Hantarex (Sambers) Polo 28 MF video problems

baritonomarc

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Hi all,

i am trying to figure out what is wrong in my Hantarex Polo 28 MF (dual frequency).

The monitor shows the image, does not go hot, B+ is a stable 142 V DC and voltages are correct (i measured B+ on one leg the white ceramic big resistor, TP9 → 15V, TP10 → 12V). Replaced C112 and C114 since i had them and are known to be faulty caps.

The following images can give an idea of the prob:

sam0961slim.jpg


sam0956slim.jpg


Essentially, it's almost impossible to get rid of those raster white orizontal/diagonal lines (even toying with the flyback knobs or the brightness/contrast pots... they are responsive, the lines can be heavier or lighter but they stay there).

As you can see, another problem is that the brigtness is different in different regions of the screen.

In addition, there's a 2 inches tall white horizontal bar on top of the image

sam0948slim.jpg


… and the image shakes heavily vertically (non interlaced signal).

Could anyone suggest me what to check?

Thanks :)
 
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Just to summarize the probs on this monitor:

- raster lines are always there, even if the Fly knobs are responsive
- without video signal the image is white, not black
- the image shakes vertically
- brightness is different in different video zones
 
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Being the image there, the B+ correct and having no (apparent) horizontal deflection problems, my inspections have been driven in the vertical deflection and video amplification circuits. I have done a cap kit (only electrolitic caps) of those 2 circuits, checked the resistances and diodes of those circuits and i am now waiting for a spare IC1 (video amp IC).

Hope this will solve the problems of the monitor, i will keep you updated :)
 
Let me link the manual, just for reference :)

http://www.andysarcade.de/data/coinop/videogames/raster monitors/hantarex/polo_25/polo_25.pdf

Yesterday IC1 was delivered to me: i installed it and i substituted T1 also. Nothing changed: all the probs are still there :_(

I also lost the "blue" on my image, but turned out to be a bad solder, now fixed... my bad.

Do you think that changing the vertical deflection circuit (IC103) could be of some help? What do you suggest me to do at this point (apart from trash it :)) ?

Thanks
 
More to Check

C181 may have replaced already.
c166 and c130 or the caps for ther 12v regulator
Check ohms R36 the 270 ohm resistor for the G1 on neck board
And replace c14 on neck board
did you get the cap c401 on the remote board replaced?
The dark board makes it hard to see the TP's
but they are there and On schematic
Tp30 or at c181 for, -190 dc to T115 and T116
make sure d144 and r230 are good.
read ohm on R233 100k and r240 for 180k, really any high ohm resistor
in that area of schematic to make sure not increasd in resistance and
resolder all connectors on remote board and main pcb.
Any hairline cracks in the flyback around screen and focus pots?
 
Yesterday i gave a check to diode D1 and resistances on pin 14 of IC1 (R8-10, R35, video amp circuit): they all measure good :_(

C181 may have replaced already.
c166 and c130 or the caps for ther 12v regulator
Check ohms R36 the 270 ohm resistor for the G1 on neck board
And replace c14 on neck board
did you get the cap c401 on the remote board replaced?
The dark board makes it hard to see the TP's
but they are there and On schematic
Tp30 or at c181 for, -190 dc to T115 and T116
make sure d144 and r230 are good.
read ohm on R233 100k and r240 for 180k, really any high ohm resistor
in that area of schematic to make sure not increasd in resistance and
resolder all connectors on remote board and main pcb.
Any hairline cracks in the flyback around screen and focus pots?

Thanks for the help, i will check every single thing you suggested and i will report :)
 
Every single point have been checked in the last few days and i found:

- R36 open - replaced

- C166 and C130 capacity reduced by 30% - both replaced

now the retrace lines have gone and with no signal i have a carbon-black image :)

The only problem persisting is the annoying vertical vibration, much more visible with low-res non-interlaced images. As said, all the caps on the vertical deflection circuit have been replaced, the resistances checked...

What do you suggest me to check at this point?

Thanks A LOT
 
Change all the caps!

Great,
I would suspect first C125,C150,vr401
Low 12vs from Ic105
Bad connection to vertical Ic or Ic
bad grounds in and around remote board.
Maybe Misadjusted VS,VA,VL,VF all vertical pots.
Should replaced all the electrolytics and confirm they match up with the schematic.

I replace everytime i get a fresh chassis is Fly,HOT,all radial cap's
and the rectangle box caps in High voltage,vertical ic
rebuild the solder on the high watt resistors,and components pins
mounted to heatsinks for good connections to H-driver transformer, ohm out traces for
opens around overheated parts.Then i test for any problems.
Good Luck with the repair.
 
Thanks for the reply :)

Just made some "half-way" repair and test:

- C125 and C150 had been already replaced
- VR401 is ok
- 12V are perfect (11.98 on J117)
- apparently there are no ground problems on remoteboard

Even if ESR tested good, i replaced the big filter cap (220 uF 400V) with a 330 uF 400V i had by hand... not sure if this can cause the new issue the monitor has :_(

... essentially when i turned on the monitor the first time the image was 2-3 inches wide (and centered). Then started to vary the width from that initial reduced width to maximum width, then stopped at the maximum width. RV404 was no more responsive (even if tests good on the bench). I noticed that the bigger the width, the higher the vertical oscillation!

I hope that at least the new problem will help you guys diagnose the problem sigh sigh :_(

Thanks for the help
 
Replacing the big filter cap with one of the right capacity did not solve the vertical shaking problem, nor the loss in horizontal amplification :_(

Probably i screwed the BDX53A (i have a B-C short in circuit, even if it's not shorted out of the circuit).

I should have a non working polo somewhere to use as source for that Transistors and have a quick check.

Just to summarize the probs the monitor has :

- vertical shaking
- max horizontal amplitude, no matter how i turn the H.amp. pot (it has no more effect even if tested good)
 
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Replaced IC103 (vertical deflection circuit) just to see if it's the cause of the vertical shaking and BDX53A with a used BDX53B i had by hand to have back the amplitude control (resistances R247-253, 226 and 243 tested good). As son as i will be home i will replace a couple of capacitors that where waiting to be replaced (even if tested good at the ESR) and then smoke test... finger crossed :)

Noticed that instead of the 8.2nF 1500V reported on the manual, C174 is a 4n7 in parallel with a 5n6 cap on my polo... maybe a previous repair and hopefully a possible cause of the vertical shaking.

As always, any help/advice would be very appreciated :)
 
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OK, found D135 shorted: replaced and the hori amp is there... hurray! :)

The monitor still suffers the vertical shaking... not sure what to check now... :_(

any advice?
 
OK, found D135 shorted: replaced and the hori amp is there... hurray! :)

The monitor still suffers the vertical shaking... not sure what to check now... :_(

any advice?

The bad damper diode and pincushion amp parts is because of the POLYs
The diode is in the HV Damper circuit and when it shorts
the Retrace and safety caps have fail and
the High voltage regulation is all out of specs, the Polypropylene
caps controls the P~P Pulse or high voltage current thru the fly and yoke etc.
when the caps fail it shoot alot higher causing excessive current
thru the HV parts, The way it sounds with your repair is you also have the wrong
parts in the chassis need to put back the correct parts.
Need to replace all at once for best results.
Can use Metallized polys or both type.
If you keep holding off with the HV repair it will take out more parts,again
and again..
 
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Thank you very much Ohmerone for the help

i am experiencing some difficulty to find out those rectangular shaped poly caps, but i have by hand some of this caps:

sam0973slim.jpg


In particular, the pictured is the one i wanna use to replace C174 ... is it ok?

thanks
 
Some news :),

replacing the safety polypropilene caps and another 2 polys close to the HOT did not solved the vibration problem. I then decided to use some different signal source (when you have no other ways, go back a little and double check the obvious ;)) ; i was using a PC forced to 15KHz with Calamity drivers and JammASD, s a "complex" source: i then put in a neo geo 1-slot motherboard... perfectly stable image! I then used another PC to check if the problem was in the JammASD (very unlikely: that PCB is rock solid even after years of work) and the image was... perfectly stable again! So,in the end the (vibration) problem was the PC i was using...

lesson learned (again:)): always use a simple and reliable signal source for your testing !!

Thanks A-LOT to all of you helping me, in particular Homerone for the precious hints on what to check
 
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