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(Topic ID: 270486)

Twilight Zone Pre-DCS Sound Sounding Tinny - RESOLVED


By mbelofsky

4 months ago



Topic Stats

  • 7 posts
  • 4 Pinsiders participating
  • Latest reply 4 months ago by mbelofsky
  • Topic is favorited by 1 Pinsider

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IMG_6255 (resized).jpeg

#1 4 months ago

On a TZ, after a few minutes of playing, the sounds with voice started getting garbled as shown in the first video. Sounds 14 - 21 have voice. But only 15 to 21 are garbled. Maybe this implied that the second ROM chip was bad. I sent the board for repair so it could be bench tested to ensure it would work. The repair person replaced all 3 ROM chips and changed out some capacitors.

The repair person tested the board for 10 hours using an MPU board I also sent for repair. He tested for 10 hours in test mode and it worked fine.

I received the board and tested in test mode for an hour and it worked fine.

The next day I went to play a game. As the last ball drained, I heard a pop sound and the sound became tinney as shown on the video below.

I ensured all chips are seated correctly. I ensured all ribbon cables and other connectors were in place. I replaced the ribbon cable between the MPU, Fliptronics, Sound, and display. I took each speaker out of the circuit one at a time. I removed the ribbon cable from the fliptronics board. I moved the ribbon cable from the display. I put the ribbon cable back and removed power to the fliptronics and then power to the display. I was using a different MPU so I put in the one that I sent in for repair so I was using the same MPU as he did.

The repair person is supposed to send another board to do a sanity check,

I did buy new Flipper Fidelity speakers but assume they will not make a difference until I solve the problem.

I have viewed all other Pre-DCS sound issues on pinside, I looked at the pinwiki and Clay's guides. I am not sure what to try next.

#2 4 months ago

Sounds like a speaker is blown, or maybe the cutoff cap might be bad on the tweeter. This is with the new speakers installed or still the originals?

It could be the amp - amps usually need + and - DC voltage, it sounds like it's losing the - I had that happen with a game and it turns out the -20v was missing.

See if the amplifier is excessively hot.

#3 4 months ago
Quoted from slochar:

Sounds like a speaker is blown, or maybe the cutoff cap might be bad on the tweeter. This is with the new speakers installed or still the originals?
It could be the amp - amps usually need + and - DC voltage, it sounds like it's losing the - I had that happen with a game and it turns out the -20v was missing.
See if the amplifier is excessively hot.

Thanks. I have not replaced the speakers. But I could try it later today. I didn't check the cap on the tweeter (I assume this is the smaller speaker on the right side). I did remove the wire to each speaker and that did not help.

I did check the voltages coming in and they looked ok.

The LM1875 (amp) at U1 is not very very hot.

--

Also, if a speaker was blown, why would it work in test mode for an hour one day and during the game until draining at the very end? I would assume it would have had sound issues from the moment I placed the board into the game?

1 week later
#4 4 months ago

There are not many posts that actually provide a resolution to any sound problem. I finally figured out the problem. Thanks to Joe at CST and Mike at Flipper Fidelity.

Joe was nice to send me a second board to test. The board sounded much better but was intermittent on every sound in sound test.

I bought a Flipper Fidelity Pre-DCS system to test if it were the speakers. I held off installing until I determined it was not the board.

As I was following the instructions to remove the back box speakers, I removed the small right speaker. I then was removing the wire that goes across the display and it was stuck under the display at the left side.

As part of the repairs, I replaced the DMD with a ColorDMD LCD. I obviously got the wire wedged in under the Color DMD when I replaced it. The picture below shows the flat spot of the wire where the wire was actually exposed through the insulation.

I covered the insulation with electrical tape and put back the right speaker and the connector and the single wire.

It has been testing great for the past 30 minutes.

I will still install the speakers, but another example of a self-inflicted wound.

IMG_6255 (resized).jpeg

#5 4 months ago

Thanks for posting the resolution. These are the kind of problems that drive board techs crazy.


Chris Hibler - CARGPB #31
Http://chrishiblerpinball.com/contact
http://www.PinWiki.com/ - The new place for pinball repair info

#6 4 months ago

That can happen easily, I always route my speaker cables carefully around the colordmds. They can easily slip underneath if you don’t watch what you are doing.
Glad you fixed it.

#7 4 months ago
Quoted from Lostcause:

That can happen easily, I always route my speaker cables carefully around the colordmds. They can easily slip underneath if you don’t watch what you are doing.
Glad you fixed it.

Yes. I will never do that again. I change to color dmd all the time and will now ensure all wires are out of the way. Thanks!

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