Hantarex Polo 25 - Top Wobble

[PappaLazarou]

Hi All,
Just putting together a point blank can I bought a few years back which I’ve replaced the fly back all recaps and most film caps. The colour and picture looks pretty good overall but I can’t seem to get the grid pattern to align at the top of the screen. When i try and adjust it it’s super sensitive but won’t go straight. I’ve disconnected the degauss coil as I’ve read that can interfere if it’s faulty. Has anyone else come across this wobble at the top of the screen?
Cheers, Mike.

 

[Retroman839]

Could be a cap in vertical deflection circuit going bad. Or could a new cap in that circuit be wrong way round /out of spec cap.
bad contact broken trace.

cold solder on the vertical ic ?

 

[gunblade]

does the vertical lin pot function?
does horizontal shift work and horizontal freq?
is b+ between 138 and 145?
is it affected by vertical size adjustment?

 

[PappaLazarou]

does the vertical lin pot function?
does horizontal shift work and horizontal freq?
is b+ between 138 and 145?
is it affected by vertical size adjustment?

H-shift and H-freq work I.e. they have an effect on pic when I turn them. B+ is 138.5V
I’ll check what happens on V-size change.
I’d not tried V-lin pot - I’ll pull the chassis out and see if it adjusts.
Cheers,
Mike.

 

[gunblade]

you would need to adjust v.lin while powered on
its a bit of an odd fault, it could be something to do with the vertical ic or circuit or could be a sync issue

 

[Retroman839]

Was reluctant to say
Because the distortion is Só butifully uniform looks to be made in circuitry.

Long shot but some times this kind of magnetic distortion can be an outside interfearance.
Have you tired moving the cab to see if it changes ?
From outside interfearance.

Also just check a ac chord isn’t passing to close to top of the tube for the top marque light.

 

[PappaLazarou]

I’ve tweaked V-Lin POT and it does affect the linearity but the wobble is still there. While I had my arm in there I also turned the 2 POTs on the east-west board and they work as well although not a massive range of adjustment. Using the TPG the wobble is less pronounced than when a test pattern from a game is used.

 

[gunblade]

just hsync connected?

 

[PappaLazarou]

just hsync connected?

I’ve got sync and vsync tied together at the Jamma video connector

 

[gunblade]

disconnect vsync yellow wire

 

[PappaLazarou]

Disconnected yellow wire but no visual change

 

[gunblade]

do you have a jamma board you can try

 

[Retroman839]

Thin plastic guide missaligned


Will need thin plastic guide correctly positioned so it slides into groves then connection will go all way down.


Could it be Riple getting in to vertical circuit , from bad smoothing caps in secondary of the power section.


Try Disconnect demag coil
Ptc stuck on

 

[PappaLazarou]

It’s the same with or without the degauss although I definitely need a new ptc as it doesn't fire from cold start. I changed pretty much all the caps (film and electrolytic) for tier-1 brands like Rubycon and Kemet etc

Other than the HOT when I fitted the new fly back I’ve not changed any other ics, diodes, resistors or transistors on this chassis so could be something there too.

I’m going to have another look tomorrow - I’ve got a donor polo/2 chassis and I’m pretty sure I have a spare vertical ic somewhere so will have look and feedback.

Cheers,
Mike.