Hi Guys,
First post. I have been trying to fix this Grundig Xentia 82 CRT TV for some time with mixed success. The schematics for this TV and it's various boards is available here:
Problem:
The blue information from the TV signal and video inputs is missing intermittently. Red and Green are rock solid.
Points to note:
Boards in the TV:
Action taken to resolve, and results:
1) Opened and removed boards, vacuumed, reassembled.
Result: Blue returns but disappears after a few hours.
2) Checked as many Electrolytic capacitors with a ESR meter from the boards and main board as I could reach, and the values seemed to be in range. I couldn't get to them all. Reassembled.
Result: Blue returns but disappears after a few hours.
3) Searched the schematics for blue lines, but most appear to be along surface mount components. There was a blue line on the Processing Board, but the Electrolytic capacitors on the board didn't appear related. I re-soldered the capacitor joints in case of dry joins. There was a Film capacitor on the Processing Board that was on a blue line, and I replaced that as I had one handy.
Result: The blue became solid again for around 2 weeks. Then occasionally it would drop out. A few days later, is was half and half, and now the blue only shows for a few seconds every hour.
What help do I need?:
1) I would like to know if the behaviour of the TV with the intermittent blue, does it seem like the work of a faulting Electrolytic capacitor? Or would it seem more like the behaviour of dry joints?
2) Could someone please explain what the Processing Board, Feature Box and the Signal Module boards do? I spent most of my time trying to work on the Processing Board, and it seemed to bring back the blue for the longest period. Was this a co-incidence? Am I working in the right area for the blue signal from TV and inputs?
If anyone could provide any guidance I would be very grateful, as I love this TV and it is way too good to replace just yet.
First post. I have been trying to fix this Grundig Xentia 82 CRT TV for some time with mixed success. The schematics for this TV and it's various boards is available here:
Problem:
The blue information from the TV signal and video inputs is missing intermittently. Red and Green are rock solid.
Points to note:
- The blue from the setup menu is still present which rules out a problem with the blue gun. Possibly also rules out a problem with the CRT Panel.
Boards in the TV:
- Main / Chassis Board (like a motherboard)
- Socket Board (contain SVHS socket)
- Processing Board contains VGA Socket and several chips:
C161RI 16-Bit Microcontroller
M27C160 "EPG-PLATTE" EPROM
UM61256 15 Watt DC-DC Converter,
MC74HC4094 8bit Shift Register/Latch
M24C16 serial I2C bus EEPROM
"TEXT" 68-PIN PLCC chip
TDA8601 IC RGB Fast Blanking 16DIL
Other misc chips, ram, latches. - Feature Box Board, which contains chips like:
SDA9362 DDC-PLUS-deflection controller
SDA9400 Scan Rate Converter
SDA9280 Display Processor - Signal Module, contains:
Tuner,
VIF/TUNER AGC - CRT Panel
- AF Module
- Other small misc boards
Action taken to resolve, and results:
1) Opened and removed boards, vacuumed, reassembled.
Result: Blue returns but disappears after a few hours.
2) Checked as many Electrolytic capacitors with a ESR meter from the boards and main board as I could reach, and the values seemed to be in range. I couldn't get to them all. Reassembled.
Result: Blue returns but disappears after a few hours.
3) Searched the schematics for blue lines, but most appear to be along surface mount components. There was a blue line on the Processing Board, but the Electrolytic capacitors on the board didn't appear related. I re-soldered the capacitor joints in case of dry joins. There was a Film capacitor on the Processing Board that was on a blue line, and I replaced that as I had one handy.
Result: The blue became solid again for around 2 weeks. Then occasionally it would drop out. A few days later, is was half and half, and now the blue only shows for a few seconds every hour.
What help do I need?:
1) I would like to know if the behaviour of the TV with the intermittent blue, does it seem like the work of a faulting Electrolytic capacitor? Or would it seem more like the behaviour of dry joints?
2) Could someone please explain what the Processing Board, Feature Box and the Signal Module boards do? I spent most of my time trying to work on the Processing Board, and it seemed to bring back the blue for the longest period. Was this a co-incidence? Am I working in the right area for the blue signal from TV and inputs?
If anyone could provide any guidance I would be very grateful, as I love this TV and it is way too good to replace just yet.
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