Re: Power supply build quality pictorial. part 2
So, we've looked at switching power supplies, now let's look at a lab bench linear power supply.
I've owned this thing for about 18 months, but it was second hand, so no idea how old it really is.
It is a 0-35V 0-3A constant-voltage/constant-current power supply, manufactured by Tagasaki of Japan. The model number is GM035-3. And it only cost me £30. I can find very little information on the internet about this model, so I suspect it's mid 1980s, especially given the Chemicon caps in it are mostly SM series, which was obsoleted a while back.
The engineering in this thing is fantastic. The transformer is huge - especially for a 105W max output! There are three Toshiba power transistors in parallel on a massive heatsink (with OR-ing resistors), controlled by one main board. Current sensing is high side, not some low side stuff which might ignore earth shorts. (The output can be fully floated, which has been useful several times.) And a very clever way of reducing the power dissipated in the transistors: two SCRs select between three taps on the power transformer, reducing the input voltage to the transistors at lower output voltages. The control logic is surprisingly simple, comprising a few op-amps and a TL431 reference. The potentiometers on the front are only single turn, but I haven't needed precision from it yet, especially given the gauges are only useful as a general guide.
I'm impressed at how low noise it is (below the noise floor of my scope in most cases, even approaching full load), how reliable it has been (no problems, even after shorting the output @ 35V so many times), and how well built it is.
I've run a universal motor off this drawing 2A at 35V. That's the maximum output load I've been able to demand from it so far, and it coped very well. My only wish now would be for a higher output voltage, up to 60V (SELV limit, but still painful!), for testing some high voltage input dc-dc converters. And blowing up cheap Chinese PSU fans
. (Sometimes, 35V isn't enough!)
So, we've looked at switching power supplies, now let's look at a lab bench linear power supply.
I've owned this thing for about 18 months, but it was second hand, so no idea how old it really is.
It is a 0-35V 0-3A constant-voltage/constant-current power supply, manufactured by Tagasaki of Japan. The model number is GM035-3. And it only cost me £30. I can find very little information on the internet about this model, so I suspect it's mid 1980s, especially given the Chemicon caps in it are mostly SM series, which was obsoleted a while back.
The engineering in this thing is fantastic. The transformer is huge - especially for a 105W max output! There are three Toshiba power transistors in parallel on a massive heatsink (with OR-ing resistors), controlled by one main board. Current sensing is high side, not some low side stuff which might ignore earth shorts. (The output can be fully floated, which has been useful several times.) And a very clever way of reducing the power dissipated in the transistors: two SCRs select between three taps on the power transformer, reducing the input voltage to the transistors at lower output voltages. The control logic is surprisingly simple, comprising a few op-amps and a TL431 reference. The potentiometers on the front are only single turn, but I haven't needed precision from it yet, especially given the gauges are only useful as a general guide.
I'm impressed at how low noise it is (below the noise floor of my scope in most cases, even approaching full load), how reliable it has been (no problems, even after shorting the output @ 35V so many times), and how well built it is.
I've run a universal motor off this drawing 2A at 35V. That's the maximum output load I've been able to demand from it so far, and it coped very well. My only wish now would be for a higher output voltage, up to 60V (SELV limit, but still painful!), for testing some high voltage input dc-dc converters. And blowing up cheap Chinese PSU fans
. (Sometimes, 35V isn't enough!)
Attached Files
Half of the computer problems is caused by bad contacts 
Voltages are fine, the fan runs at full speed all times.
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