Electronics > Repair
DSO-X 3024A Power Supply defect
georges80:
It's mostly self evident once you have the scope opened up and remove the dead PS. There's a few wires/connections.
Mains input, Front panel low voltage on/off control, +12/0V main DC power and sense wires. If you are competent enough to use the scope then you can handle the re-wiring :)
Most of the work is getting the new supply to fit nicely (with the re-wiring) into the rather cramped space. Take your time.
cheers,
george.
gman76:
Hi georges80, I'm buying the RPSG-160-12. I took the original supply out and looked at the CCH125 pinouts. Everything looks obvious except the pin called REMOTE on the 1x6 header. There are 3 wires coming from the main board into the CCH125, -S +S and REMOTE.
On the RPSG-160, I see two possibilities: PG and PS/ON. I think its the PS/ON that I need to connect the REMOTE wire to, correct? The pin called PG looks like an output. If this is the case, then I'll need to remove the 3 wires from the orig connector and place the two sense wires in a new housing and the REMOTE wire into another housing since the RPSG has these split into two connectors.
2N3055:
--- Quote from: gman76 on February 22, 2021, 11:37:34 pm ---Hi georges80, I'm buying the RPSG-160-12. I took the original supply out and looked at the CCH125 pinouts. Everything looks obvious except the pin called REMOTE on the 1x6 header. There are 3 wires coming from the main board into the CCH125, -S +S and REMOTE.
On the RPSG-160, I see two possibilities: PG and PS/ON. I think its the PS/ON that I need to connect the REMOTE wire to, correct? The pin called PG looks like an output. If this is the case, then I'll need to remove the 3 wires from the orig connector and place the two sense wires in a new housing and the REMOTE wire into another housing since the RPSG has these split into two connectors.
--- End quote ---
PG is power good output. Remote is ON/OFF..
rolkinas:
Regarding original PSU.
I experimented with higher value resistors in place of cooking 4pcs 22K. AC voltage controlled by variac. Resistor values and corresponding psu start stop voltages below:
220k - start 80Vac , stop 75Vac
310k - start 98Vac , stop 75Vac
440k - start 135Vac , stop 75Vac
660k - start 190Vac , stop 75Vac
750k - start 217Vac , stop 75Vac
NOTICE: Tested ohmic values are total resistance for all 4 resistors (because all 4 all are in series). So 220K means 4pcs of aproximately 56k
When psu starts, voltage drop across resistors becomes near 380V because PFC starts as well.
turn off voltage is determined by PFC
Even with 220k resistor stayed at about 70 degree C what is much more usable {hint to 110Vac grid fellas :) }
gman76:
Received the Meanwell RSPG160 supply, expanded holes to get the screw holes lined up, re-arranged wiring on connector. Plugged it into 120VAC, not sure if it would go bang, but quietly powered up. Scope is now back up and running.
Worked fine at 12.0V., but adjusted Vout up to 12.6V.
The only issue now is that the front power button doesn't work. I probed the REMOTE signal (PS/ON) and it's always low. Pushing the power switch doesn't change the DMM reading, just slightly. Maybe need a GND return? Or is this the wrong signal?
EDIT: It was indeed the ground connection of the 1x4 header (CN901). I made a wire with a crimp on each end. Front power button works great.
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