K7400 wigs out after a few seconds

[cadillacman]

for super low ohms:

Short your meter leads together....whatever it reads make that your new dead zero.

Ohm the resistor.

Subtract the shorted leads reading from the resistoer reading and thats your real reading.

 

[mecha]

I've run into a lot of 7400s and 7500s where I wound up reflowing a significant amount of parts. they didn't exactly do what yours is doing but if you tapped the side of the cab they would freak out. pulled it, 10 minutes later after hitting it with the iron they were solid again. I could beat the shit out of the cab then and they wouldn't jitter at all.

 

[ArcadEd]

Yeah, I have been over the bottom of the PCB again and again, nothing looks bad at all. Anything that is suspect, I wiggle and jiggle .

I haven't tried hitting it to see if it makes it worse, but it gets worse and worse the longer the monitor is on.

 

[Buffett]

is it the same problem as in this thread.

http://forums.arcade-museum.com/showthread.php?t=192800&highlight=7400+jitter

Peace
Buffett

 

[ArcadEd]

Possible, smalltownguy mentioned he was having the same problem in this thread.

The video you took and the one I took of mine doesn't seem similar.

My B+ isn't solid, it goes down as the problem starts and goes lower as the problem gets worse.

I'm going to read over the other thread and see what I learn .

 

[danpiraino1971]

Where did you order it from? Looks like it's an LA7851

I got one locally but Bob Roberts has them on his site for $4.00. i always get parts from Bob.

 

[ArcadEd]

Replaced U701 and it fixed the issue .