Need some troubleshooting help on my Harleem Globetrotter sound board AS-2518-50

After setting the pin up after 1.5 yr storage I don't have any sound. Can get some scratchy sounds from speaker when adjusting volume RT3 and a couple squeaks from adjusting RT2 sustain pot.

Reflowed header pins. Have the appropriate voltages 5v, 12v, 43v at all test points except TP5 has no solenoid return voltage.

CR 4 looks a little toasty from the R22 resistor below it. I have a cap rebuild kit...is that the next step to replace all 6 capacitors?

Thanks,

Eric

Thanks Cody. Here's my measurements, only pin 12 is below the 3.5V limit.

pin 1 = 3.85 vdc
pin 2 = 4.10 vdc
pin 3 = 3.82 vdc
pin 4 = 3.80 vdc
pin 12 = 3.29 vdc

That point to what's wrong?

Eric

And you are correct TP5 is connected to pin 15 and the big capacitor

Recapped the board and have some improvement. Have hum that I can change volume and tone with pots on the board. Sound test gives some warbling sounds. Test point voltages:

TP1= 5.15vdc
TP3 = 11.54vdc
C17 = 67.5vdc
R3/R5 junction 1.18vdc
U9 pin 2 = 5.85vdc
U11 pin 5 = 5.15vdc
U11 pin 9 = 0.03vdc
U11 pin 11 = 3.82vdc
Shorted U8 pins 1+2 gave no sound

Here's the board...it did work before storage

Thanks,

Eric

AS_2518_50_HGT_Sound_Board_(resized).jpg

Hey Andrew,

In that section, says check for pulsing...so I need a logic probe and can't be done with a voltmeter?

Eric

I will do that and report back. Thx!

Andrew,
Here are my measurements. Where I have a range the voltage was jumping around so I tried to capture the low and high. Let me know your thoughts.

U1 pin 4= 2.43
U7 pin 3 = 1.87-2.02
U2 pin 4 = 1.33-3.44
U2 pin 3 = 1.63-3.74
U3 pin 10 = 1.41-4.11
U3 pin 2 = 0.31-2.45
U5 pin 12 = 0.52-2.78
U4 pin 12 = 0.01-1.69
U11 pin 11 = 3.82
R3/R5 = 1.17

Does any of that stand out as problematic?

Eric

Resistors are 4.63K and 77.1 ohms. The CR4 I misread the silkscreen, it was the C6 capacitor that was brown but I changed it.

Input connectors on the sound board were reflowed....do you mean the other end of the harness on the MPU or Solenoid driver boards?

How can I tell if the PROM is bad? The sound test makes some garbled noise. Would it do anything if that was corrupt?

Eric

Measurements were taken in sound test mode.

Tried to upload a clip here

If there are connector issues would the sound test be affected? What connectors should be inspected?

Any suggestions would be great.

Thanks Andrew. I'll probably start with U11 since it was not changing voltage but just solid.

I'll let you know if there is any change.

Eric

OK that's good to know. Think I'll look harder for my logic probe to make sure that's what the issue is. It is somewhere in a box since I've never used it. Time to find it and give it a work out.

A big thank you to Cody_Chunn for all his help diagnosing the sound board issue and busting my logic probe cherry!

Also thanks to Andrew barakandI for the link and input about which chip to focus on.

Turned out U11 was not pulsing like it was supposed to. Had a couple spare parts sound boards that came with this pin in various states of disrepair. Removed the U11 from one of those and put in in my board. Even put socket strips just in case I had to try the other parts chip or buy a new chip. Viola, working!!

Isn't Pinside great?

Eric

IMG_1078_(resized).JPG

I'll PM you