I'm Working On a Hitachi 61" with a DB14G chassis. The origional symtom was no picture or sound and LED dp23 was out. I found the problem to be Q777 (2sc5681) and fp05 (2a pico fuse). I ran the TV for about 10 minutes or so after that and then Q777 poped again. I replaced it again and found some cold solder on the vertical IC. I also resoldered the the H drive transformer and a few other things around the circut for safe measure. It this point I've ran the TV for several minutes but that HOT is getting HOT so I've turning it off before that transistor hits it's saturation point. I Don't have a Schematic so I'm not sure where to go from here. B+ is at 160V seems right but not sure. I'm also not sure now hot It's supposed to run, I'm sure it runs pretty hot but what's too hot? maybe someone has ran into this and has some Idea's for me?
AT POWER ON, THE DEFLECTION CIRCUIT IS ENERGIZED: (See Figure 1 below)
When the Microprocessor outputs a High from pin 53 when power is turned ON, the high is inverted by Q003 to a LOW. This low is inverted by Q004 to a HIGH and routed through the PQS1 connector pin 2. This high is routed through R954, R951, D926 to the base of Q914. This transistor turns ON and it’s collector goes LOW.
This low is the Ground return for the Relay S901. The B+ for the primary of the relay is the SBY +5V generated by the switching transformer pin 15, rectified by D920, filtered by C935, L915, and C936.
When the relay S901 turns on, the contacts close and AC is routed to the Deflection circuit power supply and the Deflection Power Supply is Energized.
DEFLECTION HORIZONTAL DRIVE CIRCUIT ACTIVATION: (IC01 Rainforest IC)
When the set has AC applied, one of the switch pulses generated on the Sub Power PWB is the +11V pulse from pin 10 of the Switching Transformer I901. This +11V pulse is rectified by D919 and filtered by C929. This +11V DC voltage is then routed to the +9V regulator I906 pin 1. When the set is turned ON, the Horizontal Drive Power supply I906 is activated. This happens when pin 2 of I906 goes high with the Power On/Off control line from PQS1 pin 2. The +9V is output via pin 3 to the PQD2 connector pin 5. From here the +9V is routed through the Deflection PWB to the Signal PWB via PSD3 connector pin 11, through the coil LC03 to pin 19 of IC01 the Rainforest IC. When this voltage is applied to pin 19, the horizontal circuit inside the Rainforest IC is activated and a horizontal drive signal is output from pin 26. This H. Drive signal is routed through the PSD2 connector pin 5 to the base of the horizontal drive transistor Q709 on the Deflection PWB. The collector of Q709 produces a drive signal routed through the drive transformer T702 and output from pin 4 to the base of the Deflection Horizontal Output Transistor Q777 to begin driving the deflection circuit which in turn, activates the High Voltage circuit.
Two transistors monitor the SW +9V line, Q707 and Q708. When the set is turned off, the H. Drive signal from IC01 could stop too soon. If this were to happen, the Horizontal output transistor Q777 would be damaged. To prevent this, if the SW +9V line drops, Q707 senses this because it’s base voltage drops. The base of Q708 rises and turns on, grounding the output from the H. Drive Transistor Q709.
Thanks for the info Slinteriors, you've given me some idea's to investegate. As an update I did change the driver transistor but it's still running too hot. Driver voltages seem to be ok. Maybe I'll change the filter caps for b+ and driver circuts just in case there is some ripple I don't know about. Other than that I suppose I'll need to dust off the oscope and see what the wave form looks like coming out of the driver circut. I suppose it could also be a load problem. Unfortunatly I've still not isolated anything yet. I'll keep you posted.