Hey guys,
I’m repairing a Delta DPS-300AB-81B (12 V / -53 V PSU) and I’m trying to identify a small 3-pin SMD IC marked “UY 451” on the primary side, and to confirm if it’s safe to bypass it. The original fault was 0 V on the 12 V rail and about -27 V on the -53 V rail, with about 328 VDC on the bulk cap. The primary controllers are a DAP013D for PWM and a CM6800 PFC controller. Near the DAP013D there is a 35 V electrolytic cap, one leg to primary ground, the other is a VCC node fed from the HV side via DAP013D’s internal startup (through a diode). That same node goes to one pin of the 3-pin IC (UY 451). Another pin of UY451 goes to the VCC rail that feeds both DAP013D and CM6800, and the third pin goes to main filter cap ground through a small diode.
With UY451 in circuit, both the VCC node and the IC VCC pins sit at about 9.5–10 V, which is below their UVLO threshold so the PSU never really starts. When I remove UY451 completely, the 35 V cap now charges up to around 15–16 V, which matches the expected DAP013D startup VCC. On the bench, if I feed the presumed input pin of UY451 with 15–16 V and reference the third pin to ground, the output pin sits at around 0.03 V, so it doesn’t appear to pass or regulate anything any more and looks effectively dead.
For testing, I bypassed UY451 so that the controller VCC rail is fed directly from the 15–16 V VCC cap node. With this bypass in place, after a short delay both rails come up properly: 12 V is present and stable, and -53 V is at the correct level so it looks like UY451 is the only faulty part. My questions are, does anyone recognize the SMD marking “UY 451” and know exactly what this IC is (small regulator/pass transistor/supervisor with pass element)? And is it electrically safe as a permanent repair to feed DAP013D and CM6800 VCC directly from that ~15–16 V startup node (possibly through a small series resistor), given their VCC ratings? Or would you recommend sourcing the exact part from a donor or replacing it with a simple discrete/regulator solution instead?
Thanks in advance!
I’m repairing a Delta DPS-300AB-81B (12 V / -53 V PSU) and I’m trying to identify a small 3-pin SMD IC marked “UY 451” on the primary side, and to confirm if it’s safe to bypass it. The original fault was 0 V on the 12 V rail and about -27 V on the -53 V rail, with about 328 VDC on the bulk cap. The primary controllers are a DAP013D for PWM and a CM6800 PFC controller. Near the DAP013D there is a 35 V electrolytic cap, one leg to primary ground, the other is a VCC node fed from the HV side via DAP013D’s internal startup (through a diode). That same node goes to one pin of the 3-pin IC (UY 451). Another pin of UY451 goes to the VCC rail that feeds both DAP013D and CM6800, and the third pin goes to main filter cap ground through a small diode.
With UY451 in circuit, both the VCC node and the IC VCC pins sit at about 9.5–10 V, which is below their UVLO threshold so the PSU never really starts. When I remove UY451 completely, the 35 V cap now charges up to around 15–16 V, which matches the expected DAP013D startup VCC. On the bench, if I feed the presumed input pin of UY451 with 15–16 V and reference the third pin to ground, the output pin sits at around 0.03 V, so it doesn’t appear to pass or regulate anything any more and looks effectively dead.
For testing, I bypassed UY451 so that the controller VCC rail is fed directly from the 15–16 V VCC cap node. With this bypass in place, after a short delay both rails come up properly: 12 V is present and stable, and -53 V is at the correct level so it looks like UY451 is the only faulty part. My questions are, does anyone recognize the SMD marking “UY 451” and know exactly what this IC is (small regulator/pass transistor/supervisor with pass element)? And is it electrically safe as a permanent repair to feed DAP013D and CM6800 VCC directly from that ~15–16 V startup node (possibly through a small series resistor), given their VCC ratings? Or would you recommend sourcing the exact part from a donor or replacing it with a simple discrete/regulator solution instead?
Thanks in advance!
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