ColecoVision freezes on boot

[Jess Ragan]

What the title says. I only have Super Game Module games at the moment and can't test anything else. It's worth noting that I replaced the controller chips on the system before this happened. Could this be the cause?

[Jess Ragan]

The system doesn't work with either SGM games or standard games... it immediately freezes on boot. And now I'm frustrated and have no idea how to fix what ails this blasted machine. All I know is that the problems started after I installed the two controller chips, so I must assume that's where the problem lies. What would make this system freeze on boot that's related to the controller chips? Anybody...?

[Stephen Moss]

I don't really know much about this system and just had a quick look at the controller input schematic, if by the two controller chips you mean the 74LS541 then check that there were inserted the correct way round and if soldering was involved check for shorts between pins.

 

As you say, the fact the issue started after you replaced them suggest there is a connection between the two events (particularly if it was immediately after), if one of the output enable lines is active when it should not be that could result in contention on the data bus lines as some parts of the system are trying to drive data lines high while the signals via the controller chips are trying to pull it low, that would result in junk data that would potentially cause a crash.

 

You might also want to check the status of any reset pins the system has to make sure that things like the processor are not being held in reset and that it is getting both a clock signal and correct power. I don't think I would be able to suggest anything else not being very familiar with the system.  

[Jess Ragan]

Hey, I appreciate the input nevertheless! It gives me some idea of what I should do next.

 

The controller chips are bound together by wires on the board. Unfortunately, a couple of those wires got burned by the soldering iron and no longer seem to make a connection. What I did was make more connections on the underside of the board. Now the system functions for about a second before freezing. I think I need to check my work and make sure the burned wires aren't making connections elsewhere. (Maybe I'll sever the faulty wires on the top of the board, I dunno.)

[CPUWIZ]

PRO TIP: Post pictures along with your explanations of something like "burned wires", etc.! 

[Jess Ragan]

I'll keep that in mind. It would probably be easier for me to show you what the problem is if I hadn't already soldered in the socket, though.

 

Basically the two chips are joined by a series of diagonal wires on the top of the PCB. A couple of these wires were overheated and lifted off the board. I figured if I folded them back down and carefully set the socket into their loops I could re-use them, but that clearly did not work. What I think I'll need to do now is remove the socket entirely, cut the offending wires, and make the connections on the underside of the board instead. Anybody have ideas on how to remove the socket with minimal irritation? I've got desoldering braid, a soldering iron, and a solder sucker. That's it. Hopefully it won't be such a bear to remove the socket, because getting the original chip off the board was a total pain in the butt. (Luckily, I've got about nine more sockets, so if the old one gets trashed while I'm desoldering it, it won't be a problem to replace it.)

 

Stephen, you were right, by the way. Luke from Console5 just contacted me and said that yes, the controller chips are an essential part of the system logic, and if anything is wrong with them, it could lead to a halt of program execution. So at least I know what the problem is and how to solve it.

[ChildOfCv]

Most likely, with traces lifted, there are data lines that are shorted.  It may be best to remove to lifted traces entirely, inspect carefully for others that might be stealth-lifted and are now making contact with their neighbors, etc.  Then run replacement wires on the bottom side.

[Stephen Moss]

On 8/2/2024 at 7:07 PM, Jess Ragan said:

I figured if I folded them back down and carefully set the socket into their loops I could re-use them, but that clearly did not work.

Well it could have worked as it is something I have done before but it also depends on whether or not the hoels were plated through (I suspect not givent the ages of the system) as then it would be best to solder the pin on both sides of the PCB as the solder would not necessarily track down through the hole to make a connection on the other side if just soldering from one side. Thus soldering from both sides ensure the top and bottom side traces to the same pin are connected, and if the lifted track are on the top then using turn pin sockest are better as you have something although there is not a lot of space ot get a soldering iron in ther ewithout melting it at least it gives you something on the top side to solder the top side trace to.

 

The copper sheet is glued onto the PCB befoer it is etched, os too much heat applied during desoldering mealts the glue causing them to lift, I presume you did not glue them back down first as it does not occure to many people to try, it may not may not have helped, but generally if you can find a point on the same side of the PCB to solder to and are not a proficient solderer you are probably better off removing them and replacing with wires.

 

On 8/2/2024 at 7:07 PM, Jess Ragan said:

Hopefully it won't be such a bear to remove the socket, because getting the original chip off the board was a total pain in the butt. (Luckily, I've got about nine more sockets, so if the old one gets trashed while I'm desoldering it, it won't be a problem to replace it.)

That depends on whether or not the PCB has plated through holes as they are much harder to desolder with braid/a solder sucker as there is often solder left in the hole that you cannot remove and focable pulling the pin out can remove the through hole plating resulting in an open circuit between the top and bottom layer tracks (could be fixed by soldering the pin on both sides of the PCB but not something people always consider), a vaccume pump desloder station is better for plated through PCB's but can be too expensive a purchase for occasion use.

 

If your intention is to discard the IC after removal rathe then test/socket it then if you and have not tried it before in future you could use side cutters to cut off the IC legs at the case then grip them with pliers to pull them out having melted the solder, then as a separate operation go back to the joint and use the briad/solder sucker to clear the hole. That may help resuces the amount of time you spend continously heating the joint and thus prevent it from lifting.  

[Jess Ragan]

After joining two of the broken connections on the underside of the board, I was able to get the ColecoVision to run for two whole seconds before it crashed. I was told by the Console5 guy that the CPU might be to blame, and to test that with a multimeter to make sure it's working properly. So I guess that's what I'll be doing. I'm going to hold off on repairs until my new soldering iron arrives, though, because my old one suuuuucks and is long overdue for retirement.

 

(Wait, if the CPU is busted, where would I get a Z80A chip to replace it? I heard Zilog doesn't make them anymore. Are there third party clones?)

 

I can remove the chips from the sockets easily enough, but I can't remove the sockets from the board, at least not yet. I think the socket pins don't stick out far enough for me to be able to clip them, so I'm probably going to have to desolder, then resolder the whole thing. Gee, what fun. Can I heat up a metal wire, tuck it up next to the metal pins, and put the soldering iron on it to make desoldering a little less time-consuming? Seems like that would work, provided that it doesn't get so hot that it doesn't scorch the board.

 

 

[Jess Ragan]

Okay... it's a little late, but I've got pictures. It's pretty messed up on the top... hopefully not to the point where it's unsalvageable. I'm going to have to make some connections on the underside of the PCB to make up for the broken ones. Also, the wire running through C10 was damaged, so I'll have to put in a patch wire to fix it.

 

I know, I know, it's not great work. My iron was obviously too hot, but it's since been replaced. (Perhaps not soon enough, heh.) Removing the socket was not as tricky as I thought... I just divided it in half, cut what pins I could with a flush cutter, then bent the pieces back and forth to break them off.

[Jess Ragan]

I think I'm getting this. The two controller chips are linked pin for pin, which is why the second chip is set in reverse. Problem is, some of those traces are burned out, including pin 1, and the pin 1s of the two controller chips are the farthest apart. So that'll be a, heh heh, "fun" challenge.

[Jess Ragan]

I've got it! I've friggin' GOT it! Turns out that some of the wires that connect the two controller interfaces together had been cooked by my last soldering iron. (Why do soldering irons seem to melt everything but the solder?) So I connected a bunch of thin wires to the underside of the system and clamp clamp kabam, we've got a picture. Frogger runs as it should, without freezes. However! There's no sound (something on my composite mod must have come loose) and I haven't tested the controller ports yet. That's going to be, heh, kind of important!

 

More news as it happens. Thanks to everyone who offered suggestions! Things are looking up!

 

(Also, don't believe the hype about stranded wire, at least not for delicate work like this. Even after being tightly wound and tinned, it unravels when you start to solder. Single core solder was a lot less troublesome for me.)

[Jess Ragan]

Weird. The sound started working out of nowhere but the controllers themselves are unresponsive. Everything seems to register as "up" but actual up! Weird. Thinking I'm gonna need a little more time with this. Possibly some wires got shorted on those electrostatic discharge shield thingies on the underside of the board.

[Stephen Moss]

3 hours ago, Jess Ragan said:

(Also, don't believe the hype about stranded wire, at least not for delicate work like this. Even after being tightly wound and tinned, it unravels when you start to solder. Single core solder was a lot less troublesome for me.)

Generally it is OK, but unravelling happens to us all at some point, it depends on what you are trying to solder and how good a solder you are, i.e., trying to put it through a hole that is not wide enough will cause It happen every time.

As a general rule of thumb using single strand/solid core wire (typically 1/0.6) should be uses from connection on the PCB and multi-strand (7/0.2 should suffice) for connection from the PCB to an off PCB item such as another PCB or panel mounted connector/switch.  

[Jess Ragan]

I think I burned one of the long 8 pin "thick film resistors" with my soldering iron. Would damage to this component keep the controllers from working properly? Where can I get replacements?

[Stephen Moss]

 

Looking at a schematic I presume you are referring to either U25 or U26, they are called SIL (Single In Line) resistor networks and come in different variations as some have multiple individual resistors with a connection to each end of the resistor, some have internal parallel/series resistance network connections, but the most common type and the one that you will probably need is the commoned version where one end of all the resistors are internally connected to a single common pin (usually connection to the positive supply or GND).

 

From the schematic they appear to be used as pull-up resistors for the controller inputs, therefore if the common was damage that would likely affect all controller inputs, if it was just one of the resistor then only the controller signals affected by that one resistor will be affected. But you may have just done cosmetic damages to the outer casing without actually damaginh the component itself.

If I have not miscounted the schematic shows 7 pull-up resistors on the controller ports, so you will need a 7 resistor pack (8 pins, 7 for resistors + 1 for common) but the schematic I am looking at does no indicate a resistance value, either the value and/or a manufactures part number will usually be printed on the outside so it should be possible to work it out if you do not have access to a schematic or parts list that shows the resistance value.

 

Most big electronic component retailers such as RS, Farnell/Newark, Mouser should stock them.

Edited September 11 by Stephen Moss

[+-^CrossBow^-]

On 9/10/2024 at 12:01 PM, Jess Ragan said:

I think I burned one of the long 8 pin "thick film resistors" with my soldering iron. Would damage to this component keep the controllers from working properly? Where can I get replacements?

Look here as @rednakes1 just dealt with this same issue back in July and found a proper replacement:

 

 

[Jess Ragan]

Thanks guys, I guess that'll be the next thing I try to fix. (I feel for Rednakes... I was having the very same problems with lifted traces.) Not having much luck finding that particular part online... are there suitable replacements?

[+-^CrossBow^-]

56 minutes ago, Jess Ragan said:

Thanks guys, I guess that'll be the next thing I try to fix. (I feel for Rednakes... I was having the very same problems with lifted traces.) Not having much luck finding that particular part online... are there suitable replacements?

That thread I linked to has the PN he ordered in it?

 

4608X-101-223LF

 

Both Digikey and Mouser sell this.

[rednakes1]

1 hour ago, Jess Ragan said:

Thanks guys, I guess that'll be the next thing I try to fix. (I feel for Rednakes... I was having the very same problems with lifted traces.) Not having much luck finding that particular part online... are there suitable replacements?

Hi Jess,

 

If you can’t find that part number in stock, then you just need to look for these specs on Digikey or eBay -

 

22kOhm 7-resistor array (each is 223 ohms), 8 pins

[Jess Ragan]

FWIW, I appreciated the information offered directly.

[+-^CrossBow^-]

10 hours ago, Jess Ragan said:

FWIW, I appreciated the information offered directly.

I thought I set it to share the link to the actual post where he had the PN listed? Maybe I didn't? In any event, that PN I did provide shows in stock in Mouser. I didn't check Digi because Mouser is closer to me for shipping purposes so I tend to use them whenever I can.

 

https://www.mouser.com/c/?q=4608X-101-223LF