Sega Rally - screen problem

Hi all, This weekend I went to collect a Sega Rally upright arcade cabinet.
The game and controls are all in good working order. The only problem I am having is that the screen seems to have a blank area of about an inch along the top of the picture.
There appearers to be some thin white lines right below the blank area, and the missing part of the picture is displayed very faintly upside down within the area of lines. The rest of the picture is great and spot on.
Here is a short vid of the problem:

http://www.humyo.com/F/9191346-454458565

I haven't done much fiddling with anything yet. I would be glad of any advice if anyone has seen this before.

 

Just looks like the screen might need adjusting, most Sega games have a Nanao chassis so the controls are likely to be at the front under the tube. Go into test mode and select the grid pattern to adjust the screen.

Use plastic trimmer tools to make adjustments. Generally you will need a flat balde plastic one for most of them and a hex one for the H-Size coil. Don't use metal ones just in case you touch something you shouldn't and using an allen key to adjust the coil will make it hot and could damage it or burn you (seriously).

Make small adjustments to the position and width adjustments and sometimes frequency if the picture doesn't seem to want to move exactly.

If you still see small white lines, then the screen brightness need adjusting, this will be at the back of the chassis and will require a mirror or someone to help you, it will say "SCREEN" on it and make small adjustments until the black is black.

 

The screen image just sits under the blank area. In other works the Blank area stays in exactly the same place and is impervious to the front adjustment pannel.
I can always shrink the picture down and not use the top of the screen.
Sorry if the video is hard to see.

 

Sorry, are you suggesting it's an issue with the monitor rather than the image? i.e. the white line remains in the same place despite collapsing the image or changing it's dimensions on screen?

 

That's right. Regardless of how the picture is tweeked the black area shows nothing.
Slightly under that I can see what should be in the blank area, but inverted with faint lines in it.
You can see on my video from about 10sec in that when the car passes out of the vally there is the missing part of the picture inverted over the regular one. it's best seen with the tops of trees and the buildings.
Here is a photo of the test screen

It might help if I found a service manual for the monitor, but I can't see any make or model on there.

Here is the rest of the setup


What are the things that look like sliders around the slim part of the monitor tube neck before the PCB?

 

They are the convergence rings, don't touch those unless the colours are seperating.

So you adjusted all the settings including V Freq? Adjust this and see if the folding stops.

The chassis looks like a Nanao MS8 26 series chassis, if you remove the glass and bezel of the arcade you should see Nanao around the controls. The chassis doesn't have a flyback failure, so it should be repairable as these chassis are hard to get replacement flybacks and annoyingly the tube won't work with any other chassis.

 

I have played with all the setting on the front pannel. The more I adjust the picture to make it higher, the more it folds back on its self.

This poor machine is very used, and has had little attention for a very long time.
Would I be able to replace the whole screen with a CRT TV of the same size. I did this in by MAME cabinet with great sucsess. Would a scart TV be able to sync to model 2 resolutions?

 

Umm, you didn't take a photo of the slim part.... :110:

Yeah, don't touch them. In fact, I would advise against touching a monitor if you don't know what you're doing. And if you decide to proceed, do so with the usual cautions (I've mentioned before).

I would need to know what the monitor is. Can you (carefully) take a picture of the chassis? It does indeed look like a Nanao, though.

I wouldn't recommend putting televisions in arcade cabinets. Not wise, and not attractive!

 

When I get home I will remove the glass front and try to find the model number.

With the TV in my MAME cab, I removed it from the case and mounted it in the original hanger. Looks exactly like an arcade monitor, just with a scart connector on the mobo. I used a 20" CRT Sony Trinitron. I would need somthing much bigger for this
The best thing would be to get this working.

 

Model 2 games require a 25Khz monitor, which basically means you can't use a TV and you can't use a VGA monitor.

There are two knobs which will cause the picture to tear and bend if you move them too far, if you have touched these and the top of the screen is still rolling over then you will need to get the chassis recapped as it sounds like everything else is working.

 

Recapped as in capacitors?
I did find a thread on another site saying that a set of bad caps can cause Foldover.
I am quite good with soldering and would be happy to have a go. The only problem is discharging the tube. That scares the hell out of me!
Some places say its easy, others say its not and never do it.

Can you just clarify somthing for me; the chassis is the monitor motherboard right? and What pat is the flyback?

 

Right, just got in from work and set about removing the glass and plastic surround. I had a much better view of the adjustment panel with labels.
I switched it on and even more of the picture was missing, It now seems to have been getting worse every day.
as I watched the picture collapsed into a white line :banghead:
behold the mighty line!

as I was there I got some better pics of the board

I still can't see a model or make. but it does look like a Nanao MS8 26 as seen on google.

 

You've lost vertical deflection. That's probably the vertical output chip. However, you need to measure the voltage at the power pin on the chip before just replacing it. Hopefully the voltage won't be there. You'll find an inrush current resistor before it - usually around 1.2 Ohms at 1 or 2 watts. That might well have gone open, so test that too. Then you replace the resistor if it needs it, then measure the resistance from the power pin of the chip to ground. That should be high - if it's low then the chip is bad. Change the boost capacitor at the same time.

Talking of capacitors, you'll probably need to do a cap job, i.e. replace the electrolytics. You can usually get cap kits for your monitor from arcade suppliers (e.g. Swallow in the UK or Bob Roberts in the US).

Yes you need to discharge to do any of that, and you need to treat that seriously and take all the proper steps. Look at the tips I gave elsewhere on the arcade forum. Oh, and I CAN'T BE HELD RESPONSIBLE if you zap yourself! You shouldn't mess with this stuff if you don't know what you're doing. I'll give you advice, but it is down to you if you go ahead and play with monitors.

The LOPT is the flyback transformer. Follow the cable from the suction cup back to the LOPT.

 

http://www.arcaderestoration.com/index.asp?OPT=3&DATA=10&CBT=2

On the above page the guy talks about the same problem you have i.e a missing band of the screen and is giving advice on discharging a monitor.

Again it's only advice, if you die, not my fault but best of luck.

 

Thanks retro, Jamtex, Parris and Twimfy.
I have send an email to the guys at Swallow about the cap kit. I'v read every thing I can find on the discharging and I'll give it a go. I'll let you all know how it goes, If i dont fry my brain that is

 

Discharging is easy, although still dangerous... I've seen people discharge monitors using two screwdrivers and the metal frame, but this might not discharge correctly. If you do get a shock it will feel like someone has hit your elbow with a sledgehammer and you might fall backwards, so make sure you have enough space around the machine and nothing sharp is around and you have someone nearby.

You will need a plug, a 10 Megaohm resistor in the largest wattage you can find (1 or 2 watts should be fine), some earthing or mains cable pref at least 2 metres, heatshrink tubing and a large flat blade screwdriver and when I say large I mean large, the ones that have a chunky 1.5cm end and are about a foot long with a thick plastic handle, get a brand name like Stanley.

1 - Open plug, remove the live and neutral pins

2 - Get wire and strip one end slightly

3 - Solder resistor to one end, cover with heatshrink across the whole body of the resistor, but leave a little off one end so you can put it into the earth pin of the plug,

4 - Use a hairdryer to shrink the heatshrink tube and then tighten up and close plug.

5 - Strip as much off the other end of the mains cable

6 - Wrap wire end around the metal end of the screwdriver, near the centre, you can use some tape to hold it in place if need be, but you shouldn't have to

7 - Plug the plug into a mains socket, don't switch it on.

8 - Put one arm behind your back

9 - Put screwdriver under the rubber cap at the top of the monitor

10 - Push it to the centre, you may hear a crack or you may hear nothing

11 - For safety wait 30 minutes and do it again.

12 - It should be safe and you should be able to squeeze the cap off the monitor tube and unplug everything, but do it slowly.

13 - To discharge the caps, just a smaller screwdriver and touch each end of the cap, use common sense as most of the small caps will not have enough charge to do any harm, ie if it's rated less then 25V and under 1000uf it's likely not to do anything, most monitor chassises do have bleed resistors so they should be safe,but better safe then sorry...

The Nanao monitors tend to blow a fuse if they do suffer from total frame collapse, but I suggest you do get the board repaired professionally, but you could try a cap kit if you feel poor. Just make sure you note the polarity of every electrolytic cap as they tend to blow up violently if plugged in the wrong way (well some will just go pop but the high voltage ones will cause a nasty mess and possibily blind you if you are looking at it as you turn it on...)

 

Umm, no. NEVER discharge directly to mains earth. Discharge to the frame of the monitor.

There's debate over using the resistor - on modern raster monitors, it shouldn't be necessary. Remember that doing so will take longer to discharge. There's no harm in doing so, though.

IF you're going to use the screwdriver approach, DO IT PROPERLY! Don't wrap a wire round the screwdriver - that's asking for trouble. Drill a hole through the screwdriver, put the wire through and solder it. Then on the other end of a cable, put a clip (like a car battery clip) to go to the cage.

The proper way would be using an HT probe instead of a screwdriver.

 

Loved this post!

As for thanking me, I don't think I contributed very much lol - I hate monitors. HATE, HATE, HATE them - they are the bane of my life (when faulty) and don't like giving any half-assed advice for the very same reason as above.

Retro's advice on the discharge warning is crucial. Seriously!

The list of what to do is good though, just that bit about the screwdriver is important!!!!!

 

BTW, I love Sega Rally - what's the cabinet like taken from the front? Was this an eBay item?

 

If you are going to be cheap and use a screwdriver instead of an HT probe, then PLEASE listen to one of the experts - Bob Roberts:

http://www.therealbobroberts.net/sb.html

He also reiterates what I said about winding cable round a screwdriver, and talks about the use of a resistor.

A lot of people say to completely unplug the cab before discharging. Some say leave it plugged in (and hence earthed). It's open to debate, really. I've asked friends who were television engineers and they all say different things! The majority say unplug, though.

The most important thing to remember is NEVER use both hands on a monitor - keep one in your pocket!