Electronics > Repair

Red Lines on VFD - DVD Player Stopped Working

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paul_g_787:
I have a weird issue here.

I have a HDMI DVD player I have had since 2008. It is a Silvercrest brand player (not sure of model until I pull it out the cabinet) which I got from Lidl in 2008. Up until last night is has been a great player!

I was watching a movie last night and all of a sudden the HDMI signal just dropped. I looked at the players display and it had 'frozen'. The time counter has just stopped but the pause icon was not illuminated.  :-//

I tried turning it off with the remote but it would not respond. So I unplugged it from the mains and left it for 1 minute before connecting it back up.

When it connected back up the display looked like this (see picture). In this state the unit is dead. it will not respond or do anything at all.   :'(

The display is getting very toasty warm in this state so I powered it down right away to avoid further damage.

Now I have done some research and Youtube has taught me that these lines are the Cathode filaments of the Vaccum Fluorescent Display.

Now in normal operation they don't glow red so my instinct says that perhaps this might be a power supply issue?? Maybe bad capacitors?

Has anyone encountered a similar issue before? And if so what might be the cause here.

Gyro:
Yes, that's a severe overvoltage on the VFD filaments. The worry is that the other supply rails from the PSU have gone up by a similar amount, which would almost certainly be fatal to the ICs.

I don't think such a fault would be down to a capacitor problem, they tend to be more subtly, causing unreliable operation, at least initially. This looks like a sudden loss of PSU regulation, maybe a semiconductor failure in the feedback loop.

It's hard to say more without knowing what has happened to the other supply rails. The player is clearly well out of warranty, but I don't know how confident / competent you feel about working on mains powered equipment.

paul_g_787:

--- Quote from: Gyro on November 24, 2021, 07:13:28 pm ---Yes, that's a severe overvoltage on the VFD filaments. The worry is that the other supply rails from the PSU have gone up by a similar amount, which would almost certainly be fatal to the ICs.

I don't think such a fault would be down to a capacitor problem, they tend to be more subtly, causing unreliable operation, at least initially. This looks like a sudden loss of PSU regulation, maybe a semiconductor failure in the feedback loop.

It's hard to say more without knowing what has happened to the other supply rails. The player is clearly well out of warranty, but I don't know how confident / competent you feel about working on mains powered equipment.

--- End quote ---


I am hoping it has not fried the ICs  :(

Looks like I will be pulling the player out. I will take some photos of the inside.

I guess a good first step is to see if the power supply can be disconnected and I will test the voltages of the outputs rails.


Yes I am more than confident/competent at working on mains powered equipment and well aware of the potential dangers.

Gyro:
That looks like a good first step (isolate and measure) then. Best case would be a fault just on the VFD filament supply, but the fact that all other functionality ceased at the same time seems a bad omen.

paul_g_787:

--- Quote from: Gyro on November 24, 2021, 07:27:02 pm ---That looks like a good first step (isolate and measure) then. Best case would be a fault just on the VFD filament supply, but the fact that all other functionality ceased at the same time seems a bad omen.

--- End quote ---

I know :(

I really hope it is something simple. Would be a shame as this player is great.

Will post back in the next few days with my findings and photos.

There was no magic smoke or anything with a funky smell. But even so could be serious.

I am assuming that the VFD filaments would run on a high negative DC voltage?

I have never really worked with VFDs before. To me it seems like the work just like a valve.

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