Bop dmd fault

[telf]

Hi, bought a bop recently with a few issues but got it cheap. Main issue is dmd fault. It suggested to me a was the display board rather than the display it’s self. I took it to a specialist pcb repair company and after a week got a call to say there’s no fault there and it must be a fault with the pin?

Any advice with this would be much appreciated, cheers Telf

 

[carl lawrence]

Possible dry joints on the display or bad data connection !

 

[telf]

Possible dry joints on the display or bad data connection !

Cheers Carl, I have looked for dry joints but I suppose I should go over them again just in case.

 

[carl lawrence]

Where the display fixes to the board and at the male connector to board as well

 

[Jay Walker]

Hello, Telf,

I doubt that both of the display envelopes have burnt-out the same digits (No.s 5, 6 & 8, going by the picture), so my suspicion would be that they aren't being driven by the display controller. That in turn may not be receiving controls for those digits from the Cpu board, via the grey ribbon cable attached to the connector marked 'Display' - though AIR it's only used by the three designs with alpha-numeric displays, including B/o/Pinbot

According to the schematics for the similar board(s) in the contemporary game FunHouse, though, the same four lines are used to control all sixteen digit 'strobes' of each display envelope, so they must be reaching the display controller board.

Digit strobes 5 thru 8 for both of the upper envelopes share chip U 6 on the display controller, specifically the 'B' section of the two it contains ('A' is used for digits 1 thru 4). A similar arrangement for digits 8 to 16 (the r/h half of each lower envelope) uses U 7, but with section 'B' for digits 9 to 12 and 'A' for digits 13 to 16.

The same four lines (STX 1-4) are used to 'address' each section of these two chips, so there can't be a problem with the lines. The four sections are selected individually as required, and the problem may be with this, i.e. the selection for 5 to 8 not working. Selection is performed by half of chip U 11, using two of the data lines - the other half multiplexes the other two of the four data lines into the four specific digit 'STX' lines. The only stage between U 11 and the machines' full-on data lines is U 16. This splits these four lines (which are common across the board) into two pairs, one to each half of U 11.

In short, I'd suspect U 11 and/or U 16 of the display controller board, despite the existing diagnosis. Another possibility is that the high-voltage switching ('down stream' of all this, and closest to the envelopes themselves) is damaged, but that would mean that two chips, U 8 for the upper display, and U 5 for the lower, are both faulty

 

[telf]

Hello, Telf,

I doubt that both of the display envelopes have burnt-out the same digits (No.s 5, 6 & 8, going by the picture), so my suspicion would be that they aren't being driven by the display controller. That in turn may not be receiving controls for those digits from the Cpu board, via the grey ribbon cable attached to the connector marked 'Display' - though it's only used by the three designs with alpha-numeric displays, including B/o/Pinbot

According to the schematics for the similar board(s) in the contemporary game FunHouse, though, the same four lines are used to control all sixteen digit 'strobes' of each display envelope, so they must be reaching the display controller board.

Digit strobes 5 thru 8 for the upper envelopes share chip U 6 on the display controller, specifically the 'B' section of the two it contains ('A' is used for digits 1 thru 4). A similar arrangement for the lower envelope uses U 7, but with section 'A' for digits 5 to 8.

The same four lines (STX 1-4) are used to 'address' each section of these two chips, so there can't be a problem with the lines. The four sections are selected individually as required, and the problem may be with this, i.e. the selection for 5 to 8 not working. Selection is performed by half of chip U 11 - the other half gates the four data lines into the specific digit 'STX' lines. The only step between U 11 and the machines' data lines is U 16. This splits these four lines (which are common across the board) into two pairs, one pair to each half of U 11.

In short, I'd suspect U 11 and/or U 16 of the display controller board, despite the existing diagnosis

Many thanks jay I’ll look at this when I get a min.