(Topic ID: 287927)

RS NVRAM installed No DMD

By Eddie

3 years ago


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#24 3 years ago

Page errors or RAM address errors are typically issues on the DMC (dot matrix controller). The PinWiki has a small section on page errors but I think if you're going to play an odds game you have higher odds with replacing the 6264 SRAM on the DMC than any of the ICs involved with page selection.

Note: you can use a low voltage DMD to isolate issues without having to rely on a working high voltage section on the DMC.

#30 3 years ago
Quoted from Eddie:

The controller is a PinLED its all surface mount so changing out a 6264 is out.

The SRAM might be a discrete IC. Their website shows an image of the board with a DIPW-28 socket and an SOIC-28 IC. I don't know their circuitry but the SOIC-28 might be the SRAM. Otherwise the SRAM will be integrated inside the other SMT IC and ... yes ... you will not be able to change that easily if at all.

Quoted from PinballManiac40:

If it is, might be tough to repair this board.

I bet all the discrete logic ICs of the original Williams design (or equivalent circuitry) are embedded in that SMT IC. Might be an FPGA. I don't know for sure as I have no experience with this board.

A replacement is available @ https://pinballbasement.com/collections/wpc89-boards/products/wpc-dot-matrix-dmd-controller

#32 3 years ago
Quoted from Eddie:

Is there any chance there could be something on the WPCS board or are the page errors strictly DMD board related?

The CPU writes data into the SRAM on the DMC through the ribbon cable. The DMC duly displays the contents of the SRAM on the DMD.

It is not possible to be certain that a problem is isolated to one board or another without inspecting the data transfer on the ribbon cable or swapping out with a known good on one end. The problem is that the CPU could be writing bad data (the data put out on the bus through the ribbon cable) and the SRAM on the DMC is good or the CPU could be writing good data and the SRAM on the DMC is bad. Or any other combination or possibility of problem.

If I were to bet I would say the problem is on the DMC rather than the CPU. That would be an odds game based on the error you report. There is no conclusive evidence to back up my claim.

#36 3 years ago
Quoted from Eddie:

I just checked out the Pinwiki info and it seems straight forward and an easy repair if I had a WILLIAMS DMD Control board LOL

Which is why when I make a reproduction board I try hard to keep as true to the original Williams design.

  • No schematic is necessary.
  • Familiarity with circuit and components.
  • You may already have components on hand.
  • All through hole design for easy service.
Quoted from Eddie:

Is that your store the Pinball Basement?

No. Pinside user lordloss or PinballBasement is the proprietor of that store.

Quoted from Eddie:

Maybe the Pinled has settings for COLOR DMD Voltage?

It almost certainly outputs the +12V required for the ColorDMD. Some of the plasma displays require this voltage to operate correctly.

<shameless plug>I have a variety of boards that you may be interested in having around as "known good" for comparison or testing. Of particular interest to you might be the WPC-89 CPU board I have. This board supports the standard configuration and with a jumper setting, the removal of some ICs (in sockets) and the addition of a small daughter board will support WPC-S. You can reverse those changes to restore it to WPC-89 standard. An "all-in-one" solution.</shameless plug>

#41 3 years ago
Quoted from Eddie:

Is the Color DMD that I ordered one of yours?

No. I don't have anything color. The only DMDs I have are monochrome. They are ready for consumption by people who do repairs but not quite ready for public consumption. My goal is to have a low voltage (bench friendly) DMD as well a white DMD for my Twilight Zone (and perhaps other machines).

#45 3 years ago
Quoted from Eddie:

My mistake I meant DMD controller board not ColorDMD Guess I was tired.

That's understandable.

I make red boards. I only sent out a few green bench testing boards. The board you ordered is from Pinball Basement. It is a re-fabrication of the original Williams design and layout presumably with components recently manufactured. The original board is from PinLED - a company in Germany. PinLED boards have extensive use of SMT.

I have a DMC board reproduction but it does not work 100%. It mostly works but I need to figure out what's wrong with it before making it available.

#50 3 years ago
Quoted from Eddie:

... the Display images in attract mode and in test mode.
Note the Complete Chaos in the Test Patterns.

Actually ... that's not chaos. It's ordered. "(col - 1) % 8 = 5" is fixed (either on or off). That provides much stronger evidence that it is a logic problem in the processing of the SRAM than a logic problem in the display itself.

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