Windy II Toshiba chassis PB7534-1 No Primary HV Output

[GeekMan1222]

Any idea why a windy 2 toshiba chassis's primary HV output isnt running???

One of our machines chassis was running fine but it stopped working on a return. Finally took time to look at it today in more detail.
Chassis would not energize and would just sit there chirping from one of the transformers.

Things done:
Found bad solders on the HV control IC daughter board, reflowed that.
Found the HOT and the FBT FET were both fully shorted. I replaced them both
Briefly poked around tested around for bad diodes or other things. However couldn't find anything out of the blue.

Other observations:
This chassis was clearly recapped partially at some point in Japan and has a service asset tag from the repair house in Japan.
There was water exposure to the chassis at one point. Some resistors have rust/corrosion on them.
The tube grounding strap for the dag has one snapped spring due to corrosion but its making solid enough contact to the tube dag at this time.
The chassis solders and overall condition isnt bad even though there is evidence of moisture based corrosion in some areas


As of now the chassis fully energizes, heater voltage running, deflection sounds like its running, and the 15/24/31 khz relays cut over when I plug and unplug a Naomi from the chassis.
There is no static on the tube and no sign of HV but I havent put a HV probe on the anode to confirm its zero volts or very very low

I doubt the flyback is shot right? , because it would just immediately blow the HOT and or FET again because the FBT is helping drive the HOT.
Im wondering if I missed a fuseable resistor or a fuse or something weird.

Anyone got ideas, would save me some repair bill costs at the expense of more knowledge and my own time.

 

[wigsplitta]

If the chirping is continuous, like a clock ticking, there's a good chance you will need to replace the flyback. I've owned three of these, and they all failed at some point. I sent them off for repair, and each time it was the flyback (and possibly other bits) that needed replacing to bring them back to life.

 

[GeekMan1222]

If the chirping is continuous, like a clock ticking, there's a good chance you will need to replace the flyback. I've owned three of these, and they all failed at some point. I sent them off for repair, and each time it was the flyback (and possibly other bits) that needed replacing to bring them back to life.

The chirping was very clearly the board trying to kick start the deflection/HV block into action. Was like a clock ticking yes.
But replacing these parts fixed that issue.

I started to lean to this conclusion maybe the flyback is truly hosed.
Heres the thing though, my general understanding of how these circuits worked was the HOT was driven in unison with the primary winding of the flyback and helps drive the flyback and the flyback primary helps drive the HOT.
However maybe with this newer stuff maybe thats just not the case anymore and is the only thing FET driving the Primary.

But neither of these devices are blowing up again after replacing them...

I have a flyback winding tester in storage maybe ill pull the flyback off and test the primary winding and the Horizontal Deflection Circuit..

I went ahead and reflowed the ENTIRE HV and Deflection block and shotgun replaced the vertical IC as well since I was told they like to blow on these too.

Same result. Chassis is running normally, no more chirping, you hear the deflection running, heater is running, but no HV on the tube....