Philips 41JP20 still shuts down

[James Sweet]

I messed with this thing some more and am still stuck. Press the power
button and the green light comes on, HV comes up, about a second later the
relay clicks and the PSU shuts down. Power light remains on and the other
two LED's illuminate. Remote (which I think was working before) doesn't turn
the set on or off.

So far I've:

Replaced arcing flyback, that got the set up and running briefly but I
turned it off to reassemble and then it started this shutdown thing

Resoldered entire power board

Resoldered most of the sweep board

Resoldered yoke interconnect board

Checked all the diodes, transistors, and fusible resistors on both the power
board and sweep board

Measured voltages out of the power supply including HV, all appear within
spec for the ~1 sec it'll stay powered on

Grumbled, cursed at it and brooded


I'm wondering if I should just hope to find a known good chassis for it?
Someone told me it's a PTV300.

 

[techforce]

I was told the ABL Pin on the FBT can trigget Shutdown in a TV or Monitor.
Does this set have an ABL Pin and related Circuitry? Sometimes there a TRIP
Pot to set.


| I messed with this thing some more and am still stuck. Press the power
| button and the green light comes on, HV comes up, about a second later the
| relay clicks and the PSU shuts down. Power light remains on and the other
| two LED's illuminate. Remote (which I think was working before) doesn't
turn
| the set on or off.
|
| So far I've:
|
| Replaced arcing flyback, that got the set up and running briefly but I
| turned it off to reassemble and then it started this shutdown thing
|
| Resoldered entire power board
|
| Resoldered most of the sweep board
|
| Resoldered yoke interconnect board
|
| Checked all the diodes, transistors, and fusible resistors on both the
power
| board and sweep board
|
| Measured voltages out of the power supply including HV, all appear within
| spec for the ~1 sec it'll stay powered on
|
| Grumbled, cursed at it and brooded
|
|
| I'm wondering if I should just hope to find a known good chassis for it?
| Someone told me it's a PTV300.
|
|
|

 

[Ol' Duffer]

Replaced arcing flyback, that got the set up and running briefly but I
turned it off to reassemble and then it started this shutdown thing

I'm wondering if I should just hope to find a known good chassis for it?
Someone told me it's a PTV300.

PTV330 to be exact, but the distinction amounts to frills like high
power stereo sound that are almost surely unrelated to your problem.
Used to see these all the time, not so much anymore. 'Bout 15 years
old y'know. So okay, I have a little free time and I'll try to help.

Grounds:
I'll assume you've found your hot ground and cold ground test points
on the power board (the one with the flyback). If not;
TP1 = cold ground
TP3 = hot ground

Main Power Supplies:
Verify 130V (hot) supply at TP7/TP3, also on collector of Q14,
not very critical at this point, anything within a few volts will
probably work.
Verify approximately 120V (hot) on Q14 output, easier to clip onto
R69 the big power resistor standing up. Actual voltage will vary,
I usually see about 118V on working sets.
If the above measurements are true, the regulator is working and
you have a horizontal drive signal.

HV Reference:
Now check the +210 (cold) EHT reference TP14/TP1. I expect to see
about 180V here on a properly working set, and that is what I use
as my initial target if I have to re-adjust. If this looks high,
it may be the cause of your shutdown. Here's the deal, high voltage
is regulated by feedback from a tertiary winding on the hot side
TP15/TP3, but over-voltage is detected by a different tertiary
winding on the cold side TP14/TP1, so replacing the flyback changes
this relationship and often causes unnecessarily touchy shutdown.
They were sometimes overly touchy from the factory anyway. The
over-voltage detection circuit is on the other (deflection) board,
but since your main failure appears to have been the flyback, you
may not have to mess with the other board.

If you determine that the HV regulator needs to be turned down,
locate RP2. It's under one of the metal cans that look like IF
transformers, but have no holes. The cans are installed by the
factory to prevent anyone from messing with their adjustments.
These parts of the schematic (including the flyback) are marked
"non-serviceable area". I like to leave the can off so that the
next guy (who may or may not be me) will know the pot has been
tweaked.

Seems like a good place to pause for questions, or may be all
you need to know. If not, post some more and I can try to walk
you through the shutdown circuits.

 

[James Sweet]

Main Power Supplies:
Verify 130V (hot) supply at TP7/TP3, also on collector of Q14,
not very critical at this point, anything within a few volts will
probably work.
Verify approximately 120V (hot) on Q14 output, easier to clip onto
R69 the big power resistor standing up. Actual voltage will vary,
I usually see about 118V on working sets.
If the above measurements are true, the regulator is working and
you have a horizontal drive signal.

HV Reference:
Now check the +210 (cold) EHT reference TP14/TP1. I expect to see
about 180V here on a properly working set, and that is what I use
as my initial target if I have to re-adjust. If this looks high,
it may be the cause of your shutdown. Here's the deal, high voltage
is regulated by feedback from a tertiary winding on the hot side
TP15/TP3, but over-voltage is detected by a different tertiary
winding on the cold side TP14/TP1, so replacing the flyback changes
this relationship and often causes unnecessarily touchy shutdown.
They were sometimes overly touchy from the factory anyway. The
over-voltage detection circuit is on the other (deflection) board,
but since your main failure appears to have been the flyback, you
may not have to mess with the other board.

If you determine that the HV regulator needs to be turned down,
locate RP2. It's under one of the metal cans that look like IF
transformers, but have no holes. The cans are installed by the
factory to prevent anyone from messing with their adjustments.
These parts of the schematic (including the flyback) are marked
"non-serviceable area". I like to leave the can off so that the
next guy (who may or may not be me) will know the pot has been
tweaked.

So after the chaos of moving settled down I was *finally* able to get to
this. Removing the cans which I had assumed were transformers I found the
adjustment pots and discovered that turning down the HV does indeed fix the
shutdown, it's still quite touchy though. Before I dig too deep, what should
the HV be on a properly running set? Or should I just measure the HV
reference? There doesn't appear to be an adjustment for the shutdown as many
sets have, what modification do I need to make to make it less sensitive?
I'm assuming a resistor change but not having a schematic makes it
difficult.

Once this is all done I get to experience the joys of a full calibration, I
dread doing the convergence on PTV's, still amazes me they can have them
looking so good from the factory.

 

[Ol' Duffer]

So after the chaos of moving settled down I was *finally* able to get to
this. Removing the cans which I had assumed were transformers I found the
adjustment pots and discovered that turning down the HV does indeed fix the
shutdown, it's still quite touchy though. Before I dig too deep, what should
the HV be on a properly running set? Or should I just measure the HV
reference?

The service manual doesn't say what the actual HV is
supposed to be, but it's "real high" (40KV+?) and they
(deliberately?) don't provide a place where you can
measure it. And I seriously don't recommend trying to
poke through insulation anywhere to get at it.

I go by the EHT reference on TP14 (cold), and expect
to see about 180VDC. Again, the factory doesn't give
an exact number or a procedure, this is just what I
have seen on normally behaving sets.

Their approach was "module replacement" when they built
these, and they witheld a lot of information about what
were essentially easily-repaired boards.

There doesn't appear to be an adjustment for the shutdown as many
sets have, what modification do I need to make to make it less sensitive?

It's on the other board (deflection). Look for RP1 under
another one of those cans. The EHT reference is dropped
through R39, then RP1, then R40 to ground. The wiper of
RP1 goes through a Zener diode Z3 to the base of Q3, which
is the over-voltage sensor. Z3 has been known to become
leaky, and the factory tech didn't tell me it was a 6.2V
1/2W (wink). If you're sure the HV isn't out of control,
you can short the base of Q3 to ground and run the HV up
and down to eliminate other stuff.

There are some other things that can cause shutdown, but
this is the most common area for "touchy".

I'm assuming a resistor change but not having a schematic makes it
difficult.

Is your hotmail address valid (wink)?

Once this is all done I get to experience the joys of a full calibration, I
dread doing the convergence on PTV's, still amazes me they can have them
looking so good from the factory.

Fortunately, the controls pretty much do what they say.
If they haven't been messed with, it may not need much.

 

[James Sweet]

The service manual doesn't say what the actual HV is
supposed to be, but it's "real high" (40KV+?) and they
(deliberately?) don't provide a place where you can
measure it. And I seriously don't recommend trying to
poke through insulation anywhere to get at it.

I go by the EHT reference on TP14 (cold), and expect
to see about 180VDC. Again, the factory doesn't give
an exact number or a procedure, this is just what I
have seen on normally behaving sets.

Their approach was "module replacement" when they built
these, and they witheld a lot of information about what
were essentially easily-repaired boards.
sensitive?

It's on the other board (deflection). Look for RP1 under
another one of those cans. The EHT reference is dropped
through R39, then RP1, then R40 to ground. The wiper of
RP1 goes through a Zener diode Z3 to the base of Q3, which
is the over-voltage sensor. Z3 has been known to become
leaky, and the factory tech didn't tell me it was a 6.2V
1/2W (wink). If you're sure the HV isn't out of control,
you can short the base of Q3 to ground and run the HV up
and down to eliminate other stuff.

There are some other things that can cause shutdown, but
this is the most common area for "touchy".


Is your hotmail address valid (wink)?


Fortunately, the controls pretty much do what they say.
If they haven't been messed with, it may not need much.

Thanks a bunch for all the info, this should be all I need to have this
thing finished. I'm quite sure the convergence and color ballance will need
a full going over as I had all three CRT's out to change the coolant just a
couple weeks before the flyback burned up. Fortunatly I have the sheet that
details the setup procedure and I have a video CD I made with some basic
test patterns (a shame they don't even provide a built in crosshatch
generator like some older PTV's I've dealt with) so I think with some
patience it should be looking pretty good.

It sat dead for several years before it was given to me and I had it for
almost 3 years before I had a chance to repair the power supply so the CRT's
themselves are in remarkably good condition for the age. Seems once I
brought it back to life just about everything else that can go wrong with it
did.