Zenith DVD player -- power light stays on, nothing works.

[spamtr...@gmail.com]

This Zenith DVD2381 has worked for years, except for a spell a few
years ago when the tray would shudder but not quite open and close.
I managed to free it up.

So tonight, when there was nothing on TV, my wife told me that when
she had tried to play a DVD on Tuesday, it didn't work. She tried
to turn it off, but the light in the power button stayed on. Nothing
appears on the display: no "Hello," no "No disc," no nothing.

We tried unplugging it and plugging it in again, but that did not
help.

The thing still looks pristine inside, so I hate to junk it without
giving repair a shot.

Does this sound like a simple problem to fix?

How do laser safety interlocks work on those old DVD players? If
the lid were off, would that stop all functionality? My SWAG is
that this is not working.

Many thanks in advance for any suggestions.

Mike

[N_Cook]

try googling model number and "badcaps"

[spamtr...@gmail.com]

On Friday, February 6, 2015 at 3:59:18 AM UTC-8, N_Cook wrote:
> On 06/02/2015 09:37, spamtr...@gmail.com wrote:

> > This Zenith DVD2381 has worked for years, except for a spell a few
> > years ago when the tray would shudder but not quite open and close.
> > I managed to free it up.
> >

...

> try googling model number and "badcaps"

Thanks for your response!

Nothing leapt out at me. The electrolytics in and around the power supply
also look pristine. They are marked "KME" and "SMS", so likely Chemi-Con.

Do Chemi-Con electrolytics have a bad reputation? They are not called
out as bad on the badcaps site.

[Michael Black]

On Fri, 6 Feb 2015, spamtr...@gmail.com wrote:

> On Friday, February 6, 2015 at 3:59:18 AM UTC-8, N_Cook wrote:
>> On 06/02/2015 09:37, spamtr...@gmail.com wrote:
>
>>> This Zenith DVD2381 has worked for years, except for a spell a few
>>> years ago when the tray would shudder but not quite open and close.
>>> I managed to free it up.
>>>
> ...
>> try googling model number and "badcaps"
>
> Thanks for your response!
>
> Nothing leapt out at me. The electrolytics in and around the power supply
> also look pristine. They are marked "KME" and "SMS", so likely Chemi-Con.
>

But looks can be deceiving.

That Acer LCD monitor I brought home sort of worked, except it kept
resetting to the point where it was showing the logo on the screen. So
the power supply was nominally good. I changed the larger value
electrolytics in the power supply, none of them looked bad. And it's
worked fine since.

> Do Chemi-Con electrolytics have a bad reputation? They are not called
> out as bad on the badcaps site.
>
>

A little bit of information is worse than a lot.

There were instances of "bad caps" but electrolytics by nature can dry
out. It's about how they are used, and the heat they see.

In the tube days, most equipment had only a handful of electrolytics, in
the power supply and to bypass the cathode resistor(s) in the audio
amplifier chain. You could usually easily tell there was a bad
electrolytic, you'd hear hum in the speaker (because the power supply
filter capacitor went bad), or maybe lesser audio output.

Transistorized gear brought a lot more electrolytics, since tubes were
high voltage low current, and transistors were love voltage high current.
They needed electrolytics because the lower impedances meant a need for
larger valuce capacitors, and the only way to get that in a small package
was electrolytic capacitors.

And take transisfor radios from 40 or 50 years ago, and the electrolytics
generally need replacing because they are now old.

But the real change was when switching supplies came along. Power supply
capacitors before that only had to keep out 60 or 120Hz, pretty low
frequencies. Switching supplies got by with lower value electrolytics,
since they operated at a higher frequency, tens of KHz, but that meant the
electrolytics had to work harder. And that's why they are now suspect
when something with a switching supply goes bad. They are more likely to
go bad than a diode or other component.

Michael

[N_Cook]

In the old days you would never see 120 deg C rated caps, even with all
those glowing valves the caps did not get that hot. Combined with
smaller physical size for the same rating. Has QC of elecrolyte and
materials really got that good to allow for half size caps , compared to
sizws before?

[Dave Platt]

>This Zenith DVD2381 has worked for years, except for a spell a few
>years ago when the tray would shudder but not quite open and close.
>I managed to free it up.
>
>So tonight, when there was nothing on TV, my wife told me that when
>she had tried to play a DVD on Tuesday, it didn't work. She tried
>to turn it off, but the light in the power button stayed on. Nothing
>appears on the display: no "Hello," no "No disc," no nothing.
>
>We tried unplugging it and plugging it in again, but that did not
>help.
>
>The thing still looks pristine inside, so I hate to junk it without
>giving repair a shot.
>
>Does this sound like a simple problem to fix?

One not-uncommon failure mode in such devices, is bad electrolytic
capacitors. They may go "high ESR" and fail to filter the power
supply voltages properly, or they may swell and leak (failing to
filter, and possibly damaging the PC board traces).

A decent capacitor ESR tester (which is different than a capacitance
meter) can often identify such caps.

"Re-capping" the device requires identifying the failed caps (or just
identifying "all the usual suspects"), removing, and replacing. If PC
board traces have been damaged by electrolyte leakage, it would be
necessary to rebuild them or bridge over the damaged areas.

It's definitely possible to do. It often isn't done commercially for
lower-value products due to the cost of labor. When you can buy a DVD
player for under $100, spending an hour of technician labor at $100
isn't a great bargain.