P
Peter Duck
A roughly ten-year-old Thorn CT514TN using this chassis does everything
it should except display a picture, whether 'on-air' or from the AV
inputs.
Sound is OK, as is the on-screen display of menus, etc, and it seems to
respond to all commands, including channel-changes.
The problem appears to be that pin21 on the jungle-chip, which should be
at <0.4v, is internally pulled up to about 4.6v (from a supply-voltage,
Vcc, of 8.0) despite a 1K resistor to ground, even when nothing else is
connected to it.
According to a 1994 TDA8362 data-sheet, a voltage between 0.9 and a
maximum of 3.0 will blank the picture (no mention of OSD, which is alive
and well).
Seems a pretty clear-cut case of chip-failure (all supply-voltages are
OK), but obtaining a replacement isn't proving straightforward ...
- On a CP365 circuit diagram (undated) the chip is shown as TDA8362, but
the actual one present is TDA8362B
- My Googling hasn't found any data on other versions than the original
8362, now billed as 'obsolete' on Philips' website.
- I've found several UK suppliers of the 8362, and of 'minidip' versions
with suffixes like EN4, but not of a 8362B.
I'm therefore left with the questions
- What's the difference between the 8362 and the 8362B?
(or "Where can I find data on the latter?")
- Does it matter on this chassis/in this set?
it should except display a picture, whether 'on-air' or from the AV
inputs.
Sound is OK, as is the on-screen display of menus, etc, and it seems to
respond to all commands, including channel-changes.
The problem appears to be that pin21 on the jungle-chip, which should be
at <0.4v, is internally pulled up to about 4.6v (from a supply-voltage,
Vcc, of 8.0) despite a 1K resistor to ground, even when nothing else is
connected to it.
According to a 1994 TDA8362 data-sheet, a voltage between 0.9 and a
maximum of 3.0 will blank the picture (no mention of OSD, which is alive
and well).
Seems a pretty clear-cut case of chip-failure (all supply-voltages are
OK), but obtaining a replacement isn't proving straightforward ...
- On a CP365 circuit diagram (undated) the chip is shown as TDA8362, but
the actual one present is TDA8362B
- My Googling hasn't found any data on other versions than the original
8362, now billed as 'obsolete' on Philips' website.
- I've found several UK suppliers of the 8362, and of 'minidip' versions
with suffixes like EN4, but not of a 8362B.
I'm therefore left with the questions
- What's the difference between the 8362 and the 8362B?
(or "Where can I find data on the latter?")
- Does it matter on this chassis/in this set?
