I recently replaced some bad components in an MTX 4160 amplifier. Two power supply fets, two burned out gate resistors, and two shorted BUZ11 outputs.
After all was changed, I went to power it up and my DC power supply started kicking out all sorts of voltage! This is a new power supply that was given to me and it has variable DC and AC ouputs at 5 amps. It's made by Alpha Magnetics, but I cannot find much info online about it.
Anyway, as soon as the DC power supply sees a capacitive load, the voltage starts ramping up. If I disconnect the amp and use a resistor dummy load, it works great, voltage is stable. I opened it up and it appears to be a triac controlled unit with a heftly transformer.
I decided to bypass the DC circuitry and I built my own MUR860 rectifier and used the AC ouputs. All is well, voltage is good, UNTIL I connect the amp! Is it possible the amplifier is somehow causing the power supply to malfunction?
I took some voltage readings and with the AC voltage at 5 volts I somehow manage to get over 20V DC on the other side of the rectifier with the amplfier connected. Don't ask me how this happens, I am STUMPED!
I "pulse width modulated" the darn thing by turning it on and off really fast while monitoring the multi-meter and the amplfier turns on between 11-14 or so volts. It seems the amp is working, but my power supply isn't.
After all was changed, I went to power it up and my DC power supply started kicking out all sorts of voltage! This is a new power supply that was given to me and it has variable DC and AC ouputs at 5 amps. It's made by Alpha Magnetics, but I cannot find much info online about it.
Anyway, as soon as the DC power supply sees a capacitive load, the voltage starts ramping up. If I disconnect the amp and use a resistor dummy load, it works great, voltage is stable. I opened it up and it appears to be a triac controlled unit with a heftly transformer.
I decided to bypass the DC circuitry and I built my own MUR860 rectifier and used the AC ouputs. All is well, voltage is good, UNTIL I connect the amp! Is it possible the amplifier is somehow causing the power supply to malfunction?
I took some voltage readings and with the AC voltage at 5 volts I somehow manage to get over 20V DC on the other side of the rectifier with the amplfier connected. Don't ask me how this happens, I am STUMPED!
I "pulse width modulated" the darn thing by turning it on and off really fast while monitoring the multi-meter and the amplfier turns on between 11-14 or so volts. It seems the amp is working, but my power supply isn't.
What happens if you connect both the dummy load AND the amplifier to the supply? If the output is not happy with the amp as a load, maybe the resistor will help lower the overall reactance and the supply will work properly.
You may also want to try connecting a diode in series with the DC output to see if the high voltage is coming from the supply or if it's only on the amplifier side of the diode.
You could try connecting the amp to a battery. Do so via a 10 amp fuse in case there is an unknown fault in the amp. Clamp the FETs to the sink before applying power.
You may also want to try connecting a diode in series with the DC output to see if the high voltage is coming from the supply or if it's only on the amplifier side of the diode.
You could try connecting the amp to a battery. Do so via a 10 amp fuse in case there is an unknown fault in the amp. Clamp the FETs to the sink before applying power.
I did indeed connect the amp with the dummy load, but it still didn't like it. The dummy load is a 1K 10 watt resistor. I'm going to lower that to maybe 100 or even 50 ohms.
I will also try an inline diode and see what it does.
The next few days are busy so it might be a week before I try it, but that will give me some time to think about it some more.
thanks for the tips Perry.
I will also try an inline diode and see what it does.
The next few days are busy so it might be a week before I try it, but that will give me some time to think about it some more.
thanks for the tips Perry.
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