Pentranic chassis screen jumps

[Retroman839]

But my test rig 2x wires on pin 14 …

 

[gunblade]

video ground to jamma only
field ground is earth
link the power supply earth and common

 

[Retroman839]

Looks like 2 wires going in at ground also on my test rig .

 

[Retroman839]

Just a little link wire?

 

[Retroman839]

I think I have like dirty power ?
My
Psu still off
But screen om

 

[Retroman839]

I think I have like dirty power ?
My
Psu still off
But screen has crazy lines shooting all over the place
I have linked psu earth and ground too and it helped but
No completly

 

[Retroman839]

Its reducing
But It’s like interfearance is coming from power into chasiss

 

[gunblade]

is this the same chassis that had the mod done or something completely different as that looks like a pure flat tube

 

[Retroman839]

is this the same chassis that had the mod done or something completely different as that looks like a pure flat tube

Same
Chassis

 

[Retroman839]

Convergence is ok

 

[gunblade]

yeah the picture is great, do you have a resistor at R768 on the neck card and what is the value of the resistor at R369

 

[Retroman839]

yeah the picture is great, do you have a resistor at R768 on the neck card and what is the value of the resistor at R369

Will take a look

Schematic says

R369 either 26” 3w 5.6
Or on a 29” 3w 2.7

I will look

 

[gunblade]

I think its not an earth problem but rather moire effect, I have only ever seen that once and it was when I was using wrong tube to test a chassis so I ignored it.
Its possible Rick or MKL may know how to mitigate this

 

[Retroman839]

 

[Retroman839]

Ok I will ask him ..

No resister at r768 of neck card

 

[Retroman839]

I think its not an earth problem but rather moire effect, I have only ever seen that once and it was when I was using wrong tube to test a chassis so I ignored it.
Its possible Rick or MKL may know how to mitigate this

Moire effect ….
I will send him a message ..

 

[gunblade]

i am not that experienced with the indepth mechanics of crt but i do know many later crt/chassis use a negative voltage for G1, older chassis tend to just connect the G1 to ground
I do not know if this is the cause of your issue or if its something to do with the resistor missing at R768 or something with the heater voltage/current

 

[Retroman839]

i am not that experienced with the indepth mechanics of crt but i do know many later crt/chassis use a negative voltage for G1, older chassis tend to just connect the G1 to ground
I do not know if this is the cause of your issue or if its something to do with the resistor missing at R768 or something with the heater voltage/current

Cool mate …
Most greatfull to have got this far ..
And I’m well happy to tone
Down the sub bright as the flyback and colours are compensating great on all black back ground games especially ..
Só I would be happy
To have like this …

I have sent Rick a message
On it
And asked on APif anyone has had moire effect …

Is moire effect is when you start talking posh?
😊👍

Happy to add a resister in
To kneck card to see

Anything we could Try with g1 I guess runs Risk of damaging chasiss .

 

[M K L]

Oddly the schematics on page 1 of this thread don't show the G1. Most likely it will be grounded (need a pic of the copper side of the neckboard).

R768 is across the 200V video B+ line and the G2. Reminds me of the 25" K7000 that has resistors (R214 and R215) across these lines while the 19" version doesn't. Not sure if it will make a difference but you can try.

 

[Retroman839]

Wil grab kneck pic now

In mean time a little vid of effect
4 May 2026