Hantarex Polo 28 No Picture

Jon-A-Tron

Jon-A-Tron

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[font="Verdana, Arial, Helvetica, sans-serif"]Update[/font]

[font="Verdana, Arial, Helvetica, sans-serif"]I've had a play with all the control board potentiometers with no luck. The H.Freq and H.Phase seem to work as expected but the H.Amp does not. At its lowest setting the picture becomes distorted in the centre of the screen. At the opposite scale its far too wide. I measure the change in voltage being outputted to the main board by the control board and was getting an even change from 0v to 12v, so no issues with the pots.[/font]

[font="Verdana, Arial, Helvetica, sans-serif"]I moved onto the pots on the E-W board. RV3 and RV2 seem to work together to centre the screen in much the same way as the control board does. Neither of them reduce the screen width. I didn't want to adjust the other pots on that board as the manual says they are factory set and I don't think they are my problem.[/font]

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After a bit more searching I found another forum post about a 'retrace tuning capacitor' being in parallel with the HOT collector-emitter and being a value of 5,000pF to 10,000pF. This capacitor controls the width of the picture with smaller values making the picture smaller and larger increasing the width. Those values looked right for my problem I had when I removed C99. The value I had was 8n2 (8,200pF) and the diagram said I should have 7n5 (7,500pF) for a 28". Could this be my retrace tuning capacitor?[/font]

Does anyone think I might be looking in the right place for this? Or am I missing something else to check?

I'll order a 7n5 2000v and see what difference it makes anyway.

I did fit a new coin door light to give me a sense of achievement this weekend though..so..
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tb2000

tb2000

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That swapping of caps for picture width is ok on older chassis like G07 etc. to a certain extent but I wouldn't go doing it on something like a Hanty as it was designed with those caps in the circuit, you might put undue stress on other components changing them like that Plus with the chassis working 100% you wouldn't need to swap them for anything other than what's in there anyway!
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obcd

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Are you able to adjust the pincushion with it's potmeter?

The circuit responsable for that has influence on the image width as well.
 
Jon-A-Tron

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Adjusting the pin cushion pot has no visable change on the screen that i can see. Didnt check the voltage change on this though so will try that when i get home. JonTron2016-11-14 13:30:35
 
tb2000

tb2000

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If I remember correctly the main presets for pincushion etc for cga/ega/vga are on the upright east/west board in the middle of the chassis. With that said, unless the previous owner has messed with them they shouldn't need adjusting.
 
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obcd

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If the pincushion correction circuit has a fault, it can also cause a picture that is 2 large. That's why I asked if the circuit is working which can be checked by changing it's adjustment. If nothing changes with that adjustment, fixing the pincushion will likely fix the image width as well.
 
myPinballs

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Ressurecting an old thread, i am looking at a polo star 28" out of another silver strike bowling, The HOT was shorted so i replaced. Now the ticking is gone and i get neck glow but no static on screen and no picture. The b+ (measured from this yoke black wire loop point) starts at 183v and then drops to around 160v. I'm guessing this is too high and some cap needs changing but i'm wondering which ones.

I'm gonna pull the chassis back out and take some of these hv caps out to near the hot section to measure them

Any thoughts?
 
myPinballs

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So i found a shorted mosfet on the switch board at T6 (IRF630), that i think was mentioned in another thread. I changed this along with T4 and T7 for IRF640. I also replaced the HOT again even though the other new one was still testing ok.

Also replaced C17,C18,C25 on the main board (from another thread) All originals tested ok.
I removed and checked C101, tested ok at 1.43nF, case said 1n5

Plugged back in first time, nothing same as before, no picture, no static but was neck glow again.
Second time thought i'd measure the b+ voltage again and also the G2 on the neck board, but didn't get chance because the flyback killed itself and started sparking like fuck from the top. Nearly had a heart attack!!

So need to know what the part number for the flyback is and i'm about to dismantle again and see what else is dead. Tricky blighter this one but i will get it working haha. Any other thoughts welcome
 
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Ace`

Ace`

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Pretty much everyone offering new flybacks is having them made super cheap in China unless they happen to have some new old stock ones. There's a couple of sellers in the States that offer them but they know what they're selling so send out a replacement if it doesn't last long or arrives DOA. What's the story with teknoservice?
 
myPinballs

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Update on my monitor repair.

Success, new flyback sorted it. I decided to try the techno-service ones anyway. All seems good to me. Easy install, good picture and easy adjustment of screen and focus

So to summarise, the problem was shorted hot, shorted T6 on the switch pcb and bad flyback.

I also went through every hv poly cap ,removed, tested the values and reinstalled if ok. All were in spec (10% ish) and i also changed all the hv electrolytic, again all the originals were still in spec. I have the readings to share later.

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