SMPS Troubleshooting steps
Guys
I'm back after some more troubleshooting of my plasma smps.
This has three outputs
1. 80V regulated by the switcher
2. 60V which has its own DC to DC converter teed of the 80V line
3. Vcc +5V which tees of the 60V line
If I switch on the unit with all three rails connected, then the unit goes into protection almost as soon as I hear the soft start relay kick in. You can see a momentary square wave on the gate of the switching transistor then nada. Measurement of of the outputs shows zero volts.
Resistance checks of the outputs of the three rails against ground using the diode check setting of my DMM show
1. 80V line =1Meg Ohm
2. 60V line =1Meg Ohm
3. 5V line =1Meg Ohm
I then wired a 250V halogen bulb in series with the 80V rail to see if I have too much of a current draw, and interestingly enough the unit has gone into a power cycle every 4 seconds or so.
After turn on, the switching transistor kicks in as expected, and I get a nice square wave on the gate of the switching transistor ahead of the fly-back transformer. The Halogen bulb lights up.
After about four seconds I hear a tingly sort of click and the square wave disappears. and the Halogen bulb goes out.
on observing the 80V line with the DMM, I see that it starts of at 81.4V and then when it gets to 81.7V the click happens and the power cycles the volts drop immediately to zero
on observing the 60 line with the DMM, I see that it sits at 60.7 V until the click happens and the power cycles and drops immediately to zero
The 5V line stays at 5V constantly
On observing the square-wave on the switching transistor it start of with a large mark space ratio, and then progressively gets smaller (higher frequency) until the click.
Am I right in the following assumptions ?
1. Output caps on the 80V line are bad as it drops off to Zero too quickly.
2. No problem with the circuit board the smps is connecting to, rather an issue with the SMPS unable to hold a load.
3. A potential Over-voltage issue with the SMPS
Thanks for any thoughts
Mike C
Guys
I'm back after some more troubleshooting of my plasma smps.
This has three outputs
1. 80V regulated by the switcher
2. 60V which has its own DC to DC converter teed of the 80V line
3. Vcc +5V which tees of the 60V line
If I switch on the unit with all three rails connected, then the unit goes into protection almost as soon as I hear the soft start relay kick in. You can see a momentary square wave on the gate of the switching transistor then nada. Measurement of of the outputs shows zero volts.
Resistance checks of the outputs of the three rails against ground using the diode check setting of my DMM show
1. 80V line =1Meg Ohm
2. 60V line =1Meg Ohm
3. 5V line =1Meg Ohm
I then wired a 250V halogen bulb in series with the 80V rail to see if I have too much of a current draw, and interestingly enough the unit has gone into a power cycle every 4 seconds or so.
After turn on, the switching transistor kicks in as expected, and I get a nice square wave on the gate of the switching transistor ahead of the fly-back transformer. The Halogen bulb lights up.
After about four seconds I hear a tingly sort of click and the square wave disappears. and the Halogen bulb goes out.
on observing the 80V line with the DMM, I see that it starts of at 81.4V and then when it gets to 81.7V the click happens and the power cycles the volts drop immediately to zero
on observing the 60 line with the DMM, I see that it sits at 60.7 V until the click happens and the power cycles and drops immediately to zero
The 5V line stays at 5V constantly
On observing the square-wave on the switching transistor it start of with a large mark space ratio, and then progressively gets smaller (higher frequency) until the click.
Am I right in the following assumptions ?
1. Output caps on the 80V line are bad as it drops off to Zero too quickly.
2. No problem with the circuit board the smps is connecting to, rather an issue with the SMPS unable to hold a load.
3. A potential Over-voltage issue with the SMPS
Thanks for any thoughts
Mike C