Mad to fix STB?

M

Mark Kelep

Guest
Hi,
I have a mate who has a Wide screen SD TFT TV, but wont be convinced of any
benefit by getting a digital STB, yep he's still using the old reception and
it looks shabby.
It cant even seem to get wide screen format (not sure if that's the only
reason why though)
Anyway, my old Teac DV-B420 slowly shit itself, frozen screen, wouldn't
respond to remote or front panel commands unless I plugged it out (including
aerial) then it did work until it became so slack wit these re-boots that I
bought a new one.
But After looking in the old unit, it was clear that the eight pin chip had
been getting bloody hot so I wonder if I can fix this thing and give it to
Timmy the slackarse mate, for nothing.
See Pic here.
www.spleena.com.au
there's no add crap here, I just dont have any other way to put a pic up
yet.
Thanks
Mark
 
On Sat, 09 Feb 2008 11:35:42 GMT, "Mark Kelep"
<mxarvkkezlly2@biagpboncd.com> put finger to keyboard and composed:

Hi,
I have a mate who has a Wide screen SD TFT TV, but wont be convinced of any
benefit by getting a digital STB, yep he's still using the old reception and
it looks shabby.
It cant even seem to get wide screen format (not sure if that's the only
reason why though)
Anyway, my old Teac DV-B420 slowly shit itself, frozen screen, wouldn't
respond to remote or front panel commands unless I plugged it out (including
aerial) then it did work until it became so slack wit these re-boots that I
bought a new one.
But After looking in the old unit, it was clear that the eight pin chip had
been getting bloody hot so I wonder if I can fix this thing and give it to
Timmy the slackarse mate, for nothing.
See Pic here.
www.spleena.com.au
there's no add crap here, I just dont have any other way to put a pic up
yet.
Thanks
Mark
Click to expand...
Even though they look OK, I would change C2 on the AC side and the
small electrolytics on the DC side. I'd also scrape the copper tracks
around U1 and build them up with solder and wire links. Check the caps
on the main PCB as well. I don't know whether others would agree, but
I'd remove the glue from around the optocoupler at U2. Too many times
I've encountered glue that has become conductive and corrosive, so I'm
uncomfortable seeing any glue bridging the AC and DC sides of your
PCB.

Here is the datasheet for the NCP1200-60:
http://www.onsemi.com/pub/Collateral/NCP1200-D.PDF

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
 
"Mark Kelep"

But After looking in the old unit, it was clear that the eight pin chip
had been getting bloody hot so I wonder if I can fix this thing and give
it to Timmy the slackarse mate, for nothing.
See Pic here.
www.spleena.com.au
Click to expand...

** The SMPS IC is an NCP 1200 from On Semi.

http://www.onsemi.com/pub/Collateral/NCP1200-D.PDF

The app notes indicate it runs damn hot when operated from a 240 volt, AC
supply.

The internal ( switching ? ) voltage regulator runs from the rectified AC -
about 340 volts and draws around 1.8 mA

An 8 pin DIP dissipating 600mW continuously will darken a phenolic PCB.

If the DC rail tests OK on a DMM and scope - then it ain't your problem.



....... Phil
 
"Phil Allison" <philallison@tpg.com.au> wrote in message
news:6176a3F1u4pobU1@mid.individual.net...
"Mark Kelep"

But After looking in the old unit, it was clear that the eight pin chip
had been getting bloody hot so I wonder if I can fix this thing and give
it to Timmy the slackarse mate, for nothing.
See Pic here.
www.spleena.com.au


** The SMPS IC is an NCP 1200 from On Semi.

http://www.onsemi.com/pub/Collateral/NCP1200-D.PDF

The app notes indicate it runs damn hot when operated from a 240 volt, AC
supply.

The internal ( switching ? ) voltage regulator runs from the rectified
C - about 340 volts and draws around 1.8 mA

An 8 pin DIP dissipating 600mW continuously will darken a phenolic PCB.

If the DC rail tests OK on a DMM and scope - then it ain't your problem.



...... Phil
Click to expand...
Thanks for the replies, the board certainly does have that familiar burnt
stink thats for sure.

I checked all output voltages with a CRO and DMM.
Where it should have been 12vdc it was, with no ripple.
However where it should be 5vdc, it was 5.75vdc (still no ripple) and
finally what should have measured 3v3 (3.3v?), it was only 3.05vdc with no
ripple.
All was measured with unit in standby mode and on (yes it still starts up
sometimes) with very little diff. in either mode.
I should mention that when connected up to TV, diagonal interference lines
are noticable but only when screen is mainly white. It never used to be like
that.
I haven't changed any caps yet btw.
Any other ideas would be great, before I chuck it.

Thanks again
Mark
 
On Sun, 10 Feb 2008 07:24:37 GMT, "Mark Kelep"
<mxarvkkezlly2@biagpboncd.com> put finger to keyboard and composed:

I checked all output voltages with a CRO and DMM.
Where it should have been 12vdc it was, with no ripple.
Click to expand...
Could that be because this rail is derived from a 7812 regulator
(located above C7)?

However where it should be 5vdc, it was 5.75vdc (still no ripple) and
finally what should have measured 3v3 (3.3v?), it was only 3.05vdc with no
ripple.
Click to expand...
I suspect that the +5V rail is the one that is being regulated via the
optocoupler at U2 and the TL431 (?) at U4. If so, then I'd replace the
+5V capacitor (and all the others).

All was measured with unit in standby mode and on (yes it still starts up
sometimes) with very little diff. in either mode.
I should mention that when connected up to TV, diagonal interference lines
are noticable but only when screen is mainly white. It never used to be like
that.
I haven't changed any caps yet btw.
Any other ideas would be great, before I chuck it.

Thanks again
Mark
Click to expand...
- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
 
On Sat, 09 Feb 2008 11:35:42 GMT, "Mark Kelep" <mxarvkkezlly2@biagpboncd.com>
wrote:

:Hi,
:I have a mate who has a Wide screen SD TFT TV, but wont be convinced of any
:benefit by getting a digital STB, yep he's still using the old reception and
:it looks shabby.
:It cant even seem to get wide screen format (not sure if that's the only
:reason why though)
:Anyway, my old Teac DV-B420 slowly shit itself, frozen screen, wouldn't
:respond to remote or front panel commands unless I plugged it out (including
:aerial) then it did work until it became so slack wit these re-boots that I
:bought a new one.
:But After looking in the old unit, it was clear that the eight pin chip had
:been getting bloody hot so I wonder if I can fix this thing and give it to
:Timmy the slackarse mate, for nothing.
:See Pic here.
:www.spleena.com.au
:there's no add crap here, I just dont have any other way to put a pic up
:yet.
:Thanks
:Mark
:
:
:


Apart from suggestions by Phil and Franc, some of those electros at the top
right of the pic look a little suspicious (bulging top), so I would be ESR
testing or just replacing them. While your oscilloscope testing on stand-by
seems ok the real test should have been performed while operating at full load.

As far as the darkened pcb caused by the controller IC, I haven't seen that
problem before, but I haven't encountered that particular IC device yet. On the
more common UC384x series I have never seen it unless the IC is severely
overloaded. I would replace it anyway.
 
"Franc Zabkar" <fzabkar@iinternode.on.net> wrote in message
news:4mouq3pekurj45u1h2h7jii3hqt1at1rok@4ax.com...
On Sun, 10 Feb 2008 07:24:37 GMT, "Mark Kelep"
mxarvkkezlly2@biagpboncd.com> put finger to keyboard and composed:

I checked all output voltages with a CRO and DMM.
Where it should have been 12vdc it was, with no ripple.

Could that be because this rail is derived from a 7812 regulator
(located above C7)?
Click to expand...
* Sure is

However where it should be 5vdc, it was 5.75vdc (still no ripple) and
finally what should have measured 3v3 (3.3v?), it was only 3.05vdc with no
ripple.

I suspect that the +5V rail is the one that is being regulated via the
optocoupler at U2 and the TL431 (?) at U4. If so, then I'd replace the
+5V capacitor (and all the others).
Click to expand...
* U4 is a TL 431 yes!
There is no obvious bulging on any of the caps but i'll change them and see
what happens.

Thanks again
Mark

(remove x v z and a b c)
 
On Feb 9, 10:35 pm, "Mark Kelep" <mxarvkkezl...@biagpboncd.com> wrote:
Hi,
I have a mate who has a Wide screen SD TFT TV, but wont be convinced of any
benefit by getting a digital STB, yep he's still using the old reception and
it looks shabby.
Click to expand...
At under $30 for an SD STB these days, it's a no-brainer!
Seeing will be believing.

Dave.
 
"David L. Jones" <altzone@gmail.com> wrote in message
news:f44b840e-23da-4a55-b4c7-77e80f22f85c@d21g2000prf.googlegroups.com...
On Feb 9, 10:35 pm, "Mark Kelep" <mxarvkkezl...@biagpboncd.com> wrote:
Hi,
I have a mate who has a Wide screen SD TFT TV, but wont be convinced of
any
benefit by getting a digital STB, yep he's still using the old reception
and
it looks shabby.

At under $30 for an SD STB these days, it's a no-brainer!
Seeing will be believing.

Dave.
Click to expand...
Yeah yeah, it was only a matter of time before someone responded with that
one in this 'throw away' world.
I reckon i'll wait a bit longer and replace a few caps etc before I add to
the land fill though

Mark.
 
"Ross Herbert" <rherber1@bigpond.net.au> wrote in message
news:fk8vq3967p7ftge6csu6r9i5hbi5tfigg0@4ax.com...
On Sat, 09 Feb 2008 11:35:42 GMT, "Mark Kelep"
mxarvkkezlly2@biagpboncd.com
wrote:

:Hi,
:I have a mate who has a Wide screen SD TFT TV, but wont be convinced of
any
:benefit by getting a digital STB, yep he's still using the old reception
and
:it looks shabby.
:It cant even seem to get wide screen format (not sure if that's the only
:reason why though)
:Anyway, my old Teac DV-B420 slowly shit itself, frozen screen, wouldn't
:respond to remote or front panel commands unless I plugged it out
(including
:aerial) then it did work until it became so slack wit these re-boots that
I
:bought a new one.
:But After looking in the old unit, it was clear that the eight pin chip
had
:been getting bloody hot so I wonder if I can fix this thing and give it
to
:Timmy the slackarse mate, for nothing.
:See Pic here.
:www.spleena.com.au
:there's no add crap here, I just dont have any other way to put a pic up
:yet.
:Thanks
:Mark
:
:
:


Apart from suggestions by Phil and Franc, some of those electros at the
top
right of the pic look a little suspicious (bulging top), so I would be ESR
testing or just replacing them. While your oscilloscope testing on
stand-by
seems ok the real test should have been performed while operating at full
load.

As far as the darkened pcb caused by the controller IC, I haven't seen
that
problem before, but I haven't encountered that particular IC device yet.
On the
more common UC384x series I have never seen it unless the IC is severely
overloaded. I would replace it anyway.
Click to expand...
Finally got around to replacing caps (as many as I could from spares I had
lying around) and it's now working as good as it ever did.
Thanks to those with the very helpful advice.

Mark
 
Mark Kelep wrote:
Anyway, my old Teac DV-B420 slowly shit itself, frozen screen, wouldn't
respond to remote or front panel commands unless I plugged it out (including
aerial) then it did work until it became so slack wit these re-boots that I
bought a new one.
But After looking in the old unit, it was clear that the eight pin chip had
been getting bloody hot so I wonder if I can fix this thing and give it to
Timmy the slackarse mate, for nothing.
See Pic here.
www.spleena.com.au
Click to expand...
Nice picture. My STB looks similar though I have a hole where most of
the chip used to be! Did you replace this chip? Are they easy enough to
get hold of?

I liked this STB as it had a SCART connector so I would like to get it
going again if possible.


---
Michael
 
"Michael Traub" <m1chayeeell@strawb.idee.au> wrote in message
news:47bad9fb$1@dnews.tpgi.com.au...
Mark Kelep wrote:
Anyway, my old Teac DV-B420 slowly shit itself, frozen screen, wouldn't
respond to remote or front panel commands unless I plugged it out
(including aerial) then it did work until it became so slack wit these
re-boots that I bought a new one.
But After looking in the old unit, it was clear that the eight pin chip
had been getting bloody hot so I wonder if I can fix this thing and give
it to Timmy the slackarse mate, for nothing.
See Pic here.
www.spleena.com.au

Nice picture. My STB looks similar though I have a hole where most of the
chip used to be! Did you replace this chip? Are they easy enough to get
hold of?

I liked this STB as it had a SCART connector so I would like to get it
going again if possible.


---
Michael
Click to expand...
Hi, Michael, I thought this thread was pretty much finished and was about to
get that pic off my site.
I didnt replace the chip, what Phil said made sense in that chip does get
hot and will show signs of that fact with a phenolic board.
So I took the advice of the other kind people and simply replaced a few caps
as recommended.
As you have read, all is now well.
Farnell claimed they stock the 1200P60 from 'ON Semiconductor' but theyhad
none in stock.
I'm sure RS or WES, would be another possible source.
However, from what i've learnt (being a DYI like you) replace as many electo
caps as you can if you do get hold of the chip.
It's very likely that something caused the chip to blow it's arse off.
It is also likely that your situation is worse that mine was.
I can understand why might miss the SCART too, I found that my new one
doesnt even have optical out either, so there you go.
Still worth fixing if you can do it cheap enough, but know where to draw the
line, otherwise Dave will have a chuckle, and we cant have that.
Cheers,
Mark

get rid of x v z a b c from my address to reply
 
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