Photo: robin
  1. » Forum
  2. » Tech
  3. » Tech: Early solid state
  4. » Bally 2518-32 All tones the same
(Topic ID: 255538)

Bally 2518-32 All tones the same

By Skidave

4 years ago



Topic Stats

  • 6 posts
  • 3 Pinsiders participating
  • Latest reply 4 years ago by Skidave
  • No one calls this topic a favorite

You

Linked Games

No games have been linked to this topic.

    0
    0
    0
    #1 4 years ago
    OP
     
    DBS

    Skidave

    Pinside member

    6y 63,550 1,288 9

    Working on a 2518-32 sound card. All the tones are the same pitch. When in audio test mode, everything through U2 / U1 and the 555 look proper with my logic probe. When I probe the output of U3 Pins 1, 2 and 3, the tone changes. However, the logic probe doesn't show high or low and no LED blinking for data on those pins. I'm thinking my problem is obviously between U3 and U4 (and maybe U5). Any thoughts on this. Is U4 pulling down U3 or vice versus?

    Volume, sustain and sequence of the notes are fine.

    0
    0
    0
    #2 4 years ago
     
    PIP

    Quench

    Pinside member

    8y 114K 8,039

    If the inputs (A, B, C, D, E) to the U3 PROM are changing, but the outputs (D1 - D8) are not, then suspect the PROM.

    The PROM is used to tell the U4/U5 divider chips how much to divide the master clock frequency from U1 to produce different tones.

    0
    0
    0
    #3 4 years ago
    OP
     
    DBS

    Skidave

    Pinside member

    6y 63,550 1,288 9

    I was hoping it was not the PROM. Any way to test and verify it is one or the other? If I pull U4 and my logic probe starts showing output on U3 pins 1, 2 and 3...then maybe U4 is suspect.

    0
    0
    0
    #4 4 years ago
     
    PIP

    Quench

    Pinside member

    8y 114K 8,039

    Make sure your logic probe is set on TTL to check the PROM outputs.

    It sounds like a problem with the pin 15 (chip select) of the PROM which has internally disabled it and made the outputs go "tri-state" (open circuit/floating).

    It's very unlikely for U4/U5 to make those pins go indeterminate state (floating).

    If you've got an EPROM programmer that supports PROMs you can test it.

    Otherwise if you really want to test U4/U5 in circuit, you'll have to pull out the PROM and simulate some output states by connecting the D01 - D08 U3 socket pins to either 5 volts or ground (mix it up). If you get a different tone, and mixing up the output connections again gives you another tone, then suspect the PROM.

    You could also try swapping U4 and U5 around since they are the same chip.

    0
    0
    0
    #5 4 years ago
     
    AMS

    barakandl

    nvram.weebly.com

    12y 132K 10,418

    correct rhythm but the pitch never changes is almost always bad PROM.

    0
    0
    0
    #6 4 years ago
    OP
     
    DBS

    Skidave

    Pinside member

    6y 63,550 1,288 9

    So l lifted the jumper that ties U3 pin 1 to U5 pin 2 because I wanted to see if the output of U3 was being loaded by U5. No luck. Appears no output signal from U3 pin 1 (or any others).

    U3 = Bad

    Reply

    Wanna join the discussion? Please sign in to reply to this topic.

    Hey there! Welcome to Pinside!

    Donate to Pinside

    Great to see you're enjoying Pinside! Did you know Pinside is able to run without any 3rd-party banners or ads, thanks to the support from our visitors? Please consider a donation to Pinside and get anext to your username to show for it! Or better yet, subscribe to Pinside+!

    This page was printed from https://pinside.com/pinball/forum/topic/bally-2518-32-all-tones-the-same?hl=skidave and we tried optimising it for printing. Some page elements may have been deliberately hidden.

    Scan the QR code on the left to jump to the URL this document was printed from.