Help:DE/Sega/Whitestar DMD Controller Board+Rottendog DPS004 TFTC

Is it a Babcock display? What does pin 7 measure in your WPT? Have you tried the WPT display with the Rottendog? While you wouldn't think 11.7v would be a problem, for an older Babcock, it might.

viperrwk

#3 10 years ago

MAT

snyper2099

It is a Cherry display. I have 2 other good tested displays, both of which are Cherry's, and neither work in the TFTC.

#4 10 years ago

CMX

viperrwk

Inactive member

http://pinside.com/pinball/forum/topic/new-rottendog-ps-for-dequestion?ti=0

You may have a bigger problem then...

viperrwk

#5 10 years ago

MAT

snyper2099

I don't think that thread is relevant, even though I'm using Cherry displays... All the voltages pushing out to the DMD itself are in good ranges(given above). Also, the Cherry displays both tested good in my WPT after testing them in my TFTC for an extended period of time.

I'm still looking for some advice regarding the probing of components on the DMD controller board. Can't really find many resources on the web about fixing that specific DE/SEGA board... I only seem to see DE power supply fixes regarding DMD failure.

#6 10 years ago

CMX

viperrwk

Inactive member

Pin 37 on the 68B09 is the reset line. If this line is low, the CPU is held in reset. It must go high for the board to start booting. The reset pulse comes from the CPU through pin 20 on CN3 to U15 and then U1. You can manually reset the board by shorting the reset pads next to CN3.

My best guess - if the line is always low I would suspect U15. If not, given what you've already done and described, it's probably the PAL.

viperrwk

_{Post edited by viperrwk : forgot about U1 in the circuit}

#7 10 years ago

MAT

snyper2099

Still confused about that MPU reset pulse. The display controller board SHOULD come on and display the ROM info, even if the MPU is not installed in the game. I know that because when the game did not have an MPU in it (a month ago) and I powered it on, the DMD came on and displayed this info.

Pin 37 on the 68B09 reads 4.99VDC when I tested it just now. I guess one PAL chip or both are likely bad? Do those 2 PAL chips all contain the same code on every game that uses them?

#8 10 years ago

CMX

viperrwk

Inactive member

Here's how I believe it works. If someone who knows for sure can chime in that would be great.

You're right - when you turn the game on the board initially boots because it shows the ROM info. The reset line is held low by U1 long enough to let the rest of the board stabilize and then boot. But exactly what to display has to be sent over from the main CPU. So the main CPU has to send a reset pulse to restart the display controller and start receiving data. This pulse comes over pin 20 on CN3, through one NAND gate on U15, the other side of which is tied to 5v. Two highs output a low which goes to a second gate on U15. The other half of that gate is tied to the reset pads on the display controller board which is normally high. This second low/high combination outputs a high which then is inverted by U1 to a low to reset the CPU.

Since you have a logic high on the reset line, that circuit appears to be working and therefore U1 and U15 are probably fine. You know U15 is ok if you get 5v on pins 13, 11, 1 & 2 and 0v on pins 12 & 3. And we know U1 is ok because you're getting 5v on pin 37. You can try shorting the reset pads on the display controller and look at pin 37 on the CPU to make sure it goes low when you do.

Since you've put in new memory, CPU, EPROM, new cables (though resetting manually will confirm it's not a cable problem) checked the voltages and filter cap, all that's left is some of the other 74xx logic on the controller (which you can check with your meter.)

I have a DE 520-5055-01 board and a Sega 520-5055-00 board and they both have orange dot PALs at U2 and U16. These schematics from Stern also show that the PALs are orange dot - http://www.sternpinball.com/downloads/Display_Controller_Bd.pdf - so I believe the PALs did not change.

Having said all that, I just find it odd that you are having this problem after having switched to the Rottendog board. You don't hear of too many of these display controllers having the PALs fail. I'm not even sure where you can buy them.

viperrwk

#9 10 years ago

MAT

snyper2099

Just a follow-up. I borrowed a new Rottendog DMD controller board and it has fixed the issue. I have used it to test all my parts and I still have no clue why the original just "gave up" on me. Seems crazy. I tested all 3 displays using the new DMD board and they all work perfectly in TFTC.

Thanks to viperrwk for explaining the DMD board operation. Maybe some rainy day I will try to program some PAL chips and get it working.

#10 10 years ago

CMX

viperrwk

Inactive member