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sickly Sixer, advice needed.

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Hi all,

 

my PAL light sixer is rather unwell. The machine runs games OK but the video output is all messed up. The picture is black and white, with color accasionally showing, as does the audio. The picture rolls then stabalizes. I have cleaned all the switches witch were pretty grotty along with the cart port and all seem good now. I'm using a known good power supply and RF cable, clean game carts etc(I also own a Jnr and 7800). Using the same CRT telly that is fine with the jnr and 7800. I have taken a video on my phone, will find somewhere to upload it ASAP and post a link, it's too big to upload here.

Any help much appreciated.

Best regards,

Chris

 

Oh right I'm in the UK so everything is PAL, console, TV carts etc.

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If I remember this right, then there is an adjustable coil in the RF modulator part of the PCB. You could try adjusting that.

 

Edit: did you try out the TIA chip of that console in a different, known working console?

Edited by 31336haxx0r

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If I remember this right, then there is an adjustable coil in the RF modulator part of the PCB. You could try adjusting that.

 

Edit: did you try out the TIA chip of that console in a different, known working console?

 

Thanks, tried the modulator, only other console I have is Jnr, has soldered TIA so can't try change.

 

Looks like a bad 7805 voltage regulator. I'd start there as they are cheap to replace.

 

http://datasheetrefe...tor-picture.jpg

OK thanks, this looks simple enough to change, will try and track down part, no Radio Shack here anymore & CPC is long drive.

 

Best,

Chris

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I'm thinking it's the TIA itself. You can try turning the color adjustment pot and see if that cleans things up, but I doubt it will. A bad 7805 will not produce any change at all on the TV. You can check the 7805 with a voltmeter. With the power adapter plugged in, you should get 9 to 13 volts to ground on one leg, 5 volts on the second, and 0 volts on the third because it's the ground.

While you're in there, check the ribbon cable that connects the two circuit boards. I had one break on me one time and the console went absolutely nuts until I fixed it.

 

You will have to set the color pot to match the replacement TIA. If you try swapping the TIA from another console, the colors will be wrong on both until you either adjust the pots or swap them back. At least it'll tell you if the chip itself is bad.

 

The 7800 also has a TIA IIRC (please correct me if I'm wrong!). My 7800 has all soldered ICs, though, and the 7800 is not easy to open without breaking something.

 

I have a TIA in my pile of parts, but the colors on it "roll" slightly. It's not something I'd install into a working console, but it would be OK for testing purposes. It definitely doesn't roll like your console does. :)

Edited by shadow460

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Thanks shadow460.

 

Checked the VRM with a meter, it's as it should be. Looks like it's the TIA at fault.

Are PAL & NTSC TIA's the same?

If so I could use that TIA you have spare.

 

Best,

Chris

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I'm not 100% sure if they are, but if you wanna try it, shoot me a PM.

Thanks shadow, bit of research and it seems the NTSC & PAL tia's have different pin-outs sadly.

If anyone has a spare PAL tia, I would be most grateful, probably could find something neat to trade.

 

All the best,

Chris

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Given the higher number of scan lines on a PAL display, I would guess the TIAs would have to be different.

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