Re: Troubleshooting a Proton VT331 SMPS
This morning I connected the lightbulb to the side of the resistor that is not lifted and it worked. The resistor is cutting voltage down to 2vdc. Is that part of the circuit only suppose to have 2 vdc going through it under normal operation? I am not sure.
olec280
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Last Activity: 05-08-2015, 08:37 PM
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Re: Troubleshooting a Proton VT331 SMPS
Under load (lightbulb) the voltage drops from 137vdc to roughly 2vdc.Leave a comment:
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Re: Troubleshooting a Proton VT331 SMPS
PlainBill,
Did you attach the image with the circled transistor?
Is is the transistor with the zener tied to the base or the one above it?
Thanks for you help.Leave a comment:
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Re: Troubleshooting a Proton VT331 SMPS
I lifted one end of R445 which is tied to the base of the H.O.Transistor through transformer T401. The voltage on the lifted side of the resistor reads 137vdc, also terminal 2 of the flyback on the print reads 137vdc. It is suppose to read 117. Also there was no ticking sound.Leave a comment:
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Re: Troubleshooting a Proton VT331 SMPS
Would it be reasonable to think that I can follow the next component in the circuit off the 115vdc and create a circuit gap following that component then check for the voltage. Now that I think about it, I may not be able to it cause of traces. I know the voltage is incorrect at the H.O.T, but I guess what I am hearing is it may be down stream of that point as well. Similar to how I suspected the smps originally. I tried to blow up a section with the H.O.T....Leave a comment:
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Re: Troubleshooting a Proton VT331 SMPS
I noticed the same thing with the diagram. I can probably blow up an area before converting to jpg, but the diagram is dense. The smps was the only diagram that was large enough to easily, read, copy, and use.Leave a comment:
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Re: Troubleshooting a Proton VT331 SMPS...Leave a comment:
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Re: Troubleshooting a Proton VT331 SMPS
Removed wire from S12 connector going to H.O.T from pin 1 for B+ voltage. Attached S12 connector, turned tv on. Had 117 vdc on pin 1 (bulb bright), 35.4vdc on pin 4 and 15.0vdc on pin 5. This tells me I need to look on the next schematic page, cause I think the smps is working fine.Leave a comment:
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Re: Troubleshooting a Proton VT331 SMPS
Here is the complete schematic for the smps....Leave a comment:
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Re: Troubleshooting a Proton VT331 SMPS
Connected the lightbulb and it shined brightly from the 117vdc output, s12 pin1.Leave a comment:
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Re: Troubleshooting a Proton VT331 SMPS
I'll scan it with a 11x17 scanner tomorrow.
Voltages at S12 are Pin1 62vdc, Pin 4 41 vdc, and Pin 5 9.8vdc.
I'll try the lamp test tonight.
New images. Hopefully easier to read until I get the full page scan.
There is overlap with the images....Leave a comment:
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Re: Troubleshooting a Proton VT331 SMPS
More Information:
The TV makes a very rapid tick, tick sound for lack of a better descripton after it is on for several seconds. No picture of course. Did have sound. Using isolation transformer. SMPS is installed during troubleshooting. Paying attention to hot and cold grounds.Leave a comment:
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Re: Troubleshooting a Proton VT331 SMPS...Leave a comment:
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Re: Troubleshooting a Proton VT331 SMPS
I did change all the caps on the output side of the rectifiers that are responsible for the two bad voltages. I figured that woud be an easy place to start. They did not have any effect.Leave a comment:
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Troubleshooting a Proton VT331 SMPS
I am troubleshooting two voltage problems on the SMPS. The B+ voltage is at 62 VDC at the collector of the H.O.T. What I have read leads me to the SMPS. I have 105vac at the input to the rectifier after the transformer. The output is 62vdc should be 117vdc. Also, the 18V output from the smps is at 9.8 vdc but the voltage into that rectifier is 15.6vac. I have replaced all the caps after the rectifier and even the rectifier itself. No help. I am wondering what causes a low B+ voltage? The TV is about 20 years old. I have the service manual. This is a tinkering task for me. Assistance is app...
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