Defender Cocktail - Auto Up/Manual Down Not registering

[sk8ersublime]

Hi everyone,

I recently was gifted a defender cocktail and during my initial troubleshooting found that I am unable to get to Test Mode. When I push the advance button I get to book keeping mode, but when pushing the auto up/manual down switch the behavior of the advance button does not change.

I bought the cocktail manual from tnt which has all the schematics.

So far I have done the following:
Checked the wiring is correct on the AU/MD switch. It is good.

Verified the switch isn't bad, tested with meter, switch is open and closed as expected.

Traced blue wire from switch to rom board pin 1 on 2J3 connector.

Verified the connector is making contact to pin 1.

Checked resistor value. Checked good.

Tested Pin 9 on IC24 (14049) on rom board with logic probe. nothing when switch is open, high when switch is closed. Pin 10 is always high.

Pin 2 on IC22 is also high. I don't see what this chip is though…and I'm not sure where the output would be. I highlighted the path of this in the schematic attached.

Any suggestion on what to check next? Or maybe I need to replace the 14049 on the rom board?

Thanks for any suggestions!

 

[mecha]

it could be the 4049, but in most circumstances I've seen it's the 6821 PIA that goes bad. out of curiosity do the 4 diagnostic LEDs on the rom board randomly flash or are the game sounds wrong or missing completely? these are all symptoms of bad PIA. the 4049s are also a common failure point though too, because they're CMOS parts and not TTL they're more susceptible of static shock wrecking them.

stuff to read: https://www.arcaderepair.net/williams-test-panel-information/

Williams ROM Board Information – mecha Arcade Repair

www.arcaderepair.net

I'll help you with this, PM me your phone number and we can talk whenever

 

[sk8ersublime]

it could be the 4049, but in most circumstances I've seen it's the 6821 PIA that goes bad. out of curiosity do the 4 diagnostic LEDs on the rom board randomly flash or are the game sounds wrong or missing completely? these are all symptoms of bad PIA. the 4049s are also a common failure point though too, because they're CMOS parts and not TTL they're more susceptible of static shock wrecking them.

stuff to read: https://www.arcaderepair.net/williams-test-panel-information/

Williams ROM Board Information – mecha Arcade Repair

www.arcaderepair.net

I'll help you with this, PM me your phone number and we can talk whenever

Thanks. I will do that, likely won't be able to work on it much today though.

As far as sounds, they seem to be correct to my knowledge, defender isn't a game I've played a lot honestly, it's too hard haha. I only noticed weird sound glitch once when I unhooked the rom board to look it over and test some of the traces and resistors. When I plugged it back in and turned on the game the first time, the start up sound was weird, but the next time I turned it on it was normal.

Thanks for posting a link to your site, I actually found that when working on it last night and it helped me verify the switches was wired correctly . I noticed the Defender ROM board info link says page not found FYI.

One thing I forgot to add, the harness has been a bit hacked up inside, and the memory interlock was cut out of the circuit. Not sure if this matters or not for this switch to function, based on the schematic the AU/MD switch seems to be fine using my ring test from the switch down to the board connector.

 

[sk8ersublime]

Update: this issue is now FIXED! Bad CD4049 on the ROM board. Shoutout to @mecha for chatting with me about this issue!

 

[mecha]

yeah, to reiterate, MOS chips are very voltage sensitive. those little glass caps coming off them won't be very good for static electricity or something else disastrous. (ask me how I know)

I started with computers before I got into fixing games and even way back when I always handle boards by the edges. it's additionally why I haven't been blown up taking G07s out with blown F901s and charged filter caps. to my credit also I've never used a ground strap before either.