Sony watchman FDL-330S Screen going black issue

[yekwart]

Hi, I’m hoping for a bit of technical help here.

I have a Sony watchman FDL-330S portable TV. https://www.youtube.com/watch?v=nUjJN-Vpkz8 Not my youtube video but same model TV.

It has an issue where when I turn it on it works for only about 30 seconds then the screen goes black but the sound will still be running. If I turn it off, then on again several seconds later, it will work for maybe another 5-10 seconds then go black again. It does this if I am playing a video using the 3.5mm a/v input jack or when I’m just tuned into static, on the analog bands.

I figure this must be a capacitor issue as the device is 30 years old and they have never been changed. But, I thought I should just check here to see if it may be something else. I did open it open and check the capacitors, no obvious damage could be seen, though there were a few capacitors I couldn’t see clearly.

Thanks,

[Electronic M]

How fresh are your batteries and have you tried powering it off an AC adapter. Portable TVs especially the image circuits are power thirsty and won't work if battery voltage slumps enough under load. Audio and received stages can work at lower voltage than the image circuits.

[yekwart]

Thanks for the help.

The batteries were not new. I checked them with a multimeter and they are all reading roughly 1.3v. Unfortunately, I don't have 4 new ones. I did replace them with some other ones that showed 1.41v when tested and when I swithced the TV on it lasted for 4 minutes before going black. When switched back on it lasted 20 seconds before going black.

I haven't tested using an AC adapter yet, but when I find a matching one I will.

Edit: Just noticed in the manual it says "As the batteries become weak, the sound becomes distored and the picture becomes dim. When the picture becomes dim, replace all the batterries with new ones."

The sound didn't sound distored to me and the screen going frrom working to black, was pretty instant.

Edit2: Troubleshooting section in manual says "No Picture but good sound - Batteries are weak"

So still very possible

[yekwart]

I bought new batteries today and that seems to have solved the problem. I'm pretty shocked that when the batteries dip below 1.35-1.4v it is considered low power by the TV. Running these things in their day off batteries would have cost a fortune. Manual says they would last 2.5 hours, I'd be surprised if it made it that long.

Anyway, problem solved and I appreciate the input. Just need to get a power supply for it now.

[Electronic M]

Happy to help.

[maxhifi]

Originally Posted by yekwart

I bought new batteries today and that seems to have solved the problem. I'm pretty shocked that when the batteries dip below 1.35-1.4v it is considered low power by the TV. Running these things in their day off batteries would have cost a fortune. Manual says they would last 2.5 hours, I'd be surprised if it made it that long.

Anyway, problem solved and I appreciate the input. Just need to get a power supply for it now.

Yep and that's when batteries didn't come in huge bulk backs from Costco yet, so you had to pay actual money for a pack of four! AA batteries were the life blood of modern devices in the 80s though.

[rcpilot23]

Just wondering if you have a service manual for your FDL-330S?
Mine turns on with batteries or 6V DC adapter but the display is white.

thanks

[rcpilot23]

This issue has been resolved with another lcd and inverter board from a donor unit.