Commando PCB Help

higgilo

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I'm new to the hobby, and have some questions. I am restoreing a dedicated Capcom Commando Machine, and I am stuck. I have stripped out the cabinet, recapped the monitor and it works and looks great.

However when I power up the PCB I get nothing but random characters in the game colors. The Game has worked while in my possession, So I know it has worked. I have gotten sound letely, but since pulling and resetting all the eproms I have gone back to random characters on the screen. I Was careful with the eproms and all the pins are seated correctly.

If needed I can post pics of the screen.

Thanks for any help.
 
Check the power at the board. Make sure that all voltages are correct. If this is a switching power supply the adjustment can (and will) drift over time. You need to check it periodically.

IIRC, Commando has two boards.If it does, check the interboard connector. That can sometimes cause issues.

ken
 
Thanks, I have +5.58, +12.22, and -6.67v. is this far enugh out of tolerance to cause problems?
Is it worth while replacing components in the power supply, like caps. I is a open body chasis, so all is easily accesable.

This commando actually has 3 boards, and I suspect the cable may be the problem as the symptoms come and go as I remove/reseat the ribon cables. Should I just check these for contunity, or should I ohm them to check for high resistance?

Thanks for your help

Ryan
 
Those values are dangerously high. They should be +5.0V +12.0V and -5.0V. Look for some type of voltage adjust potentiometer or knob or something. Post some pictures of you can. There are a lot of knowledgeble people on this board who may recognize the power supply and can tell you how to reset the voltages.

I pulled my Command board out of the storage box and the cables would be my first guess as to a connection issue.

The problem with those ribbon cables is the terminators. The wires work temselves loose over time. You need to carefully crimp the terminators. I use a wide jawed set of pliers so that I can put pressure on the top and bttom at the same time. First I put a piece of cloth, I normally use a shop towel or a scrap of t-shirt, over both top and bottom of the terminator. Then very gently squeeze the top and bottom to compress the ribbon cable back onto the metal teeth in the base of the connector.

If you want to try this, first try to locate the one that is giving you the most problems. You can usually do this by just gently pressingon the cable either at the terminator or pressing on the ribbon cable itself right next to the terminator. Then shut everything down pull the cable and try gently recompressing it.

ken
 
Here is the power supply pics. I have the schematic, and there are no pots or adjustments. Add one?
 

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Never run into one like that. Which is not too suprising, there are hundreds of variations out there. If nobody else knows where the adjustment is on that beast, you might want to look into replacing it. They are about $20 + shipping new. Or you could ask in the parts wanted forum. People are always getting rid of these used.

One of the more standard designs is this one: http://www.twistedquarter.com/index.php?main_page=product_info&cPath=1&products_id=4 (there are other places to get them, I just use twistedquarter because it is easy to remember the web address :)).

It has a voltage adjust knob on the front.

ken
 
thanks for the help, I ordered a new ps, and am going to wire in some pots in the meantime.

I'll let you know what happens
 
Installed new Power supply, same problem.
All I get is the first photo.
I accidently left off one of the ribbon cables and got the third photo with sound.
I checked the ribbon cables and recrimped as instructed.
Is it time to learn how to use a logic probe? and if so what is the least expensive good one and where do I get it.
Thanks
 

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A lot of times when graphics are messed up, carefully removing and reseating the ROMS will fix the graphics issues.

Worst case, I have a Commando or two removed from some games I restored back to their original games. Let me see if I grabbed a wiring harness and can get one running. It may be a couple days before I get a chance to look for it.

ken
 
Does it try to play with bad graphics or is it dead?

If it's dead, you probably have a bad ROM or RAM chip(s) thanks to the overvoltage problems from the old power supply.

RJ
 
Thanks everybody. I've got another pcb comming soon. I'll keep you updated.
If I did zap the roms can they be reburned or are the chips bad? I am going to start checking the ic s to see if they got burned.
 
Got another commando pcb off ebay for a steal, looks like it was run over by a truck. However it works great. Now starts the board work on the one in failure.

Thanks for the help, it was quite a learning expirence.

Ryan
 
Good luck. The commando I pulled out of the closet needs some serious help. It won't run at less tha 5.65V at the power supply and then it runs the attract mode, but when it is coined up, to halts and the graphics get messed up. First approximation is that I have a bad cap in there somewhere dragging the voltages down. Sorry I can't be of any more help, but if you have a working board now, if you run them in parallel, it should help the logic probing.

ken
 
Run them in Parallel? Help

Connect them up to seperate power supplies so that both are running at the same time and then you can measure test points on the good one and then the bad one. It helps to find where the logic has gone south when you have a known good board to test and then immediatly go test the bad board.

ken
 
I am having the exact same problem with my Commando. Fortunate, I have a working spare. I have narrowed the problem to being on the small outer pcb. I am guessing I am going to need a little more than my multi meter to check these roms, as I don't have a logic probe. My programmer should be in by the end of the week though.
 
I am having the exact same problem with my Commando. Fortunate, I have a working spare. I have narrowed the problem to being on the small outer pcb. I am guessing I am going to need a little more than my multi meter to check these roms, as I don't have a logic probe. My programmer should be in by the end of the week though.

you can use a multi meter to check them. a logic probe is faster and easier to read. You just set the multi meter to a low dc voltage and watch the changes. Some meters are not fast enough for this though. I have done this in the past before I built my logic probe and then I bought one.
google 'logic probe plans' and you probably see the one I built. It is almost the same price to buy one on ebay as it is to build ~20
 
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