Sixtysixdeuce
New Member
Hi guys (and gals?). My name is Nick, and I'm a mechanic with a hobbiest interest in electronics. Unfortunately, my knowledge is not terribly advanced in contrast to what I expect I'll find here, which is my reason for signing up. The project I have right now is one you'll all probably get a chuckle out of, and most people would suggest simply replacing the broken unit, I think. But I don't like not being able to solve problems, which sometimes means enlisting the help of more knowledgeable folks. Ask me to find the problem with your car, I will. But we don't typically repair the internals of control modules on them, just replace the units. So logic circuits I'm still learning.
Anyway, my query. The item in question is a baby swing, fisher-price nature's touch model (6v DC). I have been unable to turn up a schematic, not even with a call to Mattel's tech service department. So I was left trying to figure out the problem for myself. I'm sure for some of you, this is very elementary, but I'm kinda lost. Problem started when batteries were installed backwards. The sound functions still work, as does the simple mobile motor circuit (just an on/off) The issue is with the swing. It uses a small DC brush motor, but instead of being controlled with a potentiometer, it uses a logic circuit with a couple dozen resistors, 8 capacitors, 3 large and 4 small 3-node transistors (both NPN and PNP), one diode, a small calibrating potentiometer, what appears to be a and one LM324N quad op Amplifier. The issue is that, when turned on and with the motor load, it has voltage only briefly, which then tapers off to nothing. At first, I traced that back to one of the resistors. It had 2.3v in and no out. So I simply bridged it. Well, then the drop happened at the next resistor back in the line. So I bridged it too. Same thing. I got all the way back to the amplifier, which will lose voltage at the 8, 9 and 10 terminals when the two resistors are bypassed. I figured the amplifier was dropping because of heat caused by some internal damage with the inverse voltage, so I replaced it. Same thing still happens.
I suppose my biggest question would be what component was most likely damaged by the voltage inversion? I know this is even more difficult without looking at a schematic or the physical unit, but figured it was worth a shot. I've exhausted my diagnostic capabilities but would rather learn something than do the logical thing and simply throw it away.
Here are a few images of the PCB's. For the insulated wires, the distribution is as follows:
Black-ground
Red-6v+
Blue and white-Mobile motor
Orange (2)-Speaker
Green-Swing motor ground
Yellow-Swing motor power
Since three of the text boxes of the first image came out fuzzy, they simply indicate wires (purple) for the auxiliary position on the swing switch, which allows mobile and sound without swing motion, one pointing to a component that I'm not sure if it's a resistor of sorts or a small transformer coil (It is tiny copper wire wound around an insulator), and one indicating the volume potentiometer at the bottom center.
**broken link removed**
**broken link removed**
**broken link removed**
In the following image, I've attached arrows and numbers to show where the voltage drop happens. The circuit goes straight to the swing motor from point 1. At point 1, the initial drop happens. It'll be 2.3 v on the in side, and drop to 0 on the out. If I bridge that resistor, the voltage will drop to zero at point 2. If I bridge the resistor at point 2, voltage will drop at the three point indicated by #3. I never lose ground or 6v at VCC input, or the other inputs and outputs at the amplifier.
**broken link removed**
Thanks in advance for your help!
Anyway, my query. The item in question is a baby swing, fisher-price nature's touch model (6v DC). I have been unable to turn up a schematic, not even with a call to Mattel's tech service department. So I was left trying to figure out the problem for myself. I'm sure for some of you, this is very elementary, but I'm kinda lost. Problem started when batteries were installed backwards. The sound functions still work, as does the simple mobile motor circuit (just an on/off) The issue is with the swing. It uses a small DC brush motor, but instead of being controlled with a potentiometer, it uses a logic circuit with a couple dozen resistors, 8 capacitors, 3 large and 4 small 3-node transistors (both NPN and PNP), one diode, a small calibrating potentiometer, what appears to be a and one LM324N quad op Amplifier. The issue is that, when turned on and with the motor load, it has voltage only briefly, which then tapers off to nothing. At first, I traced that back to one of the resistors. It had 2.3v in and no out. So I simply bridged it. Well, then the drop happened at the next resistor back in the line. So I bridged it too. Same thing. I got all the way back to the amplifier, which will lose voltage at the 8, 9 and 10 terminals when the two resistors are bypassed. I figured the amplifier was dropping because of heat caused by some internal damage with the inverse voltage, so I replaced it. Same thing still happens.
I suppose my biggest question would be what component was most likely damaged by the voltage inversion? I know this is even more difficult without looking at a schematic or the physical unit, but figured it was worth a shot. I've exhausted my diagnostic capabilities but would rather learn something than do the logical thing and simply throw it away.
Here are a few images of the PCB's. For the insulated wires, the distribution is as follows:
Black-ground
Red-6v+
Blue and white-Mobile motor
Orange (2)-Speaker
Green-Swing motor ground
Yellow-Swing motor power
Since three of the text boxes of the first image came out fuzzy, they simply indicate wires (purple) for the auxiliary position on the swing switch, which allows mobile and sound without swing motion, one pointing to a component that I'm not sure if it's a resistor of sorts or a small transformer coil (It is tiny copper wire wound around an insulator), and one indicating the volume potentiometer at the bottom center.
**broken link removed**
**broken link removed**
**broken link removed**
In the following image, I've attached arrows and numbers to show where the voltage drop happens. The circuit goes straight to the swing motor from point 1. At point 1, the initial drop happens. It'll be 2.3 v on the in side, and drop to 0 on the out. If I bridge that resistor, the voltage will drop to zero at point 2. If I bridge the resistor at point 2, voltage will drop at the three point indicated by #3. I never lose ground or 6v at VCC input, or the other inputs and outputs at the amplifier.
**broken link removed**
Thanks in advance for your help!
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