Originally purchased this working from Farnell from clearance for low price. Bought this to experiment with some high voltage Tesla coil stuff. Also, I have a problem with collecting test equipment.
Got it home and found it was popping fuses. Took it back to the shop, they tried a new fuse and it popped again. So they refunded me and let me keep the broken unit...so lets now figure out what's gone wrong here.
It's a switchmode supply with an adjustable output voltage. The supply works like a normal PC ATX supply, it appears to use a two-switch half bridge (capacitor coupled) converter with a transformer gate driver. The pre-converter supply generates an output voltage some volts above the desired output with ripple and noise. A pass transistor then regulates the output (removing ripple and improving transient performance) and provides current limiting functionality.
All four bridge diodes test OK. The two main switching transistors are dead short, as expected. NTCs and caps test OK. The capacitors appear to be a mix of Chemicon, Rubycon and some odd Chinese brand with a Rubycon vent, though the Rubycon caps all look a little off, so they could be fakes.
There's a standby/aux supply which powers the logic and displays. The fan operates off a separate tap on the main supply - I guess the idea is as the output voltage goes up the fan speed goes up too. Neat way of doing that, I guess. But this will mean the fan won't operate until the supply reaches something like 100V (assuming it starts spinning around 5V), which is already a pretty decent amount of internal power dissipation. I don't know why they don't just run it off the aux supply...it would be easy enough to add temperature control too.
The anemic input filter is surprising for a piece of test equipment, and the caps across the input are not X-caps, nor do they have the required discharge resistors. There is no way this thing would ever pass CE / LVD!!
Since the supply is designed to withstand a dead short at maximum output voltage, the pass transistor needs to be rated for the maximum output voltage across its drain and source with a 1 amp current limit. This means it has to dissipate a peak power of over 300 watts. I have a great deal of doubt that the transistor can manage that! Especially given that at 1 amp, the output capacitor will take at least 100ms to discharge. So, the transistor will have to dissipate >150W for 100ms. Ha. It won't survive many short circuits doing that.
All main input and output wires are soldered directly onto the PCB - these guys have not heard of using connectors for this stuff. There's a 115/230V switch at the back, but that's at the correct setting. The 600V transistors would likely survive if the supply were set to the wrong voltage, but the main caps would probably pop since they're only 250V a piece.
The RRP for this is £500+VAT - I would feel very ripped off if I'd bought this full price!
Got it home and found it was popping fuses. Took it back to the shop, they tried a new fuse and it popped again. So they refunded me and let me keep the broken unit...so lets now figure out what's gone wrong here.
It's a switchmode supply with an adjustable output voltage. The supply works like a normal PC ATX supply, it appears to use a two-switch half bridge (capacitor coupled) converter with a transformer gate driver. The pre-converter supply generates an output voltage some volts above the desired output with ripple and noise. A pass transistor then regulates the output (removing ripple and improving transient performance) and provides current limiting functionality.
All four bridge diodes test OK. The two main switching transistors are dead short, as expected. NTCs and caps test OK. The capacitors appear to be a mix of Chemicon, Rubycon and some odd Chinese brand with a Rubycon vent, though the Rubycon caps all look a little off, so they could be fakes.
There's a standby/aux supply which powers the logic and displays. The fan operates off a separate tap on the main supply - I guess the idea is as the output voltage goes up the fan speed goes up too. Neat way of doing that, I guess. But this will mean the fan won't operate until the supply reaches something like 100V (assuming it starts spinning around 5V), which is already a pretty decent amount of internal power dissipation. I don't know why they don't just run it off the aux supply...it would be easy enough to add temperature control too.
The anemic input filter is surprising for a piece of test equipment, and the caps across the input are not X-caps, nor do they have the required discharge resistors. There is no way this thing would ever pass CE / LVD!!
Since the supply is designed to withstand a dead short at maximum output voltage, the pass transistor needs to be rated for the maximum output voltage across its drain and source with a 1 amp current limit. This means it has to dissipate a peak power of over 300 watts. I have a great deal of doubt that the transistor can manage that! Especially given that at 1 amp, the output capacitor will take at least 100ms to discharge. So, the transistor will have to dissipate >150W for 100ms. Ha. It won't survive many short circuits doing that.
All main input and output wires are soldered directly onto the PCB - these guys have not heard of using connectors for this stuff. There's a 115/230V switch at the back, but that's at the correct setting. The 600V transistors would likely survive if the supply were set to the wrong voltage, but the main caps would probably pop since they're only 250V a piece.
The RRP for this is £500+VAT - I would feel very ripped off if I'd bought this full price!
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