Hi ladies and gentlemen,
I purchased a Digitech RV 1000 Guitar Effects processor off this guy which are run from external power packs.
And after I got it home, I found it had a rouge power supply connected. The proper power supply should be 9 Volts AC (Yes AC) 1.3 Amps, but the seller had a 15 Volt DC (Yes DC) 1.34 Amp connected.
Technically this is a mismatch and my first reaction was, why didn't it french fry the unit. But the unit seemed to function fine. (But I wasn't going to risk it, regardless of the sellers assurance) But here is my question.
What would be electronically happening in this scenario? The reason I ask is because at first I was thinking "Alarm bells" someone call the fire department...but later when thinking about the circuit, I thought "what, if any harm could this potentially do to the input circuit" after all the only real difference (Besides the 15Votls being on the high side) is that the Rectification is housed externally.
So pooling my aging electronics theory, I wondered about doing some theory on it. Here is what I came up with. I would love any input.
First for the unit to have an external AC supply pack, there is a Full Wave Rectifier internally. So what happens when a DC signal is connected to Full Wave Bridge Rectifier? Normally, an AC signal is connected to obtain a DC signal then filtered, regulated. And only on every half cycle are 2 of the 4 Diodes working at the given frequency. But feeding a DC signal in would mean that only half of the FWBR (Full Wave Bridge Rectifier) would ever see a signal. (The positive signal)
So theoretically just how bad of a mismatch was this after all? (Some rough calculations)
15Votts DC was being feed into the FWBR, minus 2 x 0.7 volts to forward bias the diodes. Therefore 15 Volts input minus 1.4Volts leave the units input as 13.6 Volts. So the Filtering Cap would have been reading around 13.6 Volts.
Hmmmm??? Still way to high as far as I can see.
Anyone know roughly what the output of a FWBR would see being feed 9 Volts AC ? Would it be 9V minus 1.4V leaving an output of 7.6Volts being seen on its output?
This would be basic theory for some no doubt. But the point is that maybe feeding an electronic appliance a DC Voltage, (Under the right circumstances) even though, it calls for an AC supply, may not harm a circuit at all. In fact, it could be seen as a handy trick to have up your sleeve if you've misplaced your power supply and need something quick and handy.
However, reversing the scenario, whereby feeding an electronic appliance an AC signal when I calls for a DC input could be a disaster. (No rectification?)
Anyone additional thoughts on this, please feel free.
Steve
I purchased a Digitech RV 1000 Guitar Effects processor off this guy which are run from external power packs.
And after I got it home, I found it had a rouge power supply connected. The proper power supply should be 9 Volts AC (Yes AC) 1.3 Amps, but the seller had a 15 Volt DC (Yes DC) 1.34 Amp connected.
Technically this is a mismatch and my first reaction was, why didn't it french fry the unit. But the unit seemed to function fine. (But I wasn't going to risk it, regardless of the sellers assurance) But here is my question.
What would be electronically happening in this scenario? The reason I ask is because at first I was thinking "Alarm bells" someone call the fire department...but later when thinking about the circuit, I thought "what, if any harm could this potentially do to the input circuit" after all the only real difference (Besides the 15Votls being on the high side) is that the Rectification is housed externally.
So pooling my aging electronics theory, I wondered about doing some theory on it. Here is what I came up with. I would love any input.
First for the unit to have an external AC supply pack, there is a Full Wave Rectifier internally. So what happens when a DC signal is connected to Full Wave Bridge Rectifier? Normally, an AC signal is connected to obtain a DC signal then filtered, regulated. And only on every half cycle are 2 of the 4 Diodes working at the given frequency. But feeding a DC signal in would mean that only half of the FWBR (Full Wave Bridge Rectifier) would ever see a signal. (The positive signal)
So theoretically just how bad of a mismatch was this after all? (Some rough calculations)
15Votts DC was being feed into the FWBR, minus 2 x 0.7 volts to forward bias the diodes. Therefore 15 Volts input minus 1.4Volts leave the units input as 13.6 Volts. So the Filtering Cap would have been reading around 13.6 Volts.
Hmmmm??? Still way to high as far as I can see.
Anyone know roughly what the output of a FWBR would see being feed 9 Volts AC ? Would it be 9V minus 1.4V leaving an output of 7.6Volts being seen on its output?
This would be basic theory for some no doubt. But the point is that maybe feeding an electronic appliance a DC Voltage, (Under the right circumstances) even though, it calls for an AC supply, may not harm a circuit at all. In fact, it could be seen as a handy trick to have up your sleeve if you've misplaced your power supply and need something quick and handy.
However, reversing the scenario, whereby feeding an electronic appliance an AC signal when I calls for a DC input could be a disaster. (No rectification?)
Anyone additional thoughts on this, please feel free.
Steve
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