No schematic and cannot determine why there is no horizontal drive signal.
This set has failed and the Horizontal output was bad. I have determined that there is no horizontal drive signal and have no way to find where it has failed. There is a high positive voltage on the base of the Hor. output transistor which is certain to destroy another transistor. I need a schematic and advice will be appreciated! J.
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May I know what is the real problem of your unit, I read this post and I believe this is a reply to you with one of our expert, but I can't see the thread of your original post. Also, please let me know the brand model no. of your unit, it will help to determine the fault.
Six blinks of standby light in Sony TVs denotes the absence of horizontal oscillation.
No Horizontal (H STOP), no raster, goes to the blinking self-diagnosis function immediately. Check C515 & 516 and the jungle IC, IC206. In most cases the Ic is foud defective. anyway check its soldering points for any loose contact, or bad solerings. Check the line drive transformer, a very little transformer soldered directly to the main printed circuit board, very close to the horizontal output transistor. Check its primary winidngs for open. If it gets open no horizontal drive signal will be present at the base of the horizontal output transitor, that also may the cause of horizontal stop.
first to check waveforms going into the vertical output stage. The supply voltage is probably correct since that often determines the size. It almost sounds like the waveform rather than being mostly on (active video) and off for the short blanking period is somehow only on during the last part of the active video thus giving you just the bottom of the picture. If there is a vertical output IC, it may be defective or the blanking input to it may be corrupted. The problem may be as far back as the sync separator. Then again who knows, maybe wait for the schematics.
CAUTION: To prevent damage to the CRT phosphors, immediately turn down the brightness so the line is just barely visible. If the user controls do not have enough range, you will have to locate and adjust the master brightness or screen/G2 pots.
Since you have high voltage, the horizontal deflection circuits are almost certainly working (unless there is a separate high voltage power supply - almost unheard of in modern TVs and very uncommon in all but the most expensive monitors).
Check for bad solder connections between the main board and the deflection yoke. Could also be a bad horizontal coil in the yoke, linearity coil, etc. There is not that much to go bad based on these symptoms assuming the high voltage and the horizontal deflection use the same flyback. It is almost certainly not an IC or transistor that is bad.
I assume this is the exact replacement transistor? If it is not then use the original part with no substitutes. Next be sure the transistor has heatsink compound applied and is securely tightened to the heatsink. You say the B+ is normal, but does it remain "normal"? I would monitor the B+ also at power up to be sure it is being regulated. Another critical issue is the drive signal at the base of the HOT. If you have a o-scope & schematic check this carefully not only for amplitude, but wave shape & timing. This determines the on/off time of the HOT. Check components in the base circuit (there are only a few) as perhaps they were damaged when the HOT originally failed. If you have a high voltage meter make sure the voltage is within spec. the retrace tuning cap. in the collector may have changed value allowing excessive amplitude of the pulse. One final thought, after running the set for a time is the HOT excessively warm. It should be slightly hot, but not to the point of burning your finger. If it is too hot I would be suspicious of the drive signal, and or heatsinking.
The most common fault with this model is the flyback transformer assembly is defective. Along with this, the horizontal output transistor may have also failed. In some cases this failure occurs because there is a drive problem coming from the horizontal scan driver circuit that is ahead of the horizontal output circuits. There may also be some support components that triggered the fault in the first place and would also be required to be replaced. When there is this type of failure, it is possible that the power supply may also need some service.
On more rare occasions, there may be a simple failure from the main power supply buss, or a failure in some other circuit that is putting the power supply in to protect mode.
An experienced TV tech who knows your model of Sony set can troubleshoot it and determine the exact failures. He can then give you an estimate.
This model of CRT set was considered to be an excellent TV set. Unfortunately when the full digital service is established as the standard, and the analog service is discontinued, you will require a digital to analog conversion box for this set to work with TV stations. Some cable TV and satellite TV companies will be supplying the analog signal in their standard package.
What you have lost is horizontal deflection, this is caused by loss of the horizontal drive signal to the yoke transformers on the CRTs, for all three of these to fail at the same time is not likely so what I think is that the drive amplifier may have malfunctioned. To check this you will need:
1) schematic diagram or service manual (to determine the proper voltages and signals on the deflection board) 2) Multimeter (to measure the DC voltages on the components of the deflection board 3) Oscilloscope (to view the waveforms on the deflection board)
With these three pieces of test equipment you should be able to troubleshoot this problem.
Now if you do not have this equipment and what to take a chance at a blind guess, and just replace a board, I would suggest replacing the deflection board, this board usually contains the flyback transformer, the Convergence modules (which can cause this problem also), and the connections to the yoke transformers.
Your main power supply may have failed or you've lost the horizontal drive pulse to the the horizontal output transistor. Also the flyback may be bad and the horizontal output transistor may be shorted. If this is the case the main power supply will not start up.
These are a few things that may have happened.
The horizontal output transitor is always connected to the primary winding of the flyback transformer (via collector) and also to the horizontal deflection coil via an electrolytic capacitor.
The most likely suspect for damaging the transistor is the fylback transformer. In some countries there are electronic stores that test flyback transformer by winding a few turns on the ferrite core and applying a test voltage. This test will only test the secondary.
The primary winding is difficult to test for turn to turn short because the resistance is quite low and you do not know the 'good' resistance.