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SEGA DMD dead?

So I’ve ordered a new meter (looks like a Fluke copy) which will be here tomorrow, so I can test the crystal - any tips on which of the four pins to check would be appreciated. I’m
Guessing I need to power the board up and then check I’m getting the correct 24.0000 hz from the output to the red probe, with the black going to gnd?

I can’t see from the schematic in the manual what pin does what, so it’s gonna take some trial and error.

I’m also unable to find anything I can confirm is a like for like replacement although I found these online so am hoping:

1. This is a suitable replacement
2. It will therefore have the same pin configuration to help me test...

It seems to have the same dimensions, it’s 5v (+/- 10%) and frequency of 24.0000hz

https://m.reichelt.com/gb/en/?LANGU...MIzuWKyYS61wIVKijTCh03WgluEAkYASABEgKYIfD_BwE

If these are the right ones,
I might buy some extras and give them @pinballmania to put on the website in case others are in the same boat as me.


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Look at the datasheet for the component that you posted. I would say to test, DMM set to Hz, black lead to pin 7 and red lead to pin 8.
 
chris b said:
Why not just take to Andy’s and test if the display has gassed out your just wasting money and time swapping components ****ing in the wind is the correct term I thing
Click to expand...

That’s the plan Chris and I’ve booked the time off to do it.

But a round trip to Andy is 3-4 hours in a car and £40-50in fuel. IF there’s a fault with the crystal, it will cost no money and way less time to find out that way.

The capacitor was a waste of 15 mins and 90 pence though.

Of course an excuse to go and meet Andy and talk Pinball with him for an hour is the silver lining in the cloud that my DMD has become! ;)
 
Just for the benefit of anyone following this thread in future, Andy suggested I check for activity on pin E of the cpu, rather than the crystal. I’ve found the schematic - page 86 shows the pin in relation to the cut corner, enabling you to identify the correct place to test...

uploads.tapatalk_cdn.com_20171113_7a1af6051bbca01dcd2ab2e555d0a1d1.jpg

The probes I have make it easy to test from the top of the board using the pins down the left hand side (above).

uploads.tapatalk_cdn.com_20171113_d78e677290670df474cfd471cad65e07.jpg

https://4donline.ihs.com/images/Vip...-13.pdf?hkey=EF798316E3902B6ED9A73243A3159BB0


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A rock solid 1.199mhz between CPU Pin 22 (marked E) and CPU Pin 16 or 17 (both marked GND).

Hopefully I’ve tested that correctly...

I guess this is telling me the CPU clock is working fine, which means the crystal is working and therefore the screen is probably dead. But the good news is I’ll get to meet Andy tomorrow and find out for sure [emoji4]


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Hi Dom, is there a standard ‘orange’ mode? If so is it possible to post a photo of it close up? The cost of your unit and a direct replacement are almost identical so I’m really struggling to decide which way to go with it.

Thanks,

Ed


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Dammit. Local TV man can’t help. Worth a try.


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I will try to photograph it for you. It’s somewhat close to the original but since both techniques are different you never will get the same result.

... i would buy an original at the same price IF it was available, but it isn’t unfortunately. That has been the main reason to build this replacement system ;)

Dom
 
I may have one a spare one kicking around, but won't be able to get to it for maybe a week or more. Pretty sure it worked last time it was tested but of course would check it out to make sure it's all working. If interested, send me a PM.

Did you manage to test your display at Andy's?
 
Thanks G-501 I will PM you.

I did manage to confirm the display driver works on Andys screen and that mine my screen is probably the issue. Have since soldered fly leads to the spare pads at J4 on my driver board to isolate my power supply. Was getting 4.94v at the ends before soldering to the board so that’s my PSU out too.

So has to be the screen. I’ve got a friend of a friend who is going to look at the display board for me next week as a final stand. After that I’m giving up.
 
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Just bumping this thread again as I’ll be looking to get a new DMD in the next couple of weeks.

Had a guy look at it but he needs to test it on the machine now so that’s the last straw and I’m not very hopeful so am planning to get a new screen in the next fortnight.

Cheers guys,

Ed


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So the saga continues. Had a guy come over with an oscilloscope today and probe the board with the game running.

For anyone interested or with a cherry display, he found a defective transistor (Q5) which shorts to a pin on one of the chips.

He’s taken it away to:

1. Replace the transistor and see if it blows again

2. If it blows, swap the chip out

I’m not going to attempt to do this myself as the chip pins are so small and close together you need to be able to heat it to just the right temperature and lift it to avoid ripping the tracks off.

If this fixes it, it could be handy for anyone with a dud cherry dmd lying around to see if they can get it working again.

I’ll keep this thread updated.


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Great news, especially for anyone with a dud sega dmd made by cherry that just randomly packed up one day... you might want to replace Q5 (a transistor, circled) on the display board itself:

uploads.tapatalk_cdn.com_20180126_e27daaff706b49e5b50a8c7b0a19e690.jpg

uploads.tapatalk_cdn.com_20180126_2cf1153c152b053b9ede41e5a7d71376.jpg

The original was a small surface mount block type. This new one is just one the guy had lying around but probably rated better so less chance of going pop again.

Ignore those red caps - I put those updated ones on while trying to fix it.

Anyway, super stoked and hope anyone reading this with a dead screen manages to get theirs working [emoji106]
 
hi, got a batman forever, dmd probs too....did it also knock out your sound?
 
Sgt GrizZ said:
Flaky voltage from the power board will cause dmd and soundboard grief - measure voltages , check connectors
Click to expand...
on the controller back, im getting 4.9, on dmd 4.94 and 18.55. the game has no sound. but can play game as normal! sometimes have to wait a bit on just gi then pull door switch that isolates main power to coils. the 6800 chip gets very hot. apart from dmd and sound...it all works. had a video call with phil, ph, and even bob popped in with some boards, all confused! lol. I also get a quick flash of noise on dmd when power up and power down. this all started when i had machine on, was adjusting the sound...then saw the dmd going all weird, so did reboot, now this! thanks for any help.
 
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update....so brought a rotton dog psu, the one for sega large dmd displays. £171 with 24hr delivery. still no sound but the display now has some funky single lines going across then disappear, still no display. if door closed...no gi lights or any thing....open the door...gi comes on. power off the door open...power on gi lights on then after a moment the playfield lights go in to attract mode, then closed door, and i can play machine as normal but no sound or display.
 
Very strange fault Grasping at straws but I would try to better isolate where fault may be.

E.g. disconnect cn3 on the sound board so that volume potentiometer is no longer connected and see If any change.

If no change disconnect cn2 on sound board to see if display works without sound

Then reconnect cn2 on sound board and disconnect dmd at both connectors and see if sound works without display.
 
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