Power supply problem on Orion DVCR2002 VCR/DVD combo

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The unit doesn't have power. I found two diodes (in parallel) on the
power supply board seem got burnt (burn mark on the PCB). Took the
diodes off the board, one is dead (zero resistance). The other one
seems to work. I replaced the dead one with a light emitting diode
(that's the one have handy, ok ). Plug the unit in and it has power
to show display on panel and disc tray works. I put a disc in and
closed the tray, after spinning for a few seconds, the other diods (not
the one I put in) over heat and burnt (smoke). The PCB close to the
diodes is a kind of separated from the board, looks like from
overheating.

One other thing. The largest capacitor has some whitish stuff sticks
to it (it is dry though). I wonder if it came from the capacitor, or
it was put there on purpose. The cap of the capacitor looks flat and
good.

I don't have much electronics repair experiences and hope to get some
guidance here. What should I look for? How to test if the capacitor
is good or bad (I only have a multimeter).

Thanks a lot in advance!

 

[Jumpster Jiver]

The unit doesn't have power. I found two diodes (in parallel) on the
power supply board seem got burnt (burn mark on the PCB). Took the
diodes off the board, one is dead (zero resistance). The other one
seems to work. I replaced the dead one with a light emitting diode
(that's the one have handy, ok ). Plug the unit in and it has power
to show display on panel and disc tray works. I put a disc in and
closed the tray, after spinning for a few seconds, the other diods (not
the one I put in) over heat and burnt (smoke). The PCB close to the
diodes is a kind of separated from the board, looks like from
overheating.

One other thing. The largest capacitor has some whitish stuff sticks
to it (it is dry though). I wonder if it came from the capacitor, or
it was put there on purpose. The cap of the capacitor looks flat and
good.

I don't have much electronics repair experiences and hope to get some
guidance here. What should I look for? How to test if the capacitor
is good or bad (I only have a multimeter).

Thanks a lot in advance!

The white stuff on thte cap is probably glue.
You need to test all of the components in the power supply, and replace
them with equivalent parts, not just what you have handy.
You will need an ESR meter to test the capacitors.
Once you replace all the bad components in the power supply, the unit
should power on again, but if you miss just one bad part, it could cause
a cascade failure of many parts, including any you may have changed.

 

[Mark D. Zacharias]

after spinning for a few seconds, the other diods (not
the one I put in) over heat and burnt (smoke).

Diode OK til motor spins, probably a bad spindle motor (shorted). Pretty
common problem.


Mark Z.

 

[blueking]

Do your professionals test all components ? I was hoping this is an
easier fix. Do you have a more specific suggestion?

Thanks.

 

[blueking]

The motor did spin. Will that still be a spin motor problem? One fact
is that the diodes got hot even when the motor doesn't spin. Any other
suggestions? Thanks a lot.

 

[Mr. Land]

Are you really saying that you replaced a power supply diode with an
LED?!?

....that's amazing.

 

[blueking]

Why is it so amazing? Isn't the LED a diode that emits light? It only
took a genius like me to figure that out .

Seriously, it worked, well briefly. But it looks like the overheat of
the diodes were caused by some other problems because the LED is also
pretty hot (without motor spinning).

Please keep suggestions coming in. I hope this is not too complicated
problem.

Thanks again to all the pros!

 

[Mark D. Zacharias]

What often happens is that the motor is shorted through 1/2 it's rotation.
This means the motor spins weakly, and draws LOTS of current. If the motor
happens to be stopped on the shorted phase, and if it's really
short-shorted, meaning 0 ohms instead of 1 or 2 ohms maybe, then the motor
won't go until you "help' it along.

Mark Z.

 

[blueking]

Thanks Mark.

I tried to unplug the power to the disc loader. The LED still got hot.
So, I think there is something else that's not working right. How
should I take the next step?

By the way, if something is short, shouldn't the fuse break instead of
the diodes? The fuse is fine.

Thanks again.

 

[Mr. Land]

It's amazing because a power supply diode is usually designed to handle
a lot of current (like 2, 3 or more amps), while an LED is usually
designed in just the opposite way, that is, to operate with a minimal
amount of current passing through it. (like 10 mA). You stated that
there was heat discoloration on the PCB near the diodes - that
indicates that they ran hot, which usually means they carry a lot of
current during the normal operation of the circuit (are are likely
designed that way).

The fact, then, that you were able to replace one of these devices with
an LED, apply power, and not have the LED instantly explode
is...well...amazing.