(Topic ID: 186081)

System 11a sound troubleshooting - No sound, only hum

By Robotworkshop

6 years ago



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#1 6 years ago

I picked up a spare System 11a board for my Pinbot machine. It has no battery damage but was missing several parts (mostly lighting section and some parts for the solenoids and switch matrix) and had some previous work done. I repopulated the missing parts for the lighting section and replaced all the bad parts I could find. After things looked good with an initial bench test I installed it in my Pinbot (which was working well) while I replaced a couple caps on my original board.

Board boots up with no errors now and as far as I can tell all the lighting, solenoids, and switch matrix are working perfect. I can add credits and play normal games. Only issue is that there is no sound at all. I do hear a sight hum in the audio that I normally would but nothing else. No background sounds, music, or speech.

On of the parts that had previously been replaced is the PIA at U9. I wasn't sure of that original work so I carefully undid that and installed a new machined pin socket with a know good PIA. I also verified the sound ROM's are good. Perhaps that sound was having issues before and that's why they tried replacing U9.

Since all the sound works well with the other main board installed this is something on the main board. There is a ton of information about other areas of System 11 repair but I haven't found a lot on the sound sections (except how they changed from game to game)

Has anyone run into this symptom before? Before I start replacing parts I want to see if there are any suggestions on the most likely culprit. U1, U2, U3, U4, U5? Since the board comes up with no errors and I ca get to the test sections to run the music and sound tests for the moment I am making the assumption that the CPU and U24, RAM at U23, and the sockets for the EPROMs are ok and that section is running.

Any help is appreciated.

Robert

#2 6 years ago

Well, I had my original heavily battery damaged board that I kept for parts. I pulled off U1, U2, U3, U4, U5 from that board and swapped them onto this one. Now I have most of the sounds (but not all) with the exception of the speech. So it seems that the audio is now coming through ok from the separate sound board for all the background music but nothing from the CPU board yet.

Still more to troubleshoot....

Robert

#3 6 years ago

Had to resolder one pin on the chips I moved over and I got it. All seems to be working well now....

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