I have a dead PSU.
The obvious first issue was a slightly swollen main capa (C301), which confirmed leakage when unsoldered. Replaced it, but PSU still not delivering.
I see no obvious damage to any component.
Find attached the circuit diagram.
Since I am not at all into analog PS design, I can't find what's going wrong.
My main suspects are the OP301 and Q301 ... but any advise on how to identify/confirm would be helpfull.
I measured some voltages (with 230VAC connected, no load connected) and can measure more if needed.
Note: I cannot accurately measure below 5mV, so 0 could be anuthing between 0 and 5mVDC
- output 5VD: 0VDC
- output DET: 0.1VDC
- across C301 : 335-345 VDC (as net fluctuates)
- IC301 (TOP 266EG):
- V 4.9VDC
- D ~340VDC
- C 0VDC
- X 0VDC
- F & S 0VDC (obviusly, since reference)
- directly across R307, R308, R309 I measure each time 90-92VDC, BUT strangely (checked 5 times), when measuring from 0V(IC301-S/F) to intermediate connections I get:
- 0 to IC301.V : 4.9VDC
- 0 to R309-R308 : 96VDC (consistent with above)
- 0 to R308-R307 : 189VDC (consistent with above)
- 0 to top of R307 : 340VDC. So, minus the 189: a voltage of 151 VDC! I don't get it
- OP301, left side: 1.1VDC across terminals
- R315, R320, R321, R318 : 0VDC across
- Q301 : BE ~1.0VDC , BC ~0.9VDC
- D301, D304 : 0VDC across
Who can help me diagnose?
Cheers,
Christof.
The obvious first issue was a slightly swollen main capa (C301), which confirmed leakage when unsoldered. Replaced it, but PSU still not delivering.
I see no obvious damage to any component.
Find attached the circuit diagram.
Since I am not at all into analog PS design, I can't find what's going wrong.
My main suspects are the OP301 and Q301 ... but any advise on how to identify/confirm would be helpfull.
I measured some voltages (with 230VAC connected, no load connected) and can measure more if needed.
Note: I cannot accurately measure below 5mV, so 0 could be anuthing between 0 and 5mVDC
- output 5VD: 0VDC
- output DET: 0.1VDC
- across C301 : 335-345 VDC (as net fluctuates)
- IC301 (TOP 266EG):
- V 4.9VDC
- D ~340VDC
- C 0VDC
- X 0VDC
- F & S 0VDC (obviusly, since reference)
- directly across R307, R308, R309 I measure each time 90-92VDC, BUT strangely (checked 5 times), when measuring from 0V(IC301-S/F) to intermediate connections I get:
- 0 to IC301.V : 4.9VDC
- 0 to R309-R308 : 96VDC (consistent with above)
- 0 to R308-R307 : 189VDC (consistent with above)
- 0 to top of R307 : 340VDC. So, minus the 189: a voltage of 151 VDC! I don't get it
- OP301, left side: 1.1VDC across terminals
- R315, R320, R321, R318 : 0VDC across
- Q301 : BE ~1.0VDC , BC ~0.9VDC
- D301, D304 : 0VDC across
Who can help me diagnose?
Cheers,
Christof.
Attachments
-
859.2 KB Views: 13