I'm developing a love / hate relationship with SMD devices. I love
them when they work, and even when a parts list is available. When
they don't, and one isn't, they cause a lot of grief.

This particular project is a Sceptre X9g Komodo VII A monitor. This
is a 19" LCD monitor. I'm the second person on the project. The
first earned my admiration by reassembling the monitor after pulling
the power supply / inverter. He even left all the screws in the
appropriate holes!!

After reassembling the monitor for test purposes I discovered it
briefly (about 1 second) dimly flashed something on the screen, then
blanked it. After some exploration, I located a bad solder joint on a
film capacitor in the inverter. Resoldering this didn't fix it, it
seems two transistors are shorted base-emitter. For what it's worth,
this design is similar to the inverter used on Dell E172FPb and
E173FPb monitors. A significant difference, the Dell uses through
hole transistors (2SC5707), the Sceptre uses SMD devices.

The transistors are in a package equivalent to a Sanyo PCP
http://datasheet.digchip.com/413/413...-0-2SD2099.pdf The
transistors have identification that looks somethng like this:

DK
o_
QH

I suspect that these markings identify the manufacturer, the
manufacturer's code for the particular component, and possibly a date
code. Needless to say, none of the SMD identification lists show a
device using either of these codes in a similar package. I started
with Sanyo because they make the transistors used in the Dell monitors
mentioned above. Unfortunately, while Sanyo DOES use the DK code on
their PCP package, the datadheet indicates this is a recent addition
to their product line; this monitor was built in 2005.

Using the 2SC5707 I have been able to make an approximate
determination of the characteristics I am looking for, but searches
are handicapped by the myriad packages used by various manufacturers.

Any suggestions would be much appreciated.

PlainBill

On Thu, 24 Sep 2009 11:32:39 -0700, put finger
to keyboard and composed:

The transistors are in a package equivalent to a Sanyo PCP
http://datasheet.digchip.com/413/413...-0-2SD2099.pdf The
transistors have identification that looks somethng like this:

DK
o_
QH

Sanyo PCP1201:
http://www.semiconductor-sanyo.com/ds_e/ENA1164.pdf
http://pdf.dzsc.net.cn/20090227/200902171141512888.pdf
http://www.semiconductor-sanyo.com/s...6&prod=PCP1201

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

On Fri, 25 Sep 2009 06:59:58 +1000, Franc Zabkar
wrote:

On Thu, 24 Sep 2009 11:32:39 -0700, put finger
to keyboard and composed:

The transistors are in a package equivalent to a Sanyo PCP
http://datasheet.digchip.com/413/413...-0-2SD2099.pdf The
transistors have identification that looks somethng like this:

DK
o_
QH

Sanyo PCP1201:
http://www.semiconductor-sanyo.com/ds_e/ENA1164.pdf
http://pdf.dzsc.net.cn/20090227/200902171141512888.pdf
http://www.semiconductor-sanyo.com/s...6&prod=PCP1201

- Franc Zabkar

Frank,

Thanks, I'd already found that information. There are reasons to
believe that is not the proper part.

1. The power supply / inverter circuit board has a 12/01/2003 date on
it; the monitor was built in May, 2005. Sanyo indicates the PCP1201
has a status of 'New'.

2. AFTER posting this appeal I found pictures of two inverters from
Compaq TFT5010 monitors. These use the identical circuit (but a
different layout). One of the inverters has 4 transistors labeled DK
QH. The other has 4 transistors labeled DK QG. My initial conclusion
was the QG / QH is a date code. The QG is used on the same package
for the 2SC6096

Wahoo!!! The package is SOT89. Mouser Electronics' search engine
shows tiny pictures of the components that match your parameters. I
found a PBSS4480X is available in the proper package and appears to
have (superficially) the proper specs. Now to see if the package
markings match.

Thanks,

PlainBill

On Fri, 25 Sep 2009 11:00:15 -0700, put finger
to keyboard and composed:

On Fri, 25 Sep 2009 06:59:58 +1000, Franc Zabkar
wrote:

On Thu, 24 Sep 2009 11:32:39 -0700, put finger
to keyboard and composed:

The transistors are in a package equivalent to a Sanyo PCP
http://datasheet.digchip.com/413/413...-0-2SD2099.pdf The
transistors have identification that looks somethng like this:

DK
o_
QH

Sanyo PCP1201:
http://www.semiconductor-sanyo.com/ds_e/ENA1164.pdf
http://pdf.dzsc.net.cn/20090227/200902171141512888.pdf
http://www.semiconductor-sanyo.com/s...6&prod=PCP1201

- Franc Zabkar

Frank,

Thanks, I'd already found that information. There are reasons to
believe that is not the proper part.

1. The power supply / inverter circuit board has a 12/01/2003 date on
it; the monitor was built in May, 2005. Sanyo indicates the PCP1201
has a status of 'New'.

2. AFTER posting this appeal I found pictures of two inverters from
Compaq TFT5010 monitors. These use the identical circuit (but a
different layout). One of the inverters has 4 transistors labeled DK
QH. The other has 4 transistors labeled DK QG. My initial conclusion
was the QG / QH is a date code. The QG is used on the same package
for the 2SC6096

Wahoo!!! The package is SOT89. Mouser Electronics' search engine
shows tiny pictures of the components that match your parameters. I
found a PBSS4480X is available in the proper package and appears to
have (superficially) the proper specs. Now to see if the package
markings match.

Thanks,

PlainBill

It could be a Sanyo 2SD1628:
http://www.datasheetcatalog.org/data..._e/2SD1628.pdf

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

On Sat, 26 Sep 2009 07:50:55 +1000, Franc Zabkar
wrote:

On Fri, 25 Sep 2009 11:00:15 -0700, put finger
to keyboard and composed:

On Fri, 25 Sep 2009 06:59:58 +1000, Franc Zabkar
wrote:

On Thu, 24 Sep 2009 11:32:39 -0700, put finger
to keyboard and composed:

The transistors are in a package equivalent to a Sanyo PCP
http://datasheet.digchip.com/413/413...-0-2SD2099.pdf The
transistors have identification that looks somethng like this:

DK
o_
QH

Sanyo PCP1201:
http://www.semiconductor-sanyo.com/ds_e/ENA1164.pdf
http://pdf.dzsc.net.cn/20090227/200902171141512888.pdf
http://www.semiconductor-sanyo.com/s...6&prod=PCP1201

- Franc Zabkar

Frank,

Thanks, I'd already found that information. There are reasons to
believe that is not the proper part.

1. The power supply / inverter circuit board has a 12/01/2003 date on
it; the monitor was built in May, 2005. Sanyo indicates the PCP1201
has a status of 'New'.

2. AFTER posting this appeal I found pictures of two inverters from
Compaq TFT5010 monitors. These use the identical circuit (but a
different layout). One of the inverters has 4 transistors labeled DK
QH. The other has 4 transistors labeled DK QG. My initial conclusion
was the QG / QH is a date code. The QG is used on the same package
for the 2SC6096

Wahoo!!! The package is SOT89. Mouser Electronics' search engine
shows tiny pictures of the components that match your parameters. I
found a PBSS4480X is available in the proper package and appears to
have (superficially) the proper specs. Now to see if the package
markings match.

Thanks,

PlainBill

It could be a Sanyo 2SD1628:
http://www.datasheetcatalog.org/data..._e/2SD1628.pdf

- Franc Zabkar
Franc,

That seems VERY likely. Thank you very much!!! This is turning into
a great day!!!

Replace spark plugs in Wife's van (saving $150 over the dealer's
price)

Minnesota beats Northwestern 35 - 24

Find the correct replacement part to repair a monitor.

Thank you very much

PlainBill

On Fri, 25 Sep 2009 06:59:58 +1000, Franc Zabkar
wrote:

On Thu, 24 Sep 2009 11:32:39 -0700, put finger
to keyboard and composed:

The transistors are in a package equivalent to a Sanyo PCP
http://datasheet.digchip.com/413/413...-0-2SD2099.pdf The
transistors have identification that looks somethng like this:

DK
o_
QH

Sanyo PCP1201:
http://www.semiconductor-sanyo.com/ds_e/ENA1164.pdf
http://pdf.dzsc.net.cn/20090227/200902171141512888.pdf
http://www.semiconductor-sanyo.com/s...6&prod=PCP1201

- Franc Zabkar
Frank,

Well, another problem has raised it's ugly head, and I've finally
firmly established the source of these transistors. The Sanyo part
you tentatively identified was unavailable from my US sources. After
some research, I decided a dxt3150-13 would be an acc3eptable
substitute, so I ordered some. Since the original caps in the monitor
were Elite brand (a known 'bad' manufacturer), I ordered replacements
for them from the same distributor. Before placing the order, I
established the monitor would behave in the expected way with the
shorted transistors removed. I also tested the transformer to ensure
it was not defective.

With the shorted transistors installed, the screen would flash dimly
for a few seconds, then go blank. After they were removed, the screen
would come on for a few seconds, then blank. (This is the normal
result of the protection circuits shutting down the inverter because
of insuffficient output). When the replacements arrived, I soldered
in the new transistors and tested it. It worked perfectly for a few
minutes, so I shut it down and began to replace the questionable caps.

After recapping, the intermittent dim flashes returned!!! However,
neither the original nor the replacement transistors are shorted. It
is a puzzlement; I'll be using a scope to see if I can figure out the
problem.

In the meantime, I had received a Viewsonic VX910 monitor. The owner
indicated it was having difficulty turning on, but would eventually
start. Rather than try to verify this, I simply opened up the
monitor, and found three obviously bad caps. These were Capxon, also
notorious for premature failures. And while I was at it, I replaced a
fourth Capxon capacitor, in the inverter circuit. When I turned it
on, it gave the smae symptoms as the Sceptre monitor. And the
transistors were not shorted.

Researching the Viewsonic, I found it was sold in Germany as a
Belinea, and a complete service manual (including schematic and parts
list) was available for download. What's more, both the Sceptre and
Viewsonic used the same design for the inverter!! Browsing the parts
list, it turns out the transistor in question is a Rohm 2SC4672. DK
is the part identifier, Q indicates the gain range, and K appears to
be some sort of production or date code.

PlainBill

On Tue, 20 Oct 2009 13:01:22 -0700, wrote:

On Fri, 25 Sep 2009 06:59:58 +1000, Franc Zabkar
wrote:

On Thu, 24 Sep 2009 11:32:39 -0700, put finger
to keyboard and composed:

The transistors are in a package equivalent to a Sanyo PCP
http://datasheet.digchip.com/413/413...-0-2SD2099.pdf The
transistors have identification that looks somethng like this:

DK
o_
QH

Sanyo PCP1201:
http://www.semiconductor-sanyo.com/ds_e/ENA1164.pdf
http://pdf.dzsc.net.cn/20090227/200902171141512888.pdf
http://www.semiconductor-sanyo.com/s...6&prod=PCP1201

- Franc Zabkar
Frank,

Well, another problem has raised it's ugly head, and I've finally
firmly established the source of these transistors. The Sanyo part
you tentatively identified was unavailable from my US sources. After
some research, I decided a dxt3150-13 would be an acc3eptable
substitute, so I ordered some. Since the original caps in the monitor
were Elite brand (a known 'bad' manufacturer), I ordered replacements
for them from the same distributor. Before placing the order, I
established the monitor would behave in the expected way with the
shorted transistors removed. I also tested the transformer to ensure
it was not defective.

With the shorted transistors installed, the screen would flash dimly
for a few seconds, then go blank. After they were removed, the screen
would come on for a few seconds, then blank. (This is the normal
result of the protection circuits shutting down the inverter because
of insuffficient output). When the replacements arrived, I soldered
in the new transistors and tested it. It worked perfectly for a few
minutes, so I shut it down and began to replace the questionable caps.

After recapping, the intermittent dim flashes returned!!! However,
neither the original nor the replacement transistors are shorted. It
is a puzzlement; I'll be using a scope to see if I can figure out the
problem.

In the meantime, I had received a Viewsonic VX910 monitor. The owner
indicated it was having difficulty turning on, but would eventually
start. Rather than try to verify this, I simply opened up the
monitor, and found three obviously bad caps. These were Capxon, also
notorious for premature failures. And while I was at it, I replaced a
fourth Capxon capacitor, in the inverter circuit. When I turned it
on, it gave the smae symptoms as the Sceptre monitor. And the
transistors were not shorted.

Researching the Viewsonic, I found it was sold in Germany as a
Belinea, and a complete service manual (including schematic and parts
list) was available for download. What's more, both the Sceptre and
Viewsonic used the same design for the inverter!! Browsing the parts
list, it turns out the transistor in question is a Rohm 2SC4672. DK
is the part identifier, Q indicates the gain range, and K appears to
be some sort of production or date code.

PlainBill
There is a tenedency to say that because two events (no display on two
monitors) occured after a pair of similar events (replacing the caps
on the power supply / inverter boards for the monitors), there must be
a common cause. Well, there was, but it was biological in nature, not
electronic. The scientific term would be 'incompetent technician'.

On the Sceptre monitor, reseating the connections for the CCFLs solved
the problem. It is currently undergoing a 'burn in' phase prior to
being reassembled.

On the Viewsonic monitor, testing the transistors showed that a pair
of them are shorted. And since there were none of the characteristic
probe marks on them, the logical conclusoin is that I INTENDED to test
them, but neglected to.

PlainBill