Bloodstorm PCB controls sticking

I picked up a bloodstorm pcb and am having some issues with the controls.

On player 1 down, button 1, 2, and start are registering as held down.

On player 2, down is the only thing being held down.



It's running on my homemade supergun, but I get the same thing even with no controllers connected. My other pcbs work fine with no issues. I've looked over my wiring and the pcb to make sure that those inputs aren't bridged with ground anywhere and cleaned any dirt off.

I can't seem to figure it out. If i could just fix the player 2 down button it would be playable.

Any help would be appreciated. Thanks!

Do any of the resistors near the jamma edge looked borked? Start at pin 18 and look to the right along the resistors.

I don't see anything out of the ordinary.

Check the 1K x 9 resistor networks and the HCT541's

I checked out the resistors. On the one located at r80, it gives me 206 on pin 2. They are all labeled 10x-1-472. I get 468 or 467 on the other pins. (if I'm measuring them right)



I've found the 541s. How would I go about checking these?

I'm going by this manual.
http://www.arcade-museum.com/manuals-videogames/B/BloodStorm.man.pdf

Thanks for the help so far!

I am assuming your measuring from pin 1 to the rest of the pins. Pull up resistors are typically always 4.7K. If you are seeing 206 ohms on any pin than the resistor pack is faulty or in worse case scenario the input to the control interface chip if there is no galvanic isolation (opto coupling) which I don't see. To be sure test the resistor pack outside the circuit.

EDIT

Looking over the schematic it looks like the inputs go to some 74hc541 U21 and U24 buffers which would provide protection between the harness and the input interface because the 541 would take the bullet.


If you want to check the 541 IC you will need either a DSO or more affordable and easier to understand logic probe, hell even a multimeter will do in desperation. Do you have a understanding of simple digital logic. Logic will be either high(4-5V) or low(0V). The buffer chips are simply bus line drivers, what logic level goes in is the same that comes out. For example P1 down button is connected to pin 8 on (74hc541) U21 as you can see from the schematic. Under normal circumstances when you are not pushing down on controller P1 pin 8 input is being held high by a pull up resistor therefore the output on pin 12 MUST also be high. When you push down on P1 you are pulling that same input pin to ground so the output also then goes low to ground.

Try testing a input that you know for sure is working to get clarity.

Thanks a bunch. I checked the resistors out of circuit and they are all good. I'm pretty sure I've got several bad 74hc541s. I transplanted the 541 for player 3 controls onto player 1 and now I can play on player 2 no problem, but I get continuous coin inputs and only up and left on the joystick for player 1. All player 1 buttons work. No more stuck inputs though.

I can't find any 541s for replacement online, only 541a. Would those be a suitable replacement?

What do you mean, it's a common component, this is a drop in .

http://www.mouser.com/ProductDetail...=sGAEpiMZZMuiiWkaIwCK2VGJzXkUQsJSGVbqfRM1Z48=

Cool, I'm not real knowledgeable about these things. What difference does the letter on the end make anyway?

BLEAGH said:

Cool, I'm not real knowledgeable about these things. What difference does the letter on the end make anyway?

Click to expand...

It differs by device and manufacturer. Most often it designate the package type, that might or might not be the case here but the fact is the part I linked is a drop in.