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View Full Version : bad color crystal? ctc17 08-07-2009, 11:59 PM What would the symptom of an off frequency colorburst crystal be? One of my Zenith sets takes 45 minutes for the color to kick in and when it does the tint is all the way to one side to get the correct color. I had an issue with an rca like this once and if i rember right it was the crystal. What would happen if the crtstal drifted just a little? MelodyMaster 08-08-2009, 12:15 AM What would the symptom of an off frequency colorburst crystal be? One of my Zenith sets takes 45 minutes for the color to kick in and when it does the tint is all the way to one side to get the correct color. I had an issue with an rca like this once and if i rember right it was the crystal. What would happen if the crtstal drifted just a little? The crystal is trimmed with a capacitor or occasionally a coil. Also the phase comparator may have a bad diode (not an issue with a ringing-type crystal driver) or the burst may be weak due to misaligment or parts failure. Since in fact the set does produce locked colour I'd guess the crystal is good. drh4683 08-08-2009, 07:34 AM Does it only show color rainbows, or simply no color b/w picture only? What chassis are you working on? andy 08-08-2009, 09:26 AM --- ctc17 08-08-2009, 10:41 AM Does it only show color rainbows, or simply no color b/w picture only? What chassis are you working on? I do get the rainbow if I turn the color all the way up. I cant find the chassis number on this one. Its the chassis that has 1 transistor in the video circuit and the afc can. The rest is tube. (If that helps) The schematic that seems to be very close is 20x1c36 Don Lindsly 08-08-2009, 11:34 AM Replace the color osc, AFC and burst amp. Then run through the color AFC alignment per the instructions. Zenith26kc20 09-22-2009, 04:15 PM Check the negative voltage on the control grid of the 3.58 oscillator also. It should be at or higher in voltage (more negative) than indicated by the schematic if the crystal is good. Use a low cap probe to do this. Preferably the DC probe setting on a older VTVM. ctc17 09-22-2009, 10:44 PM Im pretty sure its the crystal is just off frequency. I had an rca that did the same thing and it was the crystal. I just need take the time to pull the chassis out and change it. Been working on another Zenith. |