Another Arachnid 6000 problem

[Doughbroz]

Works fine for a few minutes, both in play and idle mode, then locks up. Might just be low +5, which is always 4.92. If so, how do I raise it? +12 is always 11.5 volts. When it locks up in idle screens, the target lights go bright. Disconnecting the coin door and target head, and removing the pushbutton bulbs makes no difference, nor does chilling board components, none of which seem to be warm anyway. It works for the same length of time whether being played or idle. It can be locked up all day, but will play normally for a few minutes if I turn it off and right back on. I have swapped chips where possible, the large cap screws are tight as Dick's hatband, and all connections and solder joints are good. Any ideas? Thanks

 

[cadillacman]

id replace the 5 volt regulator. id then reflow the solder(actually scrape back the solder mask to add more solder) at the rectifier.

I woudl then do what i always do whish it to add a fan blowing across that power supply to keep it cool.

I would also check for ac ripple in the dc voltage... those power suplied get krappy capacitors over time.

 

[Doughbroz]

OK, thanks. I'll start with that.

 

[cadillacman]

and if i remember right the 5v regulator can be had at most "good" radioshacks, its a common one..

and i just used a 12v fan tied into the power supply...

 

[KenLayton]

The most common failures of that power supply are (listed in importance):

1. Bad bridge rectifier

2. Bad solder joints/connectors.

3. Bad +5 volt regulator

4. Bad green mylar (a.k.a. "chicklet") capacitors. There are two of them located between the two large heatsinks. These prevent the +5 volt regulator from breaking into oscillations as it heats up. Quite frequently the heat from both of those transistors has internally damaged the two capacitors and they need to be replaced with the same types.

 

[Doughbroz]

Thanks Ken.