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From: William Sommerwerck on 9 May 2010 11:22
> It turned out to be a 40-pin proprietary chip that decided to fail.
> I found this out by warming up the whole board with hot air until
> vertical sync stabilized. Selective application of cold spray
> pinpointed the chip.

"Heh, heh, heh", he muttered smugly.

Out of curiosity, what exactly was the chip's function or funtions?


From: stratus46 on 9 May 2010 13:59
On May 9, 8:22 am, "William Sommerwerck" <grizzledgee...(a)comcast.net>
wrote:
> > It turned out to be a 40-pin proprietary chip that decided to fail.
> > I found this out by warming up the whole board with hot air until
> > vertical sync stabilized. Selective application of cold spray
> > pinpointed the chip.
>
> "Heh, heh, heh", he muttered smugly.
>
> Out of curiosity, what exactly was the chip's function or funtions?

OK, you made the 2%. Semiconductor failure are far less frequent
compared to 'lytic caps. Personally I'd change all the lytics around
the chip before changing the chip. They're easier to get, cheaper,
more likely to fail and if more than 5 years old will probably need to
go anyway. You have it open....

G²
From: lsmartino on 9 May 2010 14:04
On 9 mayo, 11:15, Boris Mohar <borism_vo...(a)sympatico.ca> wrote:
> On Sat, 8 May 2010 16:53:58 -0700 (PDT), stratu...(a)yahoo.com wrote:
> >On May 8, 11:43 am, "Lance Dyer" <nipperchip...(a)hotmail.com> wrote:
> > > Bad caps
>
> > > "William Sommerwerck" <grizzledgee...(a)comcast.net> wrote in message
>
> > >news:hs48s8$kgg$1(a)news.eternal-september.org...
>
> > > > On modern sets, vertical sync is generated from the horizontal
> >sync. The
> > > > chip that handles sync separation is a likely possibility.
>
> > > > It's also possible the bias on the vertical output stage is
> >drifting.
>
> >I second the bad caps suggestion. I put the odds at 98% dried out
> >cap(s). The 'warm up' description is exactly how 'lytics behave. they
> >always measure better after unsoldering. I just changed 72 caps in
> >Sony digital Betacam machines this morning.
>
> >The 'vertical from horizontal' description is pretty poor. Vertical
> >like horizontal is part of the composite sync. First sync is recovered
> >from the video and then processed to extract the H and V components.
> >This can be done with counters and PLLs or simple RC networks.
>
> >G²
>
> It turned out to be a 40pin proprietary chip that decided to fail. I found
> this out by waning up the whole board with hot air until vertical sync
> stabilized.  Selective application of cold spray pinpointed the chip.  I wish
> that it was the caps.  Not having the replacement handy I glued a jacket of
> thermal insulation over the chip hoping that it warms up sooner.  Seems
> shorten the "warmup" time.
>
> --
> Boris- Ocultar texto de la cita -
>
> - Mostrar texto de la cita -

I don´t know, but I can´t remember a case where a semiconductor
improved after warming. Usually is in reverse: a damaged semiconductor
will work while it´s cold and start to fail as soon as it heats. If
you see any electrolytic capacitors in the vecinity of the chip,
replace them first. Electrolitycs are cheap and easy to replace, and
probaly will solve the fault.
From: Boris Mohar on 9 May 2010 15:43
On Sun, 9 May 2010 08:22:14 -0700, "William Sommerwerck"
<grizzledgeezer(a)comcast.net> wrote:

>> It turned out to be a 40-pin proprietary chip that decided to fail.
>> I found this out by warming up the whole board with hot air until
>> vertical sync stabilized. Selective application of cold spray
>> pinpointed the chip.
>
>"Heh, heh, heh", he muttered smugly.
>
>Out of curiosity, what exactly was the chip's function or funtions?
>

Right now it is a thermometer;

--
Boris
From: Chuck on 10 May 2010 10:10
On Sun, 9 May 2010 11:04:46 -0700 (PDT), lsmartino
<luismartino76(a)gmail.com> wrote:

>On 9 mayo, 11:15, Boris Mohar <borism_vo...(a)sympatico.ca> wrote:
>> On Sat, 8 May 2010 16:53:58 -0700 (PDT), stratu...(a)yahoo.com wrote:
>> >On May 8, 11:43�am, "Lance Dyer" <nipperchip...(a)hotmail.com> wrote:
>> > > Bad caps
>>
>> > > "William Sommerwerck" <grizzledgee...(a)comcast.net> wrote in message
>>
>> > >news:hs48s8$kgg$1(a)news.eternal-september.org...
>>
>> > > > On modern sets, vertical sync is generated from the horizontal
>> >sync. The
>> > > > chip that handles sync separation is a likely possibility.
>>
>> > > > It's also possible the bias on the vertical output stage is
>> >drifting.
>>
>> >I second the bad caps suggestion. I put the odds at 98% dried out
>> >cap(s). The 'warm up' description is exactly how 'lytics behave. they
>> >always measure better after unsoldering. I just changed 72 caps in
>> >Sony digital Betacam machines this morning.
>>
>> >The 'vertical from horizontal' description is pretty poor. Vertical
>> >like horizontal is part of the composite sync. First sync is recovered
>> >from the video and then processed to extract the H and V components.
>> >This can be done with counters and PLLs or simple RC networks.
>>
>> >G�
>>
>> It turned out to be a 40pin proprietary chip that decided to fail. I found
>> this out by waning up the whole board with hot air until vertical sync
>> stabilized. �Selective application of cold spray pinpointed the chip. �I wish
>> that it was the caps. �Not having the replacement handy I glued a jacket of
>> thermal insulation over the chip hoping that it warms up sooner. �Seems
>> shorten the "warmup" time.
>>
>> --
>> Boris- Ocultar texto de la cita -
>>
>> - Mostrar texto de la cita -
>
>I don�t know, but I can�t remember a case where a semiconductor
>improved after warming. Usually is in reverse: a damaged semiconductor
>will work while it�s cold and start to fail as soon as it heats. If
>you see any electrolytic capacitors in the vecinity of the chip,
>replace them first. Electrolitycs are cheap and easy to replace, and
>probaly will solve the fault.


Once you replace the lytics give the board a good scrub. Fluid which
has leaked from the caps will cause this problem after all the caps
are replaced. The resistance of this liquid will change with the
ambient temperature. Chuck
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