Angelzplay said: I just replaced the convergence IC's with STK392-180's. The picture is perfect now but the TV powers off after a few minutes and it won't come back on unless unplugged. Then it does the same again. Can someone help? My guess is that I need to replace a fuse or resistor but I have no idea how to find which ones.
If the TV worked normally before the visible convergence failure and replacing with STK392-180 ICs produces a normal picture for a short period of time, then shuts-down, don't use 180 substitute ICs. It is not the same as replacing a 60 watt light bulb with a 100W light bulb.
The TV shuts down because the 180 ICs produce higher "idle" current. The power supply safety protection circuit detects the excessive current and shuts down the TV. Unplug reset is required after safety circuit is triggered. Many times the 180 or 150 substitute ICs will cause the low ohm resistors to burn up. If you still have a "normal" picture while it runs, all resistors and fuses are ok.
Proof is to remove the 2 X 180 ICs from the circuit and run the TV. All will be fine except for a wildly distorted image with misconvergence. TV will run without shutting down and on-off will work normally.
Panasonic engineers are very clever, they have designed and built 10's of million TVs. Panasonic does not tell you to substitute 110 ICs with 150 or 180 ICs, only an Internet IC salesman who has never fixed Panasonic TVs will tell you this. If the salesman has fixed Panasonic TVs, he will know that this does not work.
Replace the STK392-110 ICs with 110 or 120 ICs only. (120 specs are very close to 110). Hitachi factory service will recommend a substitute for STK392-110 IC, but only if all low ohm resistors are changed to different values. The circuit must be re-designed to handle the extra current. Occasionally the 180 or 150 ICs will work and produce pre-mature failure of the low-ohm resistors or intermittant power supply safety circuit shut-down
The fad a few years ago was to install extra fans for cooling to compensate for poor quality or incomplete repairs and poor quality replacement ICs causing multiple failures. Now the fad is to substitute the wrong ICs for STK392-110s.
Wrong spec spark plugs may physically fit and appear to work in a car engine but valves can be damaged and performance will suffer. Wrong Convergence ICs may appear to work in your TV but problems (pre-mature failures) occur in many instances because the convergence circuit is designed for specs of the original part.
Our service department does many successful convergence repairs across Canada on different makes of TV on a daily basis. We always try to use the original parts that the circuit was designed for and do not heed the advice of the Internet salesmen regarding substitution of STK ICs. 560 ICs are no longer available so 570 are used in Sony, 110 ICs are not widely available and 120 will work because specs are very similar. Substituting 150 or 180 ICs for 110 ICs causes problems unless the circuit is re-designed and different value low ohm resistors are used (as specified by Hitachi).
Many ICs sold on the Internet are defective and will not work or have a very short life-span. The ones that have bright, clear, printing and flimsy leads should only be used for target practice.