Black Screen

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By cobracon2

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11-03-2018, 02:22

I was in the middle of a game, when my PV-16 decided to freeze. I turned it off and back on. Black screen. Any ideas? I've only had this thing a week and it's my very first MSX. I kinda blew all available cash on this, a 1mb card, cables, games and a 512 sd cart. Sad

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By Grauw

Enlighted (7203)

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11-03-2018, 03:21

That sucks!

Does it work with the 1mb memory inserted? Then it's a RAM problem.

Does caps-lock still work, or the sound (key click, startup beep)?

Do you have any kind of diagnostics tools like a multimeter?

If you open it up, do you see any kind of issues like leakage around capacitors? (When you open it up, also be sure to take pictures.)

By cobracon2

Rookie (31)

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11-03-2018, 03:42

No sound from at all. Power light comes on, does not work with cart or the 1mb cart. The volt meter is in my bedroom with a sleeping wife Sad I will open it up and see if I can spot anything. Else I'll have to wait till morning.

By Grauw

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11-03-2018, 04:06

Hmm, looking at the Casio PV-16 wiki page the RAM is in slot 0, so I think it is detected before the expansion in slot 1, so it could still be a RAM problem. The easiest way to definitely exclude the RAM (2x µPD4168C-20) from possible causes is probably to desolder it from the board and try the test with the external memory again. But maybe there’s other, simpler suggestions to try first.

And ah, I guess this machine has no caps-lock LED. Always a good way to test if it is still booting and responsive. But the lack of sound is a similar indicator. If you don’t hear anything, it’s probably not a VRAM (2x TMS4416) problem, because the machine should still boot without it.

When you open it up by the way, be sure to also dismount and remount the CPU board, could be a contact oxidation problem.

When you have access to the multimeter I think one of the things you could check is the power supply, it should deliver 10V according to the wiki.

By cobracon2

Rookie (31)

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11-03-2018, 05:21

Thanks for the great information. That gives me a place to start.

By cobracon2

Rookie (31)

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13-03-2018, 19:34

Well I checked the power supply, that seems to be ok. Then I moved to the regulator and it is putting out 5.2 volts. So I checked all the caps and there is no leaks or bulges.

I tried to remove the cpu board but can't seem to get it off. Does anyone know if it is soldered on. I don't want to break it off.

Thanks in advance

By Grauw

Enlighted (7203)

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13-03-2018, 19:42

From the pics on the wiki page it looks removable, resting on two SIP socket rows. Maybe wriggle it loose with the help of prying a thin screwdriver between the board and sockets? Inspect the pins for oxidation after…

By cobracon2

Rookie (31)

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13-03-2018, 20:31

Well it's not budging. By the looks on the wiki they desoldered the board. Guess the next thing is to look for cold joints.

What are the most common parts that die on these machines?

By Grauw

Enlighted (7203)

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13-03-2018, 20:39

Mmh yes now that I give it a second look I think you’re right.

My general impression from the threads here is that RAM and VRAM are most common, then electrolyte capacitors, then logic ICs, then ROM. CPU, VDP and MSX-Engine don’t die so quickly. Luckily this is quite a simple machine so once the cause is found all the parts are easily replaced, except for the ASIC at the bottom (probably an MSX-Engine like IC).

By jltursan

Prophet (2102)

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13-03-2018, 21:31

Yep, the chip in the bottom is the MB64H131 MSX engine...and precisely is this IC what failed in a PV-7 I repaired time ago. It's the same chip used in the PV-16 and I predated it because the PV-16 was in a general bad shape and was not an objective (shame on me!). The PV-7 was badly damaged, most probably a blowed up PSU, I replaced also the VDP. Both failures generated black screen. I suppose the PV-16 would work the same...

Following the Grauw's good recommendations, you can also check if any chip is too hot to touch, specially RAMs. As Grauw suggested seems that VRAM is probably fine, the bad news is that if IIRC, the CPU board is soldered but you can try to touch their chips carefully.

By cobracon2

Rookie (31)

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13-03-2018, 21:34

Well at least the memory is on the main board, but my desoldering skills are lacking. Looks like I will have to practice on something else first.

Is the TMS4116-15nl memory chip a must match part? or can I use another brand as a replacement?

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