Hantarex Polo 33" problem

[sevenleaf]

Hi,

I have a problem with the monitor in my Ridge Racer. I powered the machine up, and heard some crackling / fizzing coming from the monitor. A minute later, the picture started scrolling. Here's a picture and a link to the video.



http://img190.imageshack.us/i/mov02703.mp4/

I'm not going to have the cash to get someone else to fix this for a little while so I thought I'd have a go at fixing this myself. After all that is part of the appeal to me of owning and restoring an arcade machine - whilst learning on the way.

I've spent hours searching the net and staring at the chassis and found this (potentially) really helpful document:



Having watched one of Randy Fromm's videos on youtube I diagnosed a vertical vsync problem, and after I found the above document I identified and replaced T110, T112, C149, C150 and IC104 plus I cleaned the HV lead as I though it may have been arcing and blown a component.

However neither of these 'fixes' have made a difference so it's back to the drawing board. I'm not sure what to do next - but a closer listen to what I previously described as 'arcing' could actually be clicking - and it sounds as if it's eminating from the yoke?

So the top right box in that diagram sounds like a good place to investigate - althought I have a picture.

If none of this works, the final option (before paying someone to do it) is to confront my fear and start testing for voltages on the board.

Any comments welcomly received.

...edited to fix link...

[Nipedley]

I had a vertical scroll problem on a hantarex mtc 9000 (polo predecessor) and it turned out to be a faulty transistor, I replaced every transistor on the board at the same time out of desperation so I can't say which one.

I take it since you've replaced components you've already tried playing with the Vertical Hold. control?

[grantspain]

the sound of a crack would lead to suggest that it should be possible to see the faulty component,imo it could be the vert deflection ic 103 or a number of components around that

[sevenleaf]

I had a vertical scroll problem on a hantarex mtc 9000 (polo predecessor) and it turned out to be a faulty transistor, I replaced every transistor on the board at the same time out of desperation so I can't say which one.

I take it since you've replaced components you've already tried playing with the Vertical Hold. control?

That's worth a try - you're the first person I've found that's had the same problem as me.

I haven't tried the vertical hold control for a few reasons:

1. The problem 'just happened' so I can't think that it's a calibration problem.
2. The clicking makes me not want to touch the monitor whilst it's live!
3. I don't know which control is for vertical hold.

the sound of a crack would lead to suggest that it should be possible to see the faulty component,imo it could be the vert deflection ic 103 or a number of components around that

I was hoping you would reply! I found many of your very knowledgeable posts on different forums whilst researching this problem.

There is one round component that looks a bit 'flakey' - it's the reddish thing behind that 'stand up' board, with the black screw on top of it. You can just see in the photo that the paper looks as if it's lifting a bit.



There are also some signs of overheating on the bottom of the PCB - but I have no way of knowing whether they are old faults that have since been fixed 



PS - I can't find schematics or TP voltages for the 33" monitor chassis ANYWHERE - can anyone help?

[grantspain]

the 33" chassis is in essence the same as the 25/28" for layout-only the flyback and few components will be different
ok so tracing v freq goes to r169 then into ic103(tda 1675) also check d128 and r168
personally i think ic103 is shot and you will need to check 25 v dc at tp 31 for being spot on 25vdc
also i think someone mentioned to check the pots on the remote board as they are a common fault

don't worry about the discoloured board as thats quite normal with polo chassis

is is still making the noise when you power on?

[sevenleaf]

Thanks Grant! I have ordered a replacement TDA1675 and will also replace BU508A at the same time as I have read they work pretty hard and can fail.

Re voltage testing - I don't have a test rig and feel apprehensive about testing whilst the chasses is tucked under the neck due to the extreme voltages and tight working space. Do you have any tips for me here?

It will be a couple of weeks until I post back with results as I can only work on the machine at weekends as I don't have it at home - plus I have to take the chassis to a mate to solder it for me which adds a week onto repairs.

Many thanks once more for your continued assistance!

[grantspain]

yeah if you do not know what you are doing tbh its not worth the risk of reading voltages,replace those two components and see what happens

[sevenleaf]

Changed those 2 parts, made some tweaks to the pots and the picture is as sharp as ever! Clicking has ceased too. Result! Thanks everyone for your help, especially grant!



Now for the broken Sega Rally upright I've just bought...

[grantspain]

result