Model # 25TR19C221, Turn set on and High voltage comes up to about 28K and the set shuts down. Flyback rings ok using the scope cal jack. Have 130VDC to the H-out transistor, I did find the Vert IC shorted pin 6 (vert supply) to pin 5 (output). Replaced the IC, But still wont stay on. Tried reducing the line voltage, still will not stay on long enough to check anything. Cant get any fault codes, Anyone have any tips on this one? Thanks Charlie snipped-for-privacy@bellsouth.net
Measuring HV is not particularly useful except to tell you that the horizontal and high voltage circuits work.
DO NOT reduce line voltage. This is a switch mode power supply which will try to draw more current to compensate. You will learn nothing by reducing line voltage, and may cause further damage.
These sets have circuits that sample vertical and horizontal sweep so that they can shut down to protect the CRT in case of scan loss. Since the vertical section was blown up, I would start there. Verify that you have both supplies to the vertical IC, at least during the second or so that the flyback runs before shutting down. If so, are you getting a ramp on the output? If not, figure out why. If so, check signal path through pulse buffer transistor to processor.
These are not the easiest to work on, due to complexity and SMD parts, many of which are on the side of the board you can't get to. So be prepared to be patient. I chased one around for a couple days before finding an open zerohm SMD that isn't shown on the schematic.
This type of fault can get complex, and require a lot of patients. If the vertical scan is still failed, the set will not be allowed to start. It is also possible that the flyback is defective, or there is something on the secondary side that is loading it.
If the CRT is defective, the set may also go in to the protect mode. You can usually check this by removing the CRT socket assembly, and then seeing if the HV will come on and stay on. If so, then you know that there is a short in the CRT.
If you get high voltage, after shutting the set, make sure you discharge the CRT at both the anode cap, and at the socket end before putting back the socket assembly.
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JANA
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"Charlie East" wrote in message
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Model # 25TR19C221,
Turn set on and High voltage comes up to about 28K and the set shuts down.
Flyback rings ok using the scope cal jack. Have 130VDC to the H-out
transistor, I did find the Vert IC shorted pin 6 (vert supply) to pin 5
(output). Replaced the IC, But still wont stay on. Tried reducing the line
voltage, still will not stay on long enough to check anything. Cant get any
fault codes,
Anyone have any tips on this one?
Thanks
Charlie
ceast@bellsouth.net
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