PCB Repair: NBA Hangtime
Problem
Barely discernible sound.
Diagnosis
As with other Midway games of the time, the audio section of the Wolf Unit PCB requires -5V. Before testing the PCB, my -5V supply was confirmed working.
I first verified the digital section of the audio system to ensure that the audio produced by the ADSP-2105 DSP was both present and correct. I captured the serial data fed to the AD1851 DAC by the DSP with my logic analyzer and converted it to an audible format:
This confirmed that the fault lay either at or beyond the analog output stage of the DAC.
As I had an UMK3 PCB to hand, I decided to make my life easier by checking various signals around the audio section so I would know what to expect from a working PCB. Somewhat mysteriously however, UMK3 had suddenly developed the same sound fault as NBA. It quickly dawned on me that NBA had killed the -5V output of my JAMMA SuperGun. Arse! I then did what I should have done right at the start: measure the resistance between -5V and ground on the PCB. The reading was 0Ω. No wonder…
In the meantime, a short funeral service was held for the dead DC-DC converter on the SuperGun that was responsible for producing the -5V supply, and a new replacement was hastily ordered from eBay.
We still needed to find the short on the PCB. There was what appeared to be a 10µF filter capacitor for the -5V supply at C10. The resistance across it measured 0Ω, so I removed it to test out of circuit and got the same result. The next morning I took a trip to my local electronics surplus store and found a suitable replacement. After installing it, I confirmed that the audio was fixed using my old JAMMA test rig, which has a working -5V supply but no video output…
Fix
Replace 10µF 10V B3528 SMD tantalum capacitor at C10.
Hi Philip, This is a great help! I actually having a hard time with a board that a bad seller sold me time ago. It supposed to be repaired but it is a mess that Im trying to fix.
One of the problem is that 10µF SMD, the same you mention here, it was solder in invert polarity also inspecting the board I found that several other small SMD where missing and instead the guy bridge them with tin 😦
I having a hard time finding the capacitors, I couldn’t find them by the name you post here.
Wondering if you can sell me a couple of them or put me in a online store to get them ?
Thanks and keep posting all this great info. Is the only place in all Internet.
Glad to be of help. I’ve updated the post with the specific type of capacitor used.