I think my Japanese PSU is bad?

[Ransom]

Hey guys,

So I was playing my Creativision one day around a year ago and it just died, video went blank. But when I toggled the power I did notice a flicker or light or something that made me think it was getting some.

Anyway, I opened it up and was surprised to find 0 dc on everything, so it didn't make sense it was getting some power at all unless there is something weird going on (for example, you can't test a Laseractive power supply unless you short certain pins or something)

My current thought is the power supply is hosed and I can try to make a replacement (being dc it shouldn't be so hard to get voltages we need...) but anybody thinks I'm barking up the wrong tree please let me know!

Pic of the power supply attached - also, I pulled out the power supply to see if anything has changed, it's still 0 dc on all pins but ... why does it show 2v ac voltage?! Thought that might be a clue or something, so here's a video of that: https://www.youtube.com/watch?v=PB9-IrGmN9A

[MADrigal]

Your PSU contains one AC-AC transformer with 2 outputs (or 2 distinct AC-AC transformers) and then a 'signal rectifier' that could be either made of diodes, or transistors that 'rectify' the AC into DC.
With the 'rectifier' being faulty, I speculate that some of the signal passes as unrectified. I have no clue why the central pin gets some signal, possibly a wrong soldering inside?
I believe the best thing you should do is to open the PSU (well, if it's broken, it's no use, so better trying to salvage it) and test the signal rectifier and all solderings. Also FYI my friend Giovanni once found a tiny fuse embedded in the transformer "spires", that was broken. He just removed and added a by-pass in the spire, and the transformer came back to life. This could also be your case: look for small fuses in the spires.

[Scouter3d]

Hi,

could you please measure the voltage between the two left most pins (16, 16) that may be 16V AC...

Cheers, TOM:0)

[MADrigal]

Hi,

could you please measure the voltage between the two left most pins (16, 16) that may be 16V AC...

Cheers, TOM:0)

I understood that he had tested pins 1-2 and 3-4 as DC but got zero on all. Is this correct?

[Ransom]

Oops, no I tested them wrong! I misunderstood the label. I had the negative lead on the N pin in the middle... I went and re-rested correctly...!

The two pins on the left: 19V AC
The two pins on the right: 11.7V DC

So while the values are a little high, I guess under load they probably come down a bit and are within acceptable ranges. I guess the power supply might be ok and the CreatiVision itself popped something. Looks like I'll need to open it up and prod around in there. Thanks for getting me on the right track.

[Scouter3d]

Hi,

yes, this looks much nicer ;0)

so the "N" on the label is "Not connected"
and "-9" should be labled "GND"

And yes, the voltages should drop a bit under load, and they are well within spec for the internal PSU parts...

The Creativision needs 3 voltages to work properly: +5V, -5V, +12V and it supplies around 9V to the cassette-port (if iirc)

But at first the supplied voltages go to the power-switch...


But let me ask first how you testet the CV?
Did you insert a cartridge? Without cart, you will get no picture / good videosignal (maybe clean the cartport and cart with isopropanol alcohol and plug the cart in and out a few times...)
switch the CV on and of a few times (maybe the switch is corroded a bit...)
Check the chanel tuning on your TV...


Next you need to open the console and check for the 3 voltages... best place to check are the RAM chips as the have all 3 voltages present...

dram_pinout.jpg

Cheers, TOM:0)

[Ransom]

Thanks, very helpful. Ok, I took it out and to my surprise, it actually turned on - for around ten seconds. Then it shutoff, black screen. If I leave it on, it kind of toggles on/off at kind of random intervals around 5 to 30 seconds apart.

I checked the three power pins on one of the 4116 and while it's "working" things looked ok except the +5 was showing +7. (it was +5 early in my testing but it actually changed over time, like the power is getting worse, uh oh) In "black screen" it drops to 0.3v or so.

So a power problem somewhere I guess. Maybe the culprit is the 17805P voltage regulator? It does show the output is +7 there, I assume it's supposed to be +5. In black screen mode its input drops to 3v or so, and output from the pin on the right drops to 0.3v or so. (see attached pic to hopefully make that clearer, I wrote measurements on the pic for both regulators, while it's working, and while it's "Black screen")

I measured the +9 pin from the power supply connector while in use and in "black screen" mode it does drop to 3v or so. Even when working it seems to be dipping down to 7V or so, maybe affecting the colors on the screen.

Was curious how many amps the plug was pulling total (the 17805P seems to be getting awfully hot...) so I have it running through a killawatt to show usage. While "working" it draws 0.30 amps (at 100v) and while "black screen" it draws much less, about 0.07 amps.

So hrm not sure what to do. Replace the 17805P? Could the power supply also be the culprit with undependable power under load? Could a bad cap/etc cause the voltage to drop at the plug like that? Any advice or further test ideas appreciated.

[Mobsie]

it’s off topic, but let me ask Tom. If we replace the 4116 like they do on the Colecovision then we don’t need these strange 3 voltages?

[Scouter3d]

Hi,

7.7V is very bad! the right side of the 7805 should always read 5V

could be it is only the faulty 7805 i would definately replace it.

where did you take the GND from for your measurement?
please meassure the voltages on the regulators in relation to their middlepin.

Naturally there could also be defektive caps or a half-broken diode...

Please post a big image of the entire PSU-Part in the console as i never have seen a japanese version...

My first action would be to replace th 7805

Cheers, TOM:0)

[Scouter3d]

Hi Mobsie, i will look into the "are 3 voltages needed" problem, i seem to remember at leat one additional voltage was needed somwhere else... i will check the schematic.
TOM:0)