DVD/ STEREO SYSTEM: bridge rectifier question

[b]

I've just 'fixed' a dvd/amp/stereo all in one made by the world famous
Sunstech
( model hf-dv55m ; manual and details here
http://www.sunsiberica.com/productos.php?listar_producto=5)

Unit was dead, on power up some garbled text appeared in the display.
measuring o/p voltages on the psu pcb, I saw the display lines were ok
but the 5v line was dead. Probing further, I found an o/c cct
protector or fusible resistor (marked '3000') in the DC output of one
of the bridge rectifiers.

I eventually traced the cause to a partially shorted spindle motor.
Changed that and the beast works, but I am concerned that the bridge
rectifier (marked GW RS202; appearance-wise, its like number 2 in
this pic http://arcadecontrols.com/BBBB/bridges.jpg ) gets extremely
hot in operation (you can't keep a finger on it at all). Not sure if
that is normal; the pcb looks slightly scorched near there, so could
have always been this way for all I know. The other identical bridge
is pretty much cool in use.

So, question is, is this likely to be leaky? I've only ever had one
case of a similar leaky rectifier, in a VCR a few years ago. In my
experience they normally just short out. Maybe fit a beefier one?

Any thoughts welcome.
-B

 

[Jamie]

b wrote:

I've just 'fixed' a dvd/amp/stereo all in one made by the world famous
Sunstech
( model hf-dv55m ; manual and details here
http://www.sunsiberica.com/productos.php?listar_producto=5)

Unit was dead, on power up some garbled text appeared in the display.
measuring o/p voltages on the psu pcb, I saw the display lines were ok
but the 5v line was dead. Probing further, I found an o/c cct
protector or fusible resistor (marked '3000') in the DC output of one
of the bridge rectifiers.

I eventually traced the cause to a partially shorted spindle motor.
Changed that and the beast works, but I am concerned that the bridge
rectifier (marked GW RS202; appearance-wise, its like number 2 in
this pic http://arcadecontrols.com/BBBB/bridges.jpg ) gets extremely
hot in operation (you can't keep a finger on it at all). Not sure if
that is normal; the pcb looks slightly scorched near there, so could
have always been this way for all I know. The other identical bridge
is pretty much cool in use.

So, question is, is this likely to be leaky? I've only ever had one
case of a similar leaky rectifier, in a VCR a few years ago. In my
experience they normally just short out. Maybe fit a beefier one?

Any thoughts welcome.
-B
you should check the bridge, you could have one diode in there that is

leaking and check the filter cap that is attached to that with a
voltage supply that has a amp meter on it, out of circuit.

 

[Franc Zabkar]

On Sun, 13 Dec 2009 17:55:45 -0800 (PST), b
<reverend_rogers@yahoo.com> put finger to keyboard and composed:

I eventually traced the cause to a partially shorted spindle motor.
Changed that and the beast works, but I am concerned that the bridge
rectifier (marked GW RS202; appearance-wise, its like number 2 in
this pic http://arcadecontrols.com/BBBB/bridges.jpg ) gets extremely
hot in operation (you can't keep a finger on it at all). Not sure if
that is normal; the pcb looks slightly scorched near there, so could
have always been this way for all I know. The other identical bridge
is pretty much cool in use.

So, question is, is this likely to be leaky? I've only ever had one
case of a similar leaky rectifier, in a VCR a few years ago. In my
experience they normally just short out. Maybe fit a beefier one?

I've seen several instances of leaky rectifiers in linear supplies.
The ripple on the output was very obvious in my case, though.

An RS202 crosses to an NTE166 (100V, 2A):
http://www.nteinc.com/specs/100to199/pdf/nte166.pdf

Here are other datasheets:
http://www.datasheetarchive.com/search.php?t=0&q=rs202&manystr=&sub.x=24&sub.y=12

You may want to measure the current drawn by the load.

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

 

[b]

thanks franc and jamie.
I changed the rectifier for a 2KBP02 (2A) I had lying around. Still
got hot. Connecting an ammeter in series with the load gave a pretty
negligible reading in tuner mode, but an average reading of 1.3A, with
occasional peaks of 1.8 or so, when the dvd was in use.
Since at no time the reading exceeded the 2A rating of the rectifier,
I'm assuming this is just a case of penny pinching in the design, with
the component working very close to the limit. I'll keep it in use a
while and see, and based on that, may upgrade the rectifier to offset
future probs.
-B