Quote:
Originally Posted by Console User
Question to try to help a friend out. They have I believe a 1992 RCA Console with CTC 177AM2. They have real good color from the picture yet but when they use the set the Picture wants to pull from Left to Right. Any ideas what the issue could be? A Bad cap in the vertical circuit on the Main board or something else? Any ideas or help would be appreciated. I think it's a 27 Inch Set is what they told me.
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One of the unique things about the 177 was that it was totally software aligned, including the tuner. Other than the Focus and G2 pots on the flyback, everything else was done through the service menu.
What that means is that there is literally no symptom that could not be caused by a corrupted eeprom (where the alignment data is stored).
No sound? eeprom. Picture distorted? eeprom. Picture shrinking, stretched, pulling? eeprom.
The most common reason the eeprom gets corrupted is because of the bad ground structure in the tuner. RCA goofed a bit with this design in that the tuner ground shield and internal ground points are in series with the cold side ground of the power supply and the far side of the chassis. Any ground issues causes small spikes in the micro area where the eeprom lives and corrupts it.
The second reason the eeproms get corrupted is bad solder on the two large heatsink ground tabs where the low voltage regulator is and the where the horiz output transistor is. Solder both tabs thoroughly.
Any service of the 17X series begins with a tuner ground repair. If you don't intend to use the tuner, you can hard wire the cold side of the power supply bypass cap grounds to the microprocessor.
Once the grounds are done and the two heatsink ground tabs are soldered, service the chassis like any other.
Getting back to your symptom - you could be describing a bit corruption in the horiz phase or horiz osc adjustment.
After the tuner grounds are serviced (or bypassed), the procedure is to go into the service menu and adjust the horiz phase or oscillator adjustment(s) to see if the problem is there. Make note of all adjustment values before moving them. Careful with the horiz osc - if you adjust too high, it will go into shutdown and you'll have to add some capacitance in the horiz sweep to force the HV down so you can readjust.
If you can post a pic of the symptom that would help.
John