Hello,
I am not experienced in repairing Amps but I am willing to spend time and learn. I am trying to repair a Receiver/Amplifier & looking for some help with understanding the power supply schematic (Attached).
Current state:
- Amber/Orange standby light comes on.
- S5V is present (TF91 is on)
- No other lower voltages are present (D+7, +-12, +-45 vcc)
Once Power is plugged in the system goes in standby state (Ember/Orange light comes on). When I press on/off:
- Ember/Orange light goes out
- AMP_vcc_on (BN65 pin 14) goes to about 3.2V
- Power_HI goes to about 3.2 V
- after about 15 seconds, Ember/Orange standby light comes back on.
What I have done thus far:
- All transformers checked OK for continuity
- replaced bad caps on high voltage side (C901/C930 - 270uF 250V)
My understanding is that when power is turned on after standby state, PC2 and PC1 should pull low, turning on Q902 and Q903 in turn providing vcc for IC93 and IC92. I observed that indeed, PC1 and PC2 goes low but I did not see vcc for either IC (93 or 92). Can someone please tell me which of the three switching transformers (TFP91, TFP92, TFP93) should be on during standby state.
Looking to understand that aside from S5V, what other voltage(s) should be present in standby state; Should +_ 12 and 7vd be present during standby?
Any help is highly appreciated.
Cheers