Monitor Problems WMS 400 Dot

[rjpohl]

WMS 400


after initial start (monitor working) then goes to DOT FAIL 0


I had a spare monitor and board that I think are good but didn't help.  I'm guessing the power supply in top box? ?


thanks for your help
Bob

[Slotman]

My bet would be top box power supply.I have replaced them with off the shelf Meanwell power supplies 12V (cant remember if there was a 5v tap or not) its been a while.

[Trisail]

I just got a WMS Dotmation and learned a bit.

I would definitely replace the caps on both power supplies and the PDU board below the lower supply. If you need caps I have them. And I am repairing power supplies for many members if you need help with them.

Got mine and it would not power up. Replaced the caps on both power supplies and it worked. Played games, everything worked.

Had some dot fails and the lamps in the door/front panel were 'flickering' dimming. The machine refused to power up out of the blue, replaced the caps in the PDU board under the lower supply and that took care of power up and the dot fails and lamp problem. Needless to say I will be doing the PDU each time with the supplies. 

Tony

[playklax01]

I would just like to add to check the serial comm cable from the dotmation board to the backplane.  If that isn't attached correctly, the CPU has no way to 'talk' to it and would also result in a Dot Fail situation.  There's 2 ports on the dotmation board that it can attach to.  If it is attached already, try the other port, either would work.

[rjpohl]

Slot has an after market PS that has harness going to backplane and main power supply.  When plugged in all 5 red lights are on on the cpu board.  When it's unplugged the middle 3 red lights go off.  I believe my problem would be in the main power supply. 

[Trisail]

So the +12V, -12V and +5V go out when you unplug the after market supply. OK, sounds good, the +5VI and the +18V LED's ( the outer 2 ) on the top board are generated from the PDU board under where the original lower power supply would be, so they would stay lit.

The dotmation display and control board would still be powered by a supply up in the top box, OR the after market supply is also suppling the voltage up to the top box for the dotmation stuff. That's OK if it is wired like that, it can be done.

If the comm cables are good, as suggested from above by PLAYKLAX01, I would still suspect the problem is with the power supply(s). Even though the LED's come on, that does not mean the voltage is 'correct'. Meaning - you need to check the ripple AC on the DC voltage. The AC voltage reading should be below 10mV, to maybe as high as 20mV might be OK. ( on a digital meter it would be .010 V ) Anything higher would mean the capacitors are bad, usually when new capacitors are installed the AC ripple would be pretty low, < 5mV. As the capacitors go bad the AC ripple goes up. This is basically noise on the DC voltage. When you are talking about suppling DC voltage to computer chips and communication chips, this ripple/noise can look like signals to these devices. Thus causing intermittent problems or just plain won't work.

You suggest your problem may be in the main power supply. If you mean the PDU board, as I mentioned before, then change the 5 capacitors on that. I fixed my machine not powering up by replacing those. They are just as important as the power supply capacitors, maybe more so as the +5VI is for the I/O board devices. It is used for the communication devices.
Tony

[rjpohl]

I replaced the upper power supply and I still get the Dot Fail.  I don't see any change at all after replacing upper power supply.  I checked the cable running from motherboard to upper display board and it appears to be good, was plugged in.  The upper board has 2 connections and I tried them both.  I've plugged the 2 CPU boards (under reels) out and re-seated them a few times.  I've tried a 2nd (known good) video board in upper box, no change.


The monitor does come on when first powered up with but goes out out with the dot fail error.  I get the dot fail error with monitor connected and disconnected from board.


Thanks
Bob

[playklax01]

Does the display show the Roms loading, or do you just get the Williams screen?  Normally it would display loading PROM1, loading PROM2.  If that's not happening, I'd look towards the Dotmation controller board in the top box.

[rjpohl]

replaced the 5 smaller compactors on PDU board per Trisail's post.  Monitor now works and game is playing.  Now the problem is the poor quality of the monitor (would recapping this one help).  I have a 2nd monitor that has much better graphics but has a few dead rows.
thanks
Bob   

[Trisail]

From what I saw on the dotmation 'monitor' there is not a whole lot you could replace without doing a lot of work desoldering. I would not recommend doing that, I didn't want to even try. I cannot look at one again for at least a week. I don't remember seeing any adjustment potentiometers. I think you might be toast on that one. Maybe someone knows more.
Tony