K7400s kiling H.O.T.s

QbertWPC

New member
Joined
Feb 20, 2010
Messages
225
Reaction score
0
Location
Corpus Christi, Texas
Got 2 K7400s in for service.

One has had a cap kit and bad HOT replaced, put it in a game and a month later, it came back to the shop with no picture. Found it to be a bad HOT again. Have replaced it again, and this time the monitor didn't come on, and 10 seconds later the SMPS was ticking(Shorted HOT again.) I found the degaussing coil wires had been touching a heat sink and had melted insulation, creating a possible short, fixed wires, and the monitor is still blowing HOTs, even with the degaussing coil unplugged.

The second chassis I pulled from a game on location with a shorted HOT. Replaced the HOT in the field and it blew again instantly.

What do I check now?
 
The flyback, probably, although anything direct-shorted in the horizontal section can cause this...
 
Also, check the polypropylene caps in the horizontal deflection circuit for shorts.

Edward
 
did your HOT use a insulator between the heat sink and the transistor? Did you check the diode that sits near by?
 
Back
Top Bottom