BayWatch DMD not working - TECHS

Just bought a BayWatch with a Non-working DMD. Why, you ask. Cos it was ½ price of others. And I feel WE can fix it. Ya Pinside TECHS!

The guy said that it worked before it went in to storage, but not when it came out. He also said that he put this DMD in to MSF (Frankenstein) and it worked. I think this is all true, but who really knows.

So what I found so far – the 8 amp SB fuse on rectifier 3 was blown. This rectifier supplies power to the DMD. I only had 7.5 amp SB Fuse to replace it with and yes it went too, slowly, LOL.

If I remove the power cable from the DMD and replace the fuse it does not blow.

I have also looked over the DMD PCB for obvious faults, EG popped caps. Look fine

The DMD is a Cherry.

Anyone got ideas, thanks?

PS - the rest of the machine is 100% working.

help-485.jpg

#2 9 years ago

BAD

Brtlkat

Pinside member

Fort Pierce, FL

11y 52,050 1,511 14

Could be a bad BR or you need a new dmd. Test the BR with a meter.

#3 9 years ago

MAR

Mrjamma

Pinside member

Gate City, VA

11y 39,650 524 26

If that display worked in Frankenstein, then it is not shorted so the likely suspect is bridge rectifier BR3. Replace it and you will have a Happy Pin!

#4 9 years ago

HWK

Hawk007

Pinside member

11y 63,400 1,618

check voltages and then dig deeper. [post here]

#5 9 years ago

Chrisbee

Pinside member

I have changed the BR, not fixed my problem, Darn!!!!!

#6 9 years ago

???

lostlumberjacks

Pinside member

Evart, MI

11y 48,900 688

Here's one for you to try, if your getting proper voltage, replace the ribbon cable. Had this with a Frankenstein. No picture then put a new cable in and voila!

#7 9 years ago

HWK

Hawk007

Pinside member

11y 63,400 1,618

Please check your voltages at the dmd with your game on and see what they are...Without knowing that it is hard to help. And cables/connectors are a known weak link in these and all games...reseat several times and look for any damage

#8 9 years ago

Chrisbee

Pinside member

Quoted from Hawk007:
Please check your voltages at the dmd with your game on and see what they are

I can't, the fuse blows. So somewhere I have a short. When I measure the resistance across the 18V supply terminals on the DMD I get 70 ohms, so i'm a bit surprised that when the DMD is powered up the fuse blows (see above schematic).

So right now, I have changed the BR (#3), and it reads 19v no load. When I meter the board at the 18v terminals, I see zero first up then it climbs to 70 ohms over a few seconds, I'm assuming this is the 3 x 4700 uF caps charging.

If I leave the DMD power supply cable off, the fuse stays intact, so it appears there is no short from the BR to the DMD.

I emailed the guy who had the machine before me, (the DMD was not working then) this is his response

"Hi Chris,

When we swapped the unit over it was a complete swap. We just disconnected the cables and did a complete swap including boards.

We didn't blow any fuses, so that is news to me.
Which fuse?

The multimeter readings were a volt or two out so we assumed it was a voltage issue to the DMD, but these readings were showing an under-voltage not an over-voltage."

OP
Quoted from Chrisbee:
The guy said that it worked before it went in to storage, but not when it came out. He also said that he put this DMD in to MSF (Frankenstein) and it worked. I think this is all true, but who really knows.

Hawk007, thanks for taking the time.

#9 9 years ago

ROB

videorob

Inactive member

How long was it in storage...Just guessing here but long term storage and then moving a game.... Could something have dry rotted and then broke/come loose causing a short? Any obvious broken wires, traces, connectors etc.....?

#10 9 years ago

Chrisbee

Pinside member

Quoted from videorob:
How long was it in storage

Not sure, but i have looked for rubbish, ETC. The board is fairly clean.
The hardiest thing about the DMD board, if the DMD is covering the back of component, making it hard to work with! And the fun continues.

#11 9 years ago

ROB

videorob

Inactive member

Yeah, gotta love those HUGE displays. I treat Maverick with kid gloves because of that.

Wish I could help more. Normally I'd call ribbon cable bad but you're getting an instant blown fuse....hmmmm transistor? I don't have a manual or complete recall of schematics like a lot of guys "seem" to have...lol

#12 9 years ago

Chrisbee

Pinside member

Can someone, take a pic of the back of there DMD board, just to make sure I have got it cabled correctly, please.

#13 9 years ago

ROB

videorob

Inactive member

Give me a few....I'll see if I can get a decent pic or 2 tonight......It's Maverick not Baywatch but that shouldn't matter.

#14 9 years ago

ROB

videorob

Inactive member

Hope these will help. My back is toast so I couldn't pull the machine out all the way.

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#15 9 years ago

ACE

Acejedi

Pinside member

Citrus Heights, CA

11y 51,900 459 57 15

I hope you get your problem fixed, This is the exact reason why Baywatch and Batman no longer reside in my collection, the Big DMD always scared me that it would fail and be so expensive to replace. Hopefully someone here will be able to help you get it fixed.

Joe(acejedi)

#16 9 years ago

ROB

videorob

Inactive member

Quoted from Acejedi:
I hope you get your problem fixed, This is the exact reason why Baywatch and Batman no longer reside in my collection, the Big DMD always scared me that it would fail and be so expensive to replace. Hopefully someone here will be able to help you get it fixed.
Joe(acejedi)

They don't really scare me into not owning. If they do develop a problem, it's not always the DMD.

#17 9 years ago

ROB

videorob

Inactive member

OP, I'll try to get better pics tomorrow if you need them. Just point me to what you need taken.

_{Post edited by videorob: typical typing faster than my brain}

#18 9 years ago

ACE

Acejedi

Pinside member

Citrus Heights, CA

11y 51,900 459 57 15

Yeah some people love them for me its just to expensive to replace if and when they do fail.

Joe(acejedi)

#19 9 years ago

HWK

Hawk007

Pinside member

11y 63,400 1,618

It sounds like a bad cap. Replace the c1 and any caps 'in line' in the circuit especially those in line of the power...they can bring the whole circuit down. I had that on a wpc sound board..tantalum cap shorted and caused weirdness..

#20 9 years ago

ROB

videorob

Inactive member

To touch back on my original question...."how long in storage" and then moving from A to B to C and then D.... because with age, the large DMD may "blank out", or cause the game to reset intermittently. The dot matrix display controller board has its own 68000 micro processor, which runs at 12 mHz.

It operates best with logic +5 volts right at 5.0 volts! Any drop in voltage (to even 4.9 volts) can cause the display CPU to shut down or reset. The same goes for a short or spike in voltage causing the fuse to blow. As these games get older, the connectors fatique, and small amounts of resistance appear. Or the grounding strap going to the display board can become loose. These problems can cause the +5 volts fed to the display to drop or rise enough to cause problems. It seems funny that the seller was indicating a low power problem but you seem to be getting to much power or a short somewhere. A bad cap can certainly be a problem...again age, condition/length of storage, etc...

Take some readings from the connector (disconnected from the DMD) so the fuse doesn't blow and report back.

#21 9 years ago

Chrisbee

Pinside member

Quoted from videorob:
Hope these will help

Thanks so much for doing that.
The good news is it is the same
And the bad news its the same.

Thanks for your help everyone. I'm away for a bit so I will need to let this problem go, for now.

#22 9 years ago

TAK

ThatsaKicker

Inactive member

Old Colwyn

10y 41,650 354 1

Quoted from Acejedi:
Yeah some people love them for me its just to expensive to replace if and when they do fail.
Joe(acejedi)

Sorry to hijack the thread but if you needed a Sega display nowadays and don't mind led, I believe the DMD Extender from Dr pinball in the UK can be used for a replacement

#23 9 years ago

Chrisbee

Pinside member

http://pinside.com/pinball/forum/topic/diy-addams-family-poor-mans-color-dmd

Quoted from ThatsaKicker:
I believe the DMD Extender from Dr pinball in the UK can be used for a replacement

It may come down to something like this, thanks.

And good morning to you, ThatsaKicker!!

#24 9 years ago

ABC

Crash

Pinside member

12y 141K 14,128

OP
Quoted from Chrisbee:
It may come down to something like this, thanks.
And good morning to you, ThatsaKicker!!

See my thread if you're going this route. In my opinion it's a no brainer.

1 month later

#25 9 years ago

Chrisbee

Pinside member

https://pinside.com/pinball/forum/topic/diy-addams-family-poor-mans-color-dmd/page/6#post-1842244

Finally got back to my DMD issue.

Thought to add a bit of info, for future repairs for others.

First did a bit of checking, looks like Q11 was Tip fodder. Q11 oscillates via input to the gate from U20 (30kHz). As stated in other threads, it’s hard to get to the underside of the PCB. So I decided to cut the 3 legs of the old Q11 and solder the new part to the existing legs.

Got the old Q11 out, and sure enough it is shorted between pins 2 and 3. 0Ω and way and 40Ω the other, expect the internal diode is at fault.

Got the new Q11 and installed. Feeling confident, plugged all back in and powered up… fuse blows.

Discount the drain on Q11 and metered the transformer , from any pin to any other pin 0Ω.

My guess, Q11 has failed and allowed the transformer to overheat just enough to make the insulation on all six winding connect, bugger!

Thought about a rewrap, but what a job just to get the thing off the board.

That’s the bad news, now the good news – Let’s try out a new LCD colour conversion.

Crash I’m currently reading your thread.
https://pinside.com/pinball/forum/topic/diy-addams-family-poor-mans-color-dmd/page/3

and just download DoctorPinball’s PDF
http://www.drpinball.co.uk/docs/ApplicationNote1.pdf

Looks like you guys are going to make this easy for me, thanks in advance.
So I’m going to change a DMD to LCD on my Baywatch, is there any advice specific to this machine that may help?

#26 9 years ago

ABC

Crash

Pinside member

12y 141K 14,128

All I would suggest is follow the parts links on the opening post on the first page (obviously you want to hit the jump link to take you to the Sega conversion post). Those should work for you. Also, after setting it up be sure to set the mode in the software on the SD card to Sega jumbo. Otherwise it defaults to Bally/Williams and you will get this:

2 months later

#27 9 years ago

Chrisbee

Pinside member