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From: Alexis.happyphoenix on 23 Jul 2010 14:51
I have perhaps foolishly tackled the repair of my freeview box -
Tvonics MDR-250 - for which no service information appears to be
available. I'm an amateur, btw. (Fault is it's powering on and
immediately shutting down repeatedly.)

I have a suspect component, marked Q700 on the PCB, suggesting that
it's a transistor of some sort, and marked 654Z. I've tried googling
for this part number but can't find any information.

Its a 6 legged device, and I don't know of any 6 legged types of
transistor. The only alternative device I've come up with is an opto-
isolator - though I don't know what the standard PCB identifier would
be for one of these.

2 pairs of pins are connected together, so there are effectively 4
legs. It's in a very cramped part of the board (next to the power
socket and what I think is a fuse on it's own little sub-board) so I
can't really work anything out from what it's connected to.

Anyways, I need some info because it's either completely short
circuit, or it's connected to something which is completely short
circuit, and I can't do much unless I find out what the thing is.

Any suggestions welcome
TIA
Alexis
From: Randy Day on 23 Jul 2010 21:51
In article <a03347a2-53d7-46a2-8785-
1aea816d9c3b(a)y11g2000yqm.googlegroups.com>,
alexis.happyphoenix(a)gmail.com says...
> I have perhaps foolishly tackled the repair of my freeview box -
> Tvonics MDR-250 - for which no service information appears to be
> available. I'm an amateur, btw. (Fault is it's powering on and
> immediately shutting down repeatedly.)
>
> I have a suspect component, marked Q700 on the PCB, suggesting that
> it's a transistor of some sort, and marked 654Z. I've tried googling
> for this part number but can't find any information.
>
> Its a 6 legged device, and I don't know of any 6 legged types of
> transistor. The only alternative device I've come up with is an opto-
> isolator - though I don't know what the standard PCB identifier would
> be for one of these.
>
> 2 pairs of pins are connected together, so there are effectively 4
> legs. It's in a very cramped part of the board (next to the power
> socket and what I think is a fuse on it's own little sub-board) so I
> can't really work anything out from what it's connected to.
>
> Anyways, I need some info because it's either completely short
> circuit, or it's connected to something which is completely short
> circuit, and I can't do much unless I find out what the thing is.

It's probably dual transistors in a
SOT pack. Searching Digikey will
likely pull up dozens of
contenders.

They can be dual npn, dual pnp or one
of each. Dual MOSFETs also use the
package. With two legs connected,
they could be wired common-emitter
for switching, push-pull for
amplification (though not likely), or
just about any combination of two
transistors.

Unfortunately, it could also be a
small IC like a single logic gate.
Lots of stuff uses the SOT package
nowadays.

Wish I could be more help.

--- news://freenews.netfront.net/ - complaints: news(a)netfront.net ---
From: Alexis.happyphoenix on 27 Jul 2010 05:30
On 24 July, 01:51, Randy Day <randy....(a)sasktel.netx> wrote:
> In article <a03347a2-53d7-46a2-8785-
> 1aea816d9...(a)y11g2000yqm.googlegroups.com>,
> alexis.happyphoe...(a)gmail.com says...
>
>
>
> > I have perhaps foolishly tackled the repair of my freeview box -
> > Tvonics MDR-250 - for which no service information appears to be
> > available.  I'm an amateur, btw. (Fault is it's powering on and
> > immediately shutting down repeatedly.)
>
> > I have a suspect component, marked Q700 on the PCB, suggesting that
> > it's a transistor of some sort, and marked 654Z.  I've tried googling
> > for this part number but can't find any information.
>
> > Its a 6 legged device, and I don't know of any 6 legged types of
> > transistor.  The only alternative device I've come up with is an opto-
> > isolator - though I don't know what the standard PCB identifier would
> > be for one of these.
>
> > 2 pairs of pins are connected together, so there are effectively 4
> > legs.  It's in a very cramped part of the board (next to the power
> > socket and what I think is a fuse on it's own little sub-board) so I
> > can't really work anything out from what it's connected to.
>
> > Anyways, I need some info because it's either completely short
> > circuit, or it's connected to something which is completely short
> > circuit, and I can't do much unless I find out what the thing is.
>
> It's probably dual transistors in a
> SOT pack. Searching Digikey will
> likely pull up dozens of
> contenders.
>
> They can be dual npn, dual pnp or one
> of each. Dual MOSFETs also use the
> package. With two legs connected,
> they could be wired common-emitter
> for switching, push-pull for
> amplification (though not likely), or
> just about any combination of two
> transistors.
>
> Unfortunately, it could also be a
> small IC like a single logic gate.
> Lots of stuff uses the SOT package
> nowadays.
>
> Wish I could be more help.
>
> --- news://freenews.netfront.net/ - complaints: n...(a)netfront.net ---

Ok that's a hundred percent more info than I had and makes a lot of
sense. I am duly grateful :-)

Many thanks
Alexis
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