Need to find components in digital cable box power supply circuit

[Rob Beattie]

Hello everyone,
I have got a digital cable box manufactured by Pace. It died the other
night and does not power up anymore. After opening it up I checked the
fuse and found that it was still intact so I have decided on starting
to replace components in the power supply circuit with the hope that
eventually find the faulty one.
There are a couple of components that I can't find stocked anywhere so
I am hoping that someone here could suggest alternatives or suppliers.
Here is the info for the parts:-

1. A transister(I think) To-92 package with the numbers/letters
'ts 4 31AI' printed on it and is manufactured by ST Electronics.

2. A transformer from Orega(They don't appear to have a website) which
has quite a few numbers printed on it.
40328-86
237-5303040
10615620

I think the top one is the part number.

I would appreciate any help provided.

Thanks.

 

[CJT]

Hello everyone,
I have got a digital cable box manufactured by Pace. It died the other
night and does not power up anymore. After opening it up I checked the
fuse and found that it was still intact so I have decided on starting
to replace components in the power supply circuit with the hope that
eventually find the faulty one.

!

That's a bit of a sledgehammer approach, don't you think?

 

[colin]

!

That's a bit of a sledgehammer approach, don't you think?

Its quite a comon aproach for some types of problem, although in power suply
circuits it can be less than satisfactory as one component might take out
several others, and you have to replace all the fualty ones at once or theyl
al fail again.

Also it might be cheaper to replace the unit altogether if u have to replace
too many lol, depends how good you are at identifing the sort of components
that are most likely to fail.


its best to at least use a multimeter to check resistances etc first, and
then check for any voltages (but be safe)

try measure it with a multimeter.

If the transformer has blown it will smell realy bad and look burnt and
probably take out the fuse, unles its failed open circuit wich would be
unusual, althogh they sometimes have a temperature protection device wich
might fail.

 

[James Sweet]

Hello everyone,
I have got a digital cable box manufactured by Pace. It died the other
night and does not power up anymore. After opening it up I checked the
fuse and found that it was still intact so I have decided on starting
to replace components in the power supply circuit with the hope that
eventually find the faulty one.
There are a couple of components that I can't find stocked anywhere so
I am hoping that someone here could suggest alternatives or suppliers.
Here is the info for the parts:-

Randomly replacing components is a ridiculous way of trying to repair
something, have you bothered to do any testing at all? Measured any
voltages? How do you even know the power supply is the problem? It could be
that the microcontroller isn't telling it to turn on. At the very least you
could start with likely parts and not just try to replace everything. Sounds
like you're more likely to turn the cable box into scrap than repair it.

 

[Rob Beattie]

Randomly replacing components is a ridiculous way of trying to repair
something, have you bothered to do any testing at all? Measured any
voltages? How do you even know the power supply is the problem? It could be
that the microcontroller isn't telling it to turn on. At the very least you
could start with likely parts and not just try to replace everything. Sounds
like you're more likely to turn the cable box into scrap than repair it.

I can see what you and the other respondents are advising but I don't
know enough about electronics to be able to do more than checking
fuses, resistors and perhaps voltages(although I don't know what the
voltages should be so perhaps I can't do even that). You don't know of
any sites which could help me to learn(not just basic components but
also testing power supplies themselves)?
The reason I am willing to swap everything in sight is that I am very
good at soldering & desoldering and can easily do so for any
electronic parts on the pcb whether they are through hole or surface
mount.
Having said that I must concede your point that if I knew how to test
diodes, transistors and capacitors etc while still placed on board it
would help a great deal.
I am interested in your microcontroller suggestion. How does it fit in
to the start up routine?
Also I should have mentioned that when I apply power I hear a faint
clicking noise coming from somewhere aroung the power supply circuit.
Does that clue give anyone an idea?

 

[Franc Zabkar]

Hello everyone,
I have got a digital cable box manufactured by Pace. It died the other
night and does not power up anymore. After opening it up I checked the
fuse and found that it was still intact so I have decided on starting
to replace components in the power supply circuit with the hope that
eventually find the faulty one.

Why don't you reverse engineer the circuit and get an idea of how it
works? At the very least get the datasheets for the various
components, in particular the PWM controller IC - the datasheets may
include sample application circuits.

Have you even measured the PSU's output voltage(s)?

There are a couple of components that I can't find stocked anywhere so
I am hoping that someone here could suggest alternatives or suppliers.
Here is the info for the parts:-

1. A transister(I think) To-92 package with the numbers/letters
'ts 4 31AI' printed on it and is manufactured by ST Electronics.

That's a 1.25V voltage reference:
http://www.st.com/stonline/books/pdf/docs/5558.pdf

It's probably equivalent to a garden variety TL431.

2. A transformer from Orega(They don't appear to have a website) which
has quite a few numbers printed on it.
40328-86
237-5303040
10615620

Transformers in switchmode PSUs rarely fail.

I think the top one is the part number.

I would appreciate any help provided.

Thanks.

- Franc Zabkar

 

[James Sweet]

I can see what you and the other respondents are advising but I don't
know enough about electronics to be able to do more than checking
fuses, resistors and perhaps voltages(although I don't know what the
voltages should be so perhaps I can't do even that). You don't know of
any sites which could help me to learn(not just basic components but
also testing power supplies themselves)?
The reason I am willing to swap everything in sight is that I am very
good at soldering & desoldering and can easily do so for any
electronic parts on the pcb whether they are through hole or surface
mount.
Having said that I must concede your point that if I knew how to test
diodes, transistors and capacitors etc while still placed on board it
would help a great deal.
I am interested in your microcontroller suggestion. How does it fit in
to the start up routine?
Also I should have mentioned that when I apply power I hear a faint
clicking noise coming from somewhere aroung the power supply circuit.
Does that clue give anyone an idea?

It means something is shorted on the output side generally and causing the
supply to shut down. I would politely suggest that you read up on this stuff
and learn how to test these components, it's not particularly difficult and
doesn't require any expensive tools. You'll run into problems with things
frequently and if you haphazzardly replace everything you'll replace a lot
of perfectly good parts and learn nothing in the process.