MSTE screen flickering after being ran for awhile

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christos
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MSTE screen flickering after being ran for awhile

Postby christos » Tue May 09, 2017 4:59 pm

Hi,
I've got this issue with my mste. After I run it for a few minutes (15-20) the image starts flickering left and right (but not up and down). Any idea what it might be? Also, it seems like my cache chips have an issue since the machine halts when I turn them on.
Thanks in advance.
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Re: MSTE screen flickering after being ran for awhile

Postby christos » Fri May 12, 2017 3:49 pm

Update,
I thought it might be the shifter overheating so I decided to check by putting a heatsink over it. If it took longer to cause the issue, I would have found the culprit.
However, the machine never started after that. It powers on but all I get is a black screen and a buzzing sound from the monitor port. Connecting with the L&R sockets doesn't produce the buzzing. I thought it might be that some thermal paste leaked in the socket so I removed the chip, cleaned it up and the socket with some isopropyl alcohol but there was no difference. I also reseated the rest of the socketed chips. No result. Any ideas?
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Re: MSTE screen flickering after being ran for awhile

Postby christos » Mon May 22, 2017 4:22 pm

OK, new blog entry:
I got a new shifter and it works! But I've isolated the problem to overheating since I get some flickering (much less severe than the previous one) only when the case is closed. An open case alleviates the symptoms. So I need to find what causes the system to overheat. Looking forward to reading your thoughts in the comments section below ;)
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Re: MSTE screen flickering after being ran for awhile

Postby exxos » Mon May 22, 2017 4:44 pm

Odd screen issues are normally bad caps in the video circuit. I cant speak for the MSTE as never owned one, but very common on STFMs.
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Re: MSTE screen flickering after being ran for awhile

Postby siriushardware » Mon May 22, 2017 9:07 pm

christos wrote:
However, the machine never started after that. It powers on but all I get is a black screen and a buzzing sound from the monitor port. Connecting with the L&R sockets doesn't produce the buzzing.



This problem was almost certainly a Red Herring (a false fault) caused by you plugging the 13-pin monitor plug into the socket upside down. It is very easy to do accidentally and produces the symptoms you describe, especially the buzzing sound from the monitor.

As you kept on faultfinding and removed the plug at some point and put it back in again, this time the right way up, that particular fault went away.

If you have access to some 'Freezer Spray', let the unit warm up until the fault comes on, then carefully spray individual components while the unit is on / fault is present to see if cooling any of them makes the fault go away. Note: NEVER use freezer spray on the PSU unit, use only on low voltage parts of the computer.

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Re: MSTE screen flickering after being ran for awhile

Postby christos » Tue May 23, 2017 5:50 am

@exxos: yes it's possible that there might be some bad caps, if they can cause the shifter to overheat.

@siriushardware: The plug was the first thing I checked, and I've used two different cables (composite and scart) so I've plugged it in and out quite a few times. The new shifter chip made the machine run again. I don't think that you can fry a shifter by plugging the cable upside down.

About the freezing spray, that would show me indeed which component overheats, but in all likelyhood that would be the shifter. I'll try to source some spray and see if I get a different result.
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Re: MSTE screen flickering after being ran for awhile

Postby exxos » Tue May 23, 2017 7:06 am

What I mean is, if the machine acts up faster with the "lid on" then its not necessarily the shifter.
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Re: MSTE screen flickering after being ran for awhile

Postby siriushardware » Thu May 25, 2017 9:02 pm

christos wrote:
@siriushardware: The plug was the first thing I checked, and I've used two different cables (composite and scart) so I've plugged it in and out quite a few times. The new shifter chip made the machine run again. I don't think that you can fry a shifter by plugging the cable upside down.



Sorry, I should have clarified: Plugging the 13-pin monitor plug into the ST upside down will TEMPORARILY produce those symptoms you described. But actually, you can cause damage by either plugging the plug into the monitor socket upside down or unplugging it upside down while the monitor and the ST are both on. Guess how I found that out? It didn't blow the shifter but it did blow one of the 74xx gates attached to vsync or hsync, I forget which.

My advice is never to connect or disconnect things while they are powered.

...It's a pity I don't always follow my own advice.

Good luck with finding your problem. I discovered recently that Freezer spray is not very cheap, so if you don't have any already, don't buy an enormous can of it - just the smallest can you can buy will be enough to hunt for this particular problem.

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Re: MSTE screen flickering after being ran for awhile

Postby christos » Sat May 27, 2017 5:37 pm

Hmm, new issue noticed. While playing mods or any dma sounds I get a loud hiss on the speakers that doesn't appear to be happening when I play YM audio. So I suspect the issue is also affecting DMA audio. I can't remember if this was happening before I replaced the Shifter, but I suspect not. Also using audio controls from the control panel shows that treble is affecting the issue quite a lot.
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Re: MSTE screen flickering after being ran for awhile

Postby Shockwav3 » Sat May 27, 2017 6:00 pm

Sounds like a classic PSU issue to me.

Can I haz hardware?


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