I have recapped the monitor and now I'm waiting for some more tools so I can adjust the monitor when running (a blog post about the monitor will come after it is adjusted). I discovered that poking around in the monitor chassis with metal tools was not the best idea. I was adjusting the horizontal hold and touched the RF shield, I heard a pop, and the monitor went black. Luckily enough all it took was a restart of the monitor to get it up and running again, but I do not dare to adjust it any more with metal tools, so I ordered a kit of plastic adjustment tools so now I'm waiting for them before working any more with the monitor
Until then I decided to take a look at the soundboard that did not work.
I had several issues with the sound card
- It did not sound anything at all
- One fuseholder was broken
- The volume control was inverted and has very short cables, I also missing the metal bracket to fasten it to the cab.
When I first got the game I noticed that there were cables hanging from the soundboard that held a fuse, looking closer I noticed that the fuseholder was broken.
So the first thing I did was to replace the broken fuseholder.
I then hooked up the soundboard to a simple testbed that I made and started to test it.
All voltages looked good when testing at the testpoints.
In the image below you can see the testing points. They are numbered 1 to 4 where 1 is to the left and 4 is to the right.
| Testpoint | Voltage |
|---|---|
| 1 | +12V |
| 2 | -12V |
| 3 | GND |
| 4 | +5V |
All voltages checked out fine but there were still no sound.
The board in the image below, that is a donor board that I have, therefore the wrong ROM chip ;)
Next thing to check is the audio amplifier, so I turned the volume up, and was touching the legs of IC1 with my fingers, I heard some noice in the speaker so I then assumed that the main problem was not the amplifier, I then did the thing that you always should start with: reseat all circuits that sits in a socket. And that did it. So the board was not broken, the processor and/or the rom, just needed to be reseated.
While at it, I also changed the speaker from a replaced speaker, half the size it should be and that one also had a broken cone. I bought a new 6,5" full range speaker and mounted it, hopefully it will sound a lot better than the broken one.
Still need to change the speakergrille and the volume pot, but that will be another day.