Philips tv with no picture or disapearing picture or slow picture startup but good sound??

Do you have a question? Post it now! No Registration Necessary

Translate This Thread From Swedish to

Threaded View
Hi all

I have a Philips 28ml8805 (FL1.6 or near) with a strange and hard to
find problem. The unit is a slow starter which mean that it takes up to
20min to get picture while the sound is comming on after 5s. Sometimes
the picture comes after 15s but goes away again after som sec and then
it takes several minutes to reappear. The picture is real good (when on)
and no mechanical respons from all circuitbords.

No problems with the 200v, 141v, 5v, 8v, 13v, 16.5v, the only voltage
thats diff a little is 17.5v is 19.5v. I have changed the tda4680 in an
atempt to se if it was the cause of the fault but no diff.
I think i have checked all resistors around this circuit and found no
fault in them, i have resoldered all components in the HOT area and some
outside it also, no reaction on the fault.

I have seen some that have this problems also on the net but no answer
to what it is. I suspect the CRT but thats no option to change, the odd
thing is that the picture is WERY good on this unit when working so this
would oppose the theori that it is the CRT that are the fault.

Is there some that have a clue to whats wrong with this unit?

Janne G

Re: Philips tv with no picture or disapearing picture or slow picture startup but good sound??
ESR the filter caps around the Flyback and in SMPS or just replace them.

kip



Re: Philips tv with no picture or disapearing picture or slow picture startup but good sound??
Quoted text here. Click to load it

While I've never worked on a Philips TV, I do have some suggestions.

Check your voltages that go to the tube, i.e. G2, etc.  See if the
filments are lit up, see if the tube is getting what it needs to work
in other words.

How does the pic come on, does it fade in or just pop on with full
brightness and good color?

If you have the voltages, then you're going to need to trace the
video/deflection path and see where it goes awry.  I said deflection
because you could also have vertical collapse, although many sets will
turn off if they detect that problem.

Re: Philips tv with no picture or disapearing picture or slow picture startup but good sound??
How is the picture with a vcr connected by a scartcable.

If the picture is there right away, suspect the tunerpart. If so the tuner
has possible some electrolytic capacitors inside which are leaking. Check
the pcb traces for interrupts made by the leakage.

Greetings Peter

Quoted text here. Click to load it


---
Outgoing mail is certified Virus Free. By avg anti virus system
Checked by AVG anti-virus system (http://www.grisoft.com ).
We've slightly trimmed the long signature. Click to see the full one.
Re: Philips tv with no picture or disapearing picture or slow picture startup but good sound??
Quoted text here. Click to load it

A few ideas:

I've seen this symptom on a cp110 chassis - had to replace the 22uF
250v caps in the high voltage line from the power supply - if you
already have done, you might want to try doing it again to be sure, as
you could have a duff cap.

Remove the neckboard from the tube and clean all the contacts there.
In the past, philips had some bad sockets.

I assume you have resoldered the CRT heater leads on the mainboard and
neckboard?

check: RGB blanking circuit and associated RGB cap?

Sorry can't be more precise with your model!
-B

Re: Philips tv with no picture, SOLVED, nearly
Quoted text here. Click to load it

I had some sleepless nights over this but i find a way to get to the
"kern"(bottom) of the problem with a plastic pin that insulated me from
the high voltage of the CRT and "friends".

It was a "jumper" (SMD shortcut) that was loose near the horisontal
powercircuit tda3654 or someting (the one thats get really hot) that had
  poor soldering. I did not see anything in the microscope when examine
it but the measurement did say that it was a problem there. I've
resoldered it and now the startuptime is down to around 2.5 min for a
picture, and yes, it is much but i guess that the CRT have got some
damage when testing this fault and now have a relativly large diff
between the R G B cannons and therefore the 4680 think it isn't ready to
turn on the video to the CRT before that time. The picture is WERY good
when working so i just have to accept the long startup time because i
can't find any more problems with the unit when examine it deeply.

If some have the same problem i can give the the exact componenet name
if you whant, contact me by mail then, hopefully decipering of my
mailadress would not be that difficult.

Anyone that have any moore sudgestions to the startuptime?

Thanks for all the sudgestions i have got on this problem.

Site Timeline