Horizontal Lines On Warmup

[Krankshaft]

I have a Toshiba 27" CRT purchased in 03 that has recently been doing something odd.

On powerup horizontal white lines are in the picture near the top of the screen. As the set warms up these lines drift away towards the top of the screen until they are no longer visible.

As long as the set is warm the lines aren't there so if I quickly power down then up I'm fine.

I'm thinking a capacitor issue here but where should I check?

The vertical deflection or the video section?

I always thought that capacitor related vertical deflection problems manifested themself as improper vertical deflection.

I have an ESR meter so I'll find the little bugger even if it's not bulging.

I gave the TV a few whacks and it didn't affect the picture so it's probably not a loose solder joint it could be a cold one though.

Thanks for the help in advance.

[Wizard]

Re: Horizontal Lines On Warmup

100uF drying out in the vertical circuit. Easy fix.

This is what causing the vertical foldover because the vertical boost flyback capacitor is not pushing out 48-50V kick to kick yoke back up from bottom to upper due to dried up capacitor feeding by vertical 24V-28V (direct to the vertical) via a diode to cap's + side while - side goes to the vertical IC internal transistor switch that temporily hook cap plus this supply for boost flyback.

It will KILL the vertical IC if left in that condition long enough.

Cheers, Wizard

[Krankshaft]

Re: Horizontal Lines On Warmup

Thanks alot!

I checked the 100uf 35V Rubycon 85C in the vertical circuit and it's ESR was 33 ohms. This board was impressive all top tier caps (Rubycon, Nichicon, Chemicon) I guess it's 85 C temp rating was the reason for it's demise.

It seems like Toshiba had the ingenius idea to put both the Vertical output IC and HOT on the SAME heatsink.

This cap was merely 1/2" away from this heatsink so it probably was baked.

I replaced it with a GP KMG Chemicon at 105C (all I had in 100 uf at 35 volts) so hopefully it will survive since it's a higher temp rated cap.

Replaced it and I'm back in business .

[Wizard]

Re: Horizontal Lines On Warmup

That's not toshiba chassis, toshiba never put vertical and horizontal stuff on one heatsink. White label for model # on back, citizen chassis.

True toshiba chassis is yellow label.

Cheers, Wizard

[Krankshaft]

Re: Horizontal Lines On Warmup

I never knew that I guess my Toshiba branded RPTV with the white label on the back is Citizen as well.

Already went through a set of convergence amps on that one .

[Wizard]

Re: Horizontal Lines On Warmup

Not always

I know Citizen doesn't make RPTV.

If youi have pics of chassis, I might able to ID.

Cheers, Wizard