mobo down as small as possible and jam it in a portable case with some batteries and a 5" LCD."

 

Actually, I've got an ambitious idea for hacking the entire coleco circuit board in half, as I've identified a spot where this would in theory work pretty well, so as to make even a smaller portable, but we'll see. I'll tackle that one when I'm done with this one.

 

As for the voltages, I know for sure that the CV drives the controllers with a negative voltage signal swing as I saw it on the occiliscope when I ran the thing. I'd guess that with all those diodes, when it swings the controller to the second state that permits it to read the binary encoded matrix for the right button and keypad, its needing the negative voltage to deal with diode voltage drop. I hate working with neg. voltage, though so who knows. If I could find a way to get rid of the -5, I would!

 

As for +12 I'll have to trace the board a bit. I know +12 it drives the switch IC that toggles A/V from the Coleco parts to the signals coming from the expansion port on their way to the RF daughter board, but since I'll be taking A/V from my replacement TMS9918 chip and the sound chip directly, I wouldn't need that stuff. We'll see. I want to get all the capacitors updated and deal with this memory idea first.

 

I'd love the idea of a "modern" Coleco. But you'd have to get the IP from whoever owns it now. (River West? Or did they by only the IP that wasn't previously conveyed to CBS and, if memory serves, Telegames wound up with?)

[doubledown]

The board I'm working on has three of these right below the place where the RF box is that have no stripes at all. They're the creamic objects with "horns"

--- if you've got access to a couple boards, let me know if yours are marked.

 

Thanks!

 

From left to right:

L15: Orange, Red, Black

L2: Brown, Black, Black

L3: Brown, Black, Black

 

Surprisingly I checked another board first and that one had 4 in that same location. The 4th one was to the left of L15 and labeled L8. Hope it helps.

[GonzoCV-1]

The board I'm working on has three of these right below the place where the RF box is that have no stripes at all. They're the creamic objects with "horns"

--- if you've got access to a couple boards, let me know if yours are marked.

 

Thanks!

 

From left to right:

L15: Orange, Red, Black

L2: Brown, Black, Black

L3: Brown, Black, Black

 

Surprisingly I checked another board first and that one had 4 in that same location. The 4th one was to the left of L15 and labeled L8. Hope it helps.

 

Interesting. My board has a jumper at L8.

try

I'm delighted that those two are values I've already purchased for elsewhere on the board! I wish I had a "variety" to work with, but most of the Coleco's that have passed through my home have been simple Composite video upgrades for friends.

 

Much thanks. I'm off to search out 8 of these drop in replacement memory chips and to trace around this sucker to try and see if maybe I can get rid of the +12 step up regulator when I run this sucker of batteries, as that's $20 part!

[G_P_T-0_1]

...

I've had this book for over 20 years. It's fun dusting them off to put them to good use. Maybe it might be worth scanning both VDP guides I have for the Coleco crowd someday?

 

(In case you're wondering, I did my first VDP programming in TMS9900 assembly language around 22 years ago with a TI Mini Memory Cartridge on a TI-99/4A. It was a great way to keep a 7th grader out of trouble, I guess.)

...

This is awesome, thank you for this. I only hope there's something I can offer you in the future to help you out. If you would be inclined someday, I'd sure be glad to get my hands on scans of your VDP documentation. I'm sure at least a few others would be pleased to have them as well.

 

By the by, it turns out most likely (I'm 98% sure) that I have some bad DRAM chips, so I ordered a few of them (plus spares) which I expect in any day. I'd like to seat these in some IC sockets, but I want to ensure there's no drawbacks which anyone may know of in doing so. Sockets shouldn't make ANY change in timing, latency, static issues, etc... as long as everything is properly seated and soldered, right?

 

Also, would it be worth it to attach a heat sink to all of the replacement chips? I've read here and there that heat can be one of the possible factors in these chips going bad from time to time... Do sinks really decrease the heat enough to avoid failure for any meaningful amount of time? Is DRAM failure usually caused by heat, or do other factors contribute? If so, what are these factors?

 

Thanks for your time and answers!

[G_P_T-0_1]

Steve's right about the speed ratings. The '20' on the standard ColecoVision VRAM chips refers to 20 nanoseconds, any number smaller than that would be faster and fine as a replacement. You might be able to go slower too, but your best bet is to stay the same or faster. As far as replacement VDPs, I've got about (20) right now. I usually hoarde them when I can find them on ebay for less than $50.00. By the by the cheapest one on ebay right now is at $50.00. If you need one let me know and I'll sell ya one for $25.00. As far as the power supply is concerned, don't always rule that out as a problem. Just because one power supply works on one console, but not another, doesn't mean much other than you should use that power supply for the console it works for. They're a finicky bunch, those CV power supplies.

doubledown, I may actually be interested in obtaining one of your VDPs even if mine does seem to be in working order right now. I'm sure one of my harebrained schemes down the road will necessitate having a spare on hand.

 

*mourns the loss of a Stella chip who valiantly died in the quest to see if I could indeed watch Blake's 7 while soldering one night...*

 

I'll let you know when I'm in a position to buy one from you!

[GonzoCV-1]

Hey guys,

 

I'm halfway blind from tracing my Coleco Board, but I thought I'd let everyone know that the memory chip swap suggested above looks like a very good mod. For my portable / handheld Colecovision project, it should let me do away with +12 alltogether, as the only other place on the whole board +12 is used is in driving the video switching (using the HEF4066 under the RF box), and of course, on the daughter board to mix the Y and color diff signals. In fact, it looks like the designers put the video signals on a 12v carrier for the simple purpose of interfacing with the LM1889N chip in the daughter board -- interesting choices they had to make in using off the shelf components to make the Colecovision.

 

Since I'll be eschewing the whole color dff thing by replacing my video processor with the "18" suffix variant (a drop in pin for pin replacement that provides composite out instead of color differencing), I will have no need for the daughter board, and since its a portable with no expansion module possibilities, I can probably depopulate that whole area of the board to save power.

 

Alas, I was right that the -5 signal is tied to the controller inputs. So I'll still have to wire in a voltage inverter, but the ability to skip the 12v is a very welcome development.

[channelmaniac]

Alas, I was right that the -5 signal is tied to the controller inputs. So I'll still have to wire in a voltage inverter, but the ability to skip the 12v is a very welcome development.

 

You should be able to find a cheapo +5 to -5v inverter in a 24 pin package that will make easy work of it.

 

RJ

[intvnut]

...

I've had this book for over 20 years. It's fun dusting them off to put them to good use. Maybe it might be worth scanning both VDP guides I have for the Coleco crowd someday?

 

(In case you're wondering, I did my first VDP programming in TMS9900 assembly language around 22 years ago with a TI Mini Memory Cartridge on a TI-99/4A. It was a great way to keep a 7th grader out of trouble, I guess.)

...

This is awesome, thank you for this. I only hope there's something I can offer you in the future to help you out. If you would be inclined someday, I'd sure be glad to get my hands on scans of your VDP documentation. I'm sure at least a few others would be pleased to have them as well.

I'd post them straight away if my scanner were faster. :-) I have two interesting books: The TMS9118 / TMS9128 / TMS9129 Data Manual, and the Video Display Processors Programmer's Guide. Each is a bit over 100 pages, which would take a few hours to scan each with my scanner. Doable, but slow. I wouldn't mind getting these out on the 'net though eventually.

 

BTW, you did read that right. The data book is for the TMS9118 etc., not TMS9918. The two are related. The TMS9118 has a modified DRAM interface (so it's not a drop in replacement), but it can, as a result, use 2 4416 DRAMs instead of 1 4116 DRAM. The data book also goes into detail about the memory timings, so if someone does do a custom board, this might be an interesting set of chips to find for compactness sake.

 

By the by, it turns out most likely (I'm 98% sure) that I have some bad DRAM chips, so I ordered a few of them (plus spares) which I expect in any day. I'd like to seat these in some IC sockets, but I want to ensure there's no drawbacks which anyone may know of in doing so. Sockets shouldn't make ANY change in timing, latency, static issues, etc... as long as everything is properly seated and soldered, right?

I don't think they will make a noticeable difference. IIRC, the DRAMs were socketed in my TI-99/4A. I know the VDP itself was. I do know from one of the members of the VDP design team that the VDP did really push the DRAM timing specs, so if you do have a flaky DRAM, I imagine the VDP will notice it sooner than anything else. (I was hired into Texas Instruments by a guy who was on the TMS9918A VDP design team. He's the guy that added the bitmap mode to the TMS9918A. It cost 50 transistors, in case you're curious. :-) ) He also mentioned that since it was pushing the process technology of the time (the 10.73MHz was pushing it a tad), it was sensitive to its power supply level. I imagine this explains the recurring "Clean your power switch!" suggestions for CV owners.

 

Also, would it be worth it to attach a heat sink to all of the replacement chips? I've read here and there that heat can be one of the possible factors in these chips going bad from time to time... Do sinks really decrease the heat enough to avoid failure for any meaningful amount of time? Is DRAM failure usually caused by heat, or do other factors contribute? If so, what are these factors?

 

Thanks for your time and answers!

Honestly, I have no idea. 4116s are a mystery to me. I remember when I was first starting to learn digital logic 20 years ago, and I saw the +12v and -5v going to those chips and a mention in a hobby magazine that "DRAMs are hard to interface to," and I kinda swore them off then and there. (For a jr. high kid with no budget, I think it was the right move at the time.)

Edited August 19, 2008 by intvnut

[HARMIK]

Hey guys,

 

I'm halfway blind from tracing my Coleco Board, but I thought I'd let everyone know that the memory chip swap suggested above looks like a very good mod. For my portable / handheld Colecovision project, it should let me do away with +12 alltogether, as the only other place on the whole board +12 is used is in driving the video switching (using the HEF4066 under the RF box), and of course, on the daughter board to mix the Y and color diff signals. In fact, it looks like the designers put the video signals on a 12v carrier for the simple purpose of interfacing with the LM1889N chip in the daughter board -- interesting choices they had to make in using off the shelf components to make the Colecovision.

 

Since I'll be eschewing the whole color dff thing by replacing my video processor with the "18" suffix variant (a drop in pin for pin replacement that provides composite out instead of color differencing), I will have no need for the daughter board, and since its a portable with no expansion module possibilities, I can probably depopulate that whole area of the board to save power.

 

Alas, I was right that the -5 signal is tied to the controller inputs. So I'll still have to wire in a voltage inverter, but the ability to skip the 12v is a very welcome development.

 

 

When you say daughter board do you mean this

[intvnut]

...

I've had this book for over 20 years. It's fun dusting them off to put them to good use. Maybe it might be worth scanning both VDP guides I have for the Coleco crowd someday?

 

(In case you're wondering, I did my first VDP programming in TMS9900 assembly language around 22 years ago with a TI Mini Memory Cartridge on a TI-99/4A. It was a great way to keep a 7th grader out of trouble, I guess.)

...

This is awesome, thank you for this. I only hope there's something I can offer you in the future to help you out. If you would be inclined someday, I'd sure be glad to get my hands on scans of your VDP documentation. I'm sure at least a few others would be pleased to have them as well.

Well, I went ahead and scanned most of one book and put the scans here. The book I scanned was the Video Display Processors Programmer's Guide (SPPU004). I scanned up through Appendix D, and I scanned all the text pages at 300DPI as line art. At Appendix E, they start giving listings for demo programs for various instruction sets, and so I stopped scanning there.

 

In this whole scanning process, I thought scans 43 and 44 were interesting, because they describe a variant of Graphics II mode that wasn't in the original 9918A docs. Scan number 47 references the AVDP (Advanced Video Display Processor), which was never released by TI. Instead, TI licensed the architecture, leading to the VDPs in the Sega Master System and beyond.

Edited August 19, 2008 by intvnut

[channelmaniac]

The 4116 DRAMs are sensitive to power issues moreso than heat.

 

Granted, if they are running hot enough that it's uncomfortable to hold your finger on them, then yes, heatsinks will help. That's rarely the case on these DRAMs though.

 

On the arcade games if you have cracked solder joints on the +12v and -5v supply connectors you'll start randomly popping DRAMs. Williams games are bad about that. One of the fixes is to resolder the connector or replacing it if it's arced and burned from the current trying to cross the cracks.

 

Of course, the biggest fix is to mod the board for 4516 or 4164 DRAMs.