AC adaptor compatibility
I have some sound modules and processors which take 9VAC which are usually rated `1 amp or 850ma. A no longer used modem PSU was rated 10.2VAC 900ma output so I thought it might be fine as a backup for my five Kurzweil MicroPianos and many of my Alesis drum modules. I wanted to know if the extra voltage would damage the units. I have been told that the amperage draw is important and not to under power in amps. Thanks, John Poole wyncoteacademy.org faculty
I have some sound modules and processors which take 9VAC which are usually rated `1 amp or 850ma. A no longer used modem PSU was rated 10.2VAC 900ma output so I thought it might be fine as a backup for my five Kurzweil MicroPianos and many of my Alesis drum modules. I wanted to know if the extra voltage would damage the units. I have been told that the amperage draw is important and not to under power in amps. Thanks, John Poole wyncoteacademy.org faculty
AC adaptor compatibility
Will do. I was always baffled why the readout using a $20 meter read way higher on most of my PSUs. I'm careful to match the DC voltage requested on my equipment but notice that some 9VDC units read almost 12. So I'm curious to see what the readout will be on the AC to AC PSUs. How much variance is safe? John Poole
Will do. I was always baffled why the readout using a $20 meter read way higher on most of my PSUs. I'm careful to match the DC voltage requested on my equipment but notice that some 9VDC units read almost 12. So I'm curious to see what the readout will be on the AC to AC PSUs. How much variance is safe? John Poole
I replaced a dead Kurzweil 9V supply with a 12V in an emergency. The owner kept it and has been using it since.
The actual issue is not really voltage. The AC power line can vary from 110 to 132 volts. That means the 9 VAC can vary from 8.25 to 10.13 volts. So your 10.2 VAC could go as high as 11.22 VAC or 14.66 VDC after rectification. Now there are a few semiconductors that could actually fail at that voltage, but it is doubtful that any mass sold MI product would use them.
The problem is that if there is an internal regulator that the higher the voltage the greater it has to drop it, thus more heat build up.
So if the internal voltage is regulated to 9 VDC at 600 ma. (Which is about all you can get from 9VAC 850 ma.) With the 9V supply the design heat dissipation is 1.5W With the other supply the worst case is 2.5W. Now if there is internal voltage regulation, it most likely has an overheat shutdown circuit.
So your supply should work. If the Alesis parts get hot then stop using it. If they shut down and restart later don't use it.
If you can see the regulators on the cards are 78xx or 79xx they will be fine.
Of course you can check you AC line voltage. If it is 117 or below don't even worry about it.
The actual issue is not really voltage. The AC power line can vary from 110 to 132 volts. That means the 9 VAC can vary from 8.25 to 10.13 volts. So your 10.2 VAC could go as high as 11.22 VAC or 14.66 VDC after rectification. Now there are a few semiconductors that could actually fail at that voltage, but it is doubtful that any mass sold MI product would use them.
The problem is that if there is an internal regulator that the higher the voltage the greater it has to drop it, thus more heat build up.
So if the internal voltage is regulated to 9 VDC at 600 ma. (Which is about all you can get from 9VAC 850 ma.) With the 9V supply the design heat dissipation is 1.5W With the other supply the worst case is 2.5W. Now if there is internal voltage regulation, it most likely has an overheat shutdown circuit.
So your supply should work. If the Alesis parts get hot then stop using it. If they shut down and restart later don't use it.
If you can see the regulators on the cards are 78xx or 79xx they will be fine.
Of course you can check you AC line voltage. If it is 117 or below don't even worry about it.
AC to AC PSUs
I have only a layman's understanding of electricity and circuits.
I used a cheapo meter and all my Alesis PSUs read exactly 9VAC. The disused modem supply rated at 10.2 came out at 10VAC. I assume professional meters can pick up digitally an exact readout. I always scout out curbside throwaways. I got lucky and found a 14VDC supply which I can use for a Boss drum machine. Thanks for all of your input. John Poole
I have only a layman's understanding of electricity and circuits.
I used a cheapo meter and all my Alesis PSUs read exactly 9VAC. The disused modem supply rated at 10.2 came out at 10VAC. I assume professional meters can pick up digitally an exact readout. I always scout out curbside throwaways. I got lucky and found a 14VDC supply which I can use for a Boss drum machine. Thanks for all of your input. John Poole
This is suspicious.
A transformer output voltage depends on both the mains input voltage and the load. If the load is open circuit, then I would expect the open circuit voltage to vary markedly throughout the day and week.
I'm very happy with the little Tenma I got from MCM. This model, I think:
Tenma 2,000 Count 3-1/2 Digit Multimeter DMM | 72-7720 (727720) | Tenma
Tenma 2,000 Count 3-1/2 Digit Multimeter DMM | 72-7720 (727720) | Tenma
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