CreatiVision with distorted output then crash

Discuss the CreatiVision hardware: models, revisions, fixing, hacking and modding.
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cheshirenoir
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CreatiVision with distorted output then crash

Post by cheshirenoir » Wed Dec 16, 2020 3:55 am

Hey all,
My CreatiVision seems to have developed a fault, and before I start ripping it apart, I thought I'd check if any of you have seen this issue.
On bootup it's fine for a few minutes, then the picture starts to distort and the speaker makes a loud buzzing noise.
The best way I could describe the picture is the top starts tearing and showing a rainbow sheen over the top of the picture.
After this starts, it quickly crashes.
I assume something must be heating up.

Anyone seen this? (Trying to narrow down my test surface). If not my planned attack is as follows:
  • Check power rails
  • Check heatsinks
  • Replace capacitors
  • ???
Cheers!

Chesh
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Scouter3d
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Re: CreatiVision with distorted output then crash

Post by Scouter3d » Wed Dec 16, 2020 7:06 pm

Hi Chesh,

your check-plan looks good!

I would start with the external PSU (maybe it delivers too many volts AC?), then the internal PSU part (Bridge rectifier Diodes, Caps and the 3 Voltage regulators)...

I had something similar on a Salora Manager, that i povided with -12V instead of -5V ... worked for some time than got to hot and the voltage regulator acted realy weird...

Good Luck with the repair!
TOM:0)
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cheshirenoir
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Re: CreatiVision with distorted output then crash

Post by cheshirenoir » Thu Dec 17, 2020 1:10 am

Thanks Scouter3d,
Hadn't thought of the internal voltage regulators!
(May swap them over with a minature switchmode 7805 replacement)

Chesh
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Scouter3d
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Re: CreatiVision with distorted output then crash

Post by Scouter3d » Thu Dec 17, 2020 2:54 pm

Hi Chesh,

you are welcome :0)

the CV has 3 internal regulators (+5v, -5v, +12V) switchmode alternatives sound very good!

Greetings, TOM:0)
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cheshirenoir
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Re: CreatiVision with distorted output then crash

Post by cheshirenoir » Tue Dec 29, 2020 5:17 am

Well, I finally got the Wizzard on the bench again, and the voltages look within what'd I'd expect the tolerances to be.
The AC is putting out 17v unloaded on the 16v line and 10v unloaded on the 9v line.

On the inside, measured at the pins for the 4116 RAM I get
+5 = 5.02
+12 = 11.9
-5 = -5.2

This last one is the only one that's not exactly where I'd expect it, but should be well within tolerances. Any suggestions where to check next?
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cheshirenoir
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Re: CreatiVision with distorted output then crash

Post by cheshirenoir » Wed Dec 30, 2020 2:50 am

OK so more info. I think I must have a dry joint somewhere, so I'll pull it apart and see what I can spot. When the distortion starts, if I give the unit a tap on the top, the distortion goes away. Hope it's not below the lower shield.
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cheshirenoir
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Re: CreatiVision with distorted output then crash

Post by cheshirenoir » Wed Dec 30, 2020 4:22 am

Well, it looks like it WAS a dry joint. Went over the board with a magnifier, marked all dubious looking solder points and went and resoldered all of them. There was a "bodge wire" that was particularly loose, between the lower RF shield and ground, so I wonder if that was my weak point.

Chesh
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