(Topic ID: 177164)

[SOLVED!] Sega White Star (SST) - display issue


By OHMI_Arcade

2 years ago



Topic Stats

  • 34 posts
  • 6 Pinsiders participating
  • Latest reply 2 years ago by PinballManiac40
  • Topic is favorited by 2 Pinsiders

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#1 2 years ago

My SST's display tests perfectly in test mode and displays 99.9% of all graphics correctly. However, I've noticed that the Brain Bug stepper motor test screen and the Live Assault multi ball screen don't appear to display correctly (please see pics). Any ideas why these (2) screens would be incomplete when all others seem to appear fine? I'm not too clear on how the images are called by the CPU. Thanks! - Tim

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#2 2 years ago

Update: I read that the long ribbon cable often goes bad so I did the recommended test of flipping the cable connectors (on both end of the cable). This resulted in a completely black screen. If the cable was good it shouldn't change anything since a wire is a wire. I've ordered a new cable. Hopefully that cures it.

#3 2 years ago

I'm interested to know what the outcome is. I have similar issues with the dmd during jackpots during live fire assault multiball and during planet nukes. whenever the screen makes explosions it comes out black like above.

#4 2 years ago

Tried the new cable... made no difference. Hmmm....

#5 2 years ago
Quoted from OHMI_Arcade:

Tried the new cable... made no difference. Hmmm....

Just to check. Do you have the ribbon cable red stripe pin one each end ?

LTG : )

#6 2 years ago
Quoted from LTG:

Just to check. Do you have the ribbon cable red stripe pin one each end ?
LTG : )

Yep, I even checked continuity on pin 1s... to double check everything was right. I'm really at a loss on this one. I'd hate to just start replacing boards (since I don't have any spare boards for this system). The boards themselves look quite clean.

#7 2 years ago

Have you tested the display high voltages?
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#8 2 years ago
Quoted from ChrisHibler:

Have you tested the display high voltages?
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info

At the dot matrix display board I have -92VDC where I should have -98VDC and -113VDC where I should have -110VDC. Do you think these are outside of normal ranges? Thanks.

#9 2 years ago

That's a bigger gap than the 12V spec but I've seen that before with no ill affects.
What about the nominal 68VDC at the other end of that connector. That's another important one.
--
Chris Hibler - CARGPB #31
http://ChrisHiblerPinball.com/contact/
http://www.PinWiki.com - The new place for pinball repair info

#10 2 years ago

I've got 67.4VDC on the 68VDC pin.

#11 2 years ago

That's good. I'm not thinking that the problem is caused by power even though the spec 12VDC gap between the negative voltages is bigger.

Having said that...I have no idea what is going on there.
It only happens during those two tests, right?
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#12 2 years ago

Thanks Chris, as far as I can tell it only incorrectly displays these screens. I truly appreciate the guidance you provided. There is a section on the display board that looks like there's been some trauma but maybe its normal. Unfortunately this is my first and only Sega so I'm not sure what is "normal". I'm going to try replacing the display rom... maybe it got jumbled somehow. Really not sure where else to look next. thanks. df7bdb4a98c5020195c50fd5a4748b6e04f92508 (resized).jpg

#13 2 years ago

I don't know that either that board damage or a new ROM will help the situation. But I'm very interested in finding the resolution.
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info

2 weeks later
#14 2 years ago

Update: I got a new display rom and swapped it in. The screen did nothing... no images at all. I went back to the original rom and still nothing. I looked at the socket and it looked iffy so I replaced it. Tried it out tonight. Still no images at all. So... by messing with the board I assume something that was close to failing failed. I now need to determine if its the actual display or the control board. I would assume it's the board but I'd like to figure out a way to test the display before I spend $200+ on a new control board. Frankly, I'm in a little over my head on displays. Time to google.

#15 2 years ago

If you want to send that board to me, I'll be happy to test. it.
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#16 2 years ago

I appreciate the offer Chris and I may take you up on it. One thing I noticed is that the enable display signal is not being output from the display controller board. I'll probably try tracing this back on the bench to see if I can make anything happen.

#17 2 years ago

Update: I bought a new RottenDog display board since I really want to get this SST finished and trade it out. So, as of now I have replaced the display board, the two ribbon cables, and the display ROM. Once again everything works EXCEPT the Brain Bug stepper motor test screen and the Live Assault multi-ball screen! So, I'm back to where I started. Once again, the display test shows all pixels working. This points me to the MPU board?

#18 2 years ago

I did the DMM test on the 74HCT273 at U201 on the CPU board (which buffers the display data) and got a few odd readings. Unfortunately that chip isn't socketed so its going to take a bit longer to swap it out and see if that's it... plus I need to order a 74HCT273. Stay tuned.

3 weeks later
#19 2 years ago

I now have a new, socketed U201 but unfortunately the display problem continues. The MPU board looks super clean.

To recap I've:
1. replaced the ribbon cable from MPU to display board
2. replaced the display board with brand new one
3. replaced ribbon cable from display board to display
4. replaced display ROM
5. replaced display buffer U201 on MPU board
6. reflowed the display connector pins on the MPU board
7. checked display voltages

This has me really stumped... does anyone have any idea what to do next?

I'd appreciate any ideas at this point.

thanks
Tim

#20 2 years ago

I would test the Getaway DMD display in SST. You can hold the DMD on the outer edges of the board so you don't get shocked and so you don't have to go through a lot to swap the DMD just to see the results. The SST DMD display has a lot of dark pixels, which I think would take more voltage for them to turn on and even looks like screen burn in from the same text being displayed over and over. So I feel it may be on its way out. It would be even interesting to see how the DMD display does in Getaway.

#21 2 years ago

Maybe try the u216 rom chip
I believe this is tied in with the video section of CPU board

#22 2 years ago

Turns out it is the DMD. Even though everything looks good in the DMD test it must not be able to illuminate all pixels fast enough for rapidly changing text. Thank you chrishibler , pinballmaniac40 , ltg , and stretch7 . The help you gave is very appreciated!
Tim

#23 2 years ago

The pixels are dark, so they are essentially burning out, at least in the middle part of the display.

FYI. A ColorDMD has been made for the Getaway, if you care about that at all. Though, they are currently out of stock. http://shop.colordmd.com/colordmd-replacement-display-for-the-getaway-high-speed-ii-pinball-machine/

#24 2 years ago

The pixels look bright during the DMD test... that's so odd. I'm pretty new to DMDs.. I guess I've learned never to trust the built in test. Thanks again!

#25 2 years ago
Quoted from OHMI_Arcade:

The pixels look bright during the DMD test... that's so odd. I'm pretty new to DMDs.. I guess I've learned never to trust the built in test. Thanks again!

The quality of the display is very much dependent on what is being displayed. Some display images work, and some don't, and the logic seems counter intuitive as to which ones work and which ones don't.
--
Chris Hibler - CARGPB #31
http://ChrisHiblerPinball.com/contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#26 2 years ago

Can you snap a picture of the DMD in the display test? All the pixels during this test should all be at the same brightness. I suspect they are not.

Also, I would like to see a picture of the DMD with no power to the DMD.

#27 2 years ago

The DMD is presently mounted in the machine and there is too much reflection to get a good photo when off... here is a pic of the DMD during test mode:

dmd (resized).PNG

#28 2 years ago

That is a shocker. Can you snap a picture of the back of the DMD? Interested in seeing the brand and the actual board layout.

#29 2 years ago

I'll take pics of the back when I swap out the DMD. I know it had a Cherry sticker on it.

#30 2 years ago

Did you find a used DMD?

#31 2 years ago

I'm going to put my getaway display in it and then decide whether to get a color DMD for the getaway. That's the plan anyway.

: )

#32 2 years ago

Would be interesting to know how the SST DMD works during Getaway's gameplay.

#33 2 years ago

Here's a pic of the back of the old DMD. I tried it in my HS2 and it works except for displaying text that is only 1 pixel wide (see pic).

IMG_3588 (resized).JPG

IMG_3587 (resized).JPG

#34 2 years ago
Quoted from OHMI_Arcade:

I'm going to put my getaway display in it and then decide whether to get a color DMD for the getaway. That's the plan anyway.
: )

That is a very good plan for Getaway. The LED ColorDMD will be a nice fit into SST in the future. Sigma display works now and you can even choose the single color you want the display to be. No doubt this game will be colored at some point.

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