Hi everyone,
I'm working on a Wurlitzer 206A with a subtle, but somewhat nagging issue. There are audio artifacts (high frequency) that sound a bit like a crackle, or static. At other times, the sound is periodic, about 3 or 4 "clicks" per second. I know that the sound isn't coming from the reed bar. The reed bar is completely disconnected from the amp board. I have traced the source of the signal to the 15V rail of the power supply. This is the only rail of power that I can pick up this sound occurring.
The board has had all electrolytic caps replaced, and this made no change in the issue. All resistors are well within tolerance.
I can see that the 15V supply is coming from a Motorola 142349 IC. Since I didn't have one of these handy, I disconnected the 15V leg of R28 and R23, and connected these to a separate 15V DC power supply. Sound disappeared.
The 22.5V and -22.5V rails are looking very good. I've replaced the 4 power supply diodes, and this smoothed out what little AC ripple it had by even less. There appears to be only 2 or 3 MV of AC ripple on these rails, and no other anomalies.
So this leads me to wonder if I can replace that voltage regulator. What's an equivalent replacement for the chip? It's got a big M on it (I assume a Motorola logo), and has part number 142349 silk screened on it. So far the most likely candidate is this one, but I'm not sure if it's all correct or not. http://www.weisd.com/test/GenericParts_WEISD_view.php?editid1=142349
I'm working on a Wurlitzer 206A with a subtle, but somewhat nagging issue. There are audio artifacts (high frequency) that sound a bit like a crackle, or static. At other times, the sound is periodic, about 3 or 4 "clicks" per second. I know that the sound isn't coming from the reed bar. The reed bar is completely disconnected from the amp board. I have traced the source of the signal to the 15V rail of the power supply. This is the only rail of power that I can pick up this sound occurring.
The board has had all electrolytic caps replaced, and this made no change in the issue. All resistors are well within tolerance.
I can see that the 15V supply is coming from a Motorola 142349 IC. Since I didn't have one of these handy, I disconnected the 15V leg of R28 and R23, and connected these to a separate 15V DC power supply. Sound disappeared.
The 22.5V and -22.5V rails are looking very good. I've replaced the 4 power supply diodes, and this smoothed out what little AC ripple it had by even less. There appears to be only 2 or 3 MV of AC ripple on these rails, and no other anomalies.
So this leads me to wonder if I can replace that voltage regulator. What's an equivalent replacement for the chip? It's got a big M on it (I assume a Motorola logo), and has part number 142349 silk screened on it. So far the most likely candidate is this one, but I'm not sure if it's all correct or not. http://www.weisd.com/test/GenericParts_WEISD_view.php?editid1=142349