Sony Trinitron KV-24FS120 four blinks

[YamahaFreak]

This is a customer repair job that has me stumped. Dirty and dusty but otherwise intact KV-24FS120 that won't come out of standby. Pressing POWER gets one relay click, steady flashing LED for about 6-8 seconds, a second relay click, and then a repeating four flashes of the standby LED. The HV never energizes and no other sounds are audible from within. Inspecting the boards revealed no burned, blown, bulged, or otherwise visibly defective components.

I used to know all the standby LED codes...Googling suggests four flashes means something wrong in the power supply, but I haven't been able to get any further. Hopefully this isn't an MCZ chip failure.

[Yamamaya42]

Originally Posted by YamahaFreak

This is a customer repair job that has me stumped. Dirty and dusty but otherwise intact KV-24FS120 that won't come out of standby. Pressing POWER gets one relay click, steady flashing LED for about 6-8 seconds, a second relay click, and then a repeating four flashes of the standby LED. The HV never energizes and no other sounds are audible from within. Inspecting the boards revealed no burned, blown, bulged, or otherwise visibly defective components.

I used to know all the standby LED codes...Googling suggests four flashes means something wrong in the power supply, but I haven't been able to get any further. Hopefully this isn't an MCZ chip failure.

the service info was very easy to find, and free.

https://i.imgur.com/EUVZfUR.jpg

https://www.manualslib.com/manual/68...20.html#manual

[damen]

I remember replacing a zener diode in the power supply in several of those sets.

[YamahaFreak]

Originally Posted by Yamamaya42

the service info was very easy to find, and free.

https://i.imgur.com/EUVZfUR.jpg

https://www.manualslib.com/manual/68...20.html#manual

I'm never quite sure how to respond to replies like this. On the one hand, I'm grateful for the links to helpful info. On the other, it sometimes comes off as condescending, as if I shouldn't have asked at all. In any case, thanks for the input.

[YamahaFreak]

Originally Posted by damen

I remember replacing a zener diode in the power supply in several of those sets.

I'll take a look, thanks!

[zeno]

Blink codes aside usually its over current shut down due to a bad FBT.
Wega sets had LOTS of bad FBT's. If you need to change one
you often need a special tool to get the HV lead out of the FBT.
IIRC the HVSD did not monitor the power supply directly. It watched
for over voltage or over current on the FBT. Most common SD was caused by
cold joints on the vert IC.
Service tip is to monitor the 200V supply to the CRT & see if it pulses.
Also with the DGS unplugged monitor the current draw of the set.
Normal running amps is apx 750 ma. If it pulses above apx 1 amp
its over current SD, FBT or other load on the FBT

BTW the 24" Wega was a hot seller. Perfect size for many. Always ran
out of them in a few weeks & had to wait for the next build to
fill orders.

73 Zeno
LFOD !

[YamahaFreak]

Originally Posted by zeno

Blink codes aside usually its over current shut down due to a bad FBT.
Wega sets had LOTS of bad FBT's. If you need to change one
you often need a special tool to get the HV lead out of the FBT.
IIRC the HVSD did not monitor the power supply directly. It watched
for over voltage or over current on the FBT. Most common SD was caused by
cold joints on the vert IC.
Service tip is to monitor the 200V supply to the CRT & see if it pulses.
Also with the DGS unplugged monitor the current draw of the set.
Normal running amps is apx 750 ma. If it pulses above apx 1 amp
its over current SD, FBT or other load on the FBT

BTW the 24" Wega was a hot seller. Perfect size for many. Always ran
out of them in a few weeks & had to wait for the next build to
fill orders.

73 Zeno
LFOD !

Thanks much for this info. Question: what does DGS stand for? Is this the degauss circuit, or? I'm also probably going to reflow all potentially problematic solder joints just to see if that helps things. As things stand, that relay is the only sign of life, at least audibly. No static charge reaches the CRT face, nothing. Can I even get a replacement FBT for these sets anymore? Interesting to know about these being hot selling sets...must have been a lot of them made.

[zeno]

Yes DGS = Degause.

Reason to unplug is when checking current draw is the DGS is a dead
short when cold & can fool you. A normal set will draw @750 ma running.
Other thing to check is the @130 V. The little PS board has 2 transistors & a @1 ohm fusable. They all can blow from a shorted hoz output or FBT.

73 Zeno
LFOD !