Sony GDM-FW900: Help me diagnose why it won't turn on? (Video included)

[jrodefeld]

Hi everyone,

I have a vintage Sony GDM-FW900 crt monitor that I really enjoy using, but it has developed a problem and won't start up.

This unit was completely serviced a few years ago by Unkle Vito in Los Angeles and it fully passed all tests, was factory calibrated, etc. There was a faulty part (can't remember exactly which one) that was replaced at another repair shop about a year ago. Other than that, it's been working great.

I just say all that to say that this unit is probably in pretty good shape since it's been fully serviced and checked recently.

I'm in a location that doesn't really have any businesses that repair CRTs (that I could find) so I'm wondering if it's something I could potentially do myself?

I suspect something relatively simple.

What happens is that when I push the power button, the unit makes four screeching / clicking sounds, then goes into standby. Nothing shows up on the screen.

There's also a place on one of the boards where there is a flashing blue light that lights up along with the screeching sound.

Here's a video I recorded of the behavior:

https://new-content.wistia.com/medias/36c9b89iww

Any clue what the problem is?

[Topcat]

Re: Sony GDM-FW900: Help me diagnose why it won't turn on? (Video included)

Shorted CRT is my guess. These were known for bad tubes.

[momaka]

Re: Sony GDM-FW900: Help me diagnose why it won't turn on? (Video included)

There's also a place on one of the boards where there is a flashing blue light that lights up along with the screeching sound.

Here's a video I recorded of the behavior:

https://new-content.wistia.com/medias/36c9b89iww

Any clue what the problem is?

Looks like spark gap SG901 is firing off, same as on one of my faulty GDM-FW900 monitors.
The problem on mine ended up being the tube going bad / leaked air. Not repairable, unfortunately. The thread can be found here:
https://www.badcaps.net/forum/showthread.php?t=15248

And the exact issue described here:
https://www.badcaps.net/forum/showpo...3&postcount=22

I also already tried changing the flyback transformer on mine and even swapping parts from my other working GDM-FW900.

So unfortunately, yours is probably dead / unrepairable too.

That being said, DON'T TOSS IT!
Try selling it for parts on eBay or elsewhere. The parts from this monitor can be used to revive other Sony CRTs, so it's not a total loss. Granted it might take a while (a year or more) before you find a buyer for the parts, but it's worth it, IMO. Finding used parts for CRTs is becoming harder and harder nowadays.

[3dfan]

Re: Sony GDM-FW900: Help me diagnose why it won't turn on? (Video included)

Hi everyone,

I have a vintage Sony GDM-FW900 crt monitor that I really enjoy using, but it has developed a problem and won't start up.

This unit was completely serviced a few years ago by Unkle Vito in Los Angeles and it fully passed all tests, was factory calibrated, etc. There was a faulty part (can't remember exactly which one) that was replaced at another repair shop about a year ago. Other than that, it's been working great.

I just say all that to say that this unit is probably in pretty good shape since it's been fully serviced and checked recently.

I'm in a location that doesn't really have any businesses that repair CRTs (that I could find) so I'm wondering if it's something I could potentially do myself?

I suspect something relatively simple.

What happens is that when I push the power button, the unit makes four screeching / clicking sounds, then goes into standby. Nothing shows up on the screen.

There's also a place on one of the boards where there is a flashing blue light that lights up along with the screeching sound.

Here's a video I recorded of the behavior:

https://new-content.wistia.com/medias/36c9b89iww

Any clue what the problem is?

hi, just wondering if you were able to fix that issue?

[momaka]

Re: Sony GDM-FW900: Help me diagnose why it won't turn on? (Video included)

hi, just wondering if you were able to fix that issue?

I doubt it.
This is usually the sign of a CRT tube that has lost vacuum / leaked in air.

Not repairable, unless you have or know someone that has a large glass furnace and extremely high pressure vacuum pump to re-seal the tube... and even then, I don't think it's something anyone could do "at home", even with these type of tools.

[stj]

Re: Sony GDM-FW900: Help me diagnose why it won't turn on? (Video included)

maybe, but i have had crt sockets with shorts between the contacts and spark ring before
those widescreen tubes usually fail with a shorted blue gun causing a blue field in the background

[momaka]

Re: Sony GDM-FW900: Help me diagnose why it won't turn on? (Video included)

Interesting.
But most of the failures I've seen mentioned here and on Youtube were usually with that dreaded screeching noise and SG901 firing off.

The only way I can get SG901 not to fire off on mine is to disconnect the HV anode from the tube. Then the monitor will attempt to turn On for a few seconds... well, at least before the HV on the anode goes too high and jumps to ground somewhere. I haven't made a proper HV load for it yet, though I've purchased the parts not too long ago (it's also for a DIY HV probe with a cubic ton of 1M resistors.)

Easiest way to see if the tube has gone to air is to put 5V between H1 and H2 (tube heater) pins on the tube with the A-board / tube socket disconnected. If you don't get faint orange glow from the heater, tube has certainly lost vacuum. Mine's that way.

[stj]

Re: Sony GDM-FW900: Help me diagnose why it won't turn on? (Video included)

if the tube loses vac you will see a mottled effect on the face as the phosphor starts to fall off the glass.