Sony HB-F1XDJ screen noise / keeps resetting itself

Supporter (3)

22-01-2021, 22:54

Hello, I've had an HB-F1XDJ for about three years. About a year ago I started getting issues with the video signal, where I would periodically get "noise" or the image would roll and then go back to normal. I actually thought it was a problem with my CRT for a while until I realized it happens on other ones too. It would only happen after the system was on for a while.

Anyway, a few months later it got worse and the system is now in such dire state that it can barely even boot up. In fact, it will now spontaneously reboot itself very soon after turning it on. When this happens the power LED dims, and the system only comes back up once the LED brightens again. The period between shutdowns gets shorter the longer it is on. I have posted a video here:

https://www.youtube.com/watch?v=7OhX9CCxXzA

I'm just getting around to trying to fix it, but have come up blank. The LED behavior and fact that there is a "cooldown" suggests some kind of power delivery issue. I was thinking caps, so I fully recapped the system (I should note the HIC-1 was already recapped when I got it, when the system worked fine) with no change in results. The caps that I replaced did not have any evidence of failure or leakage, board was clean. I will admit there is one cap I did not replace-- the extremely big cap near the cartridge slot (forget the specific value, 10000uf?) since it's glued or epoxied down and I wasn't sure I could remove it without damaging things. Anyone know if that big cap is part of the power circuitry? Visually it is not bulging, but I know that isn't a good indicator of capacitor health.

In general, what might be wrong with this machine? Do I need to build a new power supply somehow? Does anyone have some tips on isolating what exactly is wrong with it? Not exactly in the mood to have to go hunting for a new system, I've been totally happy with this little guy. Your help is appreciated!

By Daemos

Paragon (1794)

23-01-2021, 00:11

Definetly a power issue. Do you have a scope to check how it behaves?

Check for shorts as well. Power led dimming and then a system reboot may indicate a short circuit.

By Mr Ksoft

Supporter (3)

23-01-2021, 03:20

Unfortunately, I do not have a scope, only a multimeter. I have been hesitant to use it to check the voltages on the power supply connector (to see if the issue is the supply itself, or something further down the line) because there is no indication as to which pin is which and I don't want to accidentally connect two voltage lines together. I tried finding documentation online but failed.

By Daemos

Paragon (1794)

23-01-2021, 19:35

There has to be ground somewhere on the chassis. Use your multimeter to find it. You simply connect to - on a cap and search for metal parts connected to it amd you will have ground. Then you can safely start looking for 5 volts

By Mr Ksoft

Supporter (3)

24-01-2021, 01:17

Thanks, my electrical experience is still quite weak. For some reason I could not get any voltage reading out of the PSU>motherboard connection. No matter what ground point I used all the pins read 0-0.03V. Which of course can't be right cause the system is booting up.

I did, however, get a reading off the voltage regulator next to the connector. It's only getting about 6.94V on the "input" and 4.6V on the output. I think it is supposed to be 12V->5V. I'd say that suggests a power delivery issue, probably before the regulator if it's not getting 12V...