Strange! Tested bunch of small value resistors around output transistors and everything is ok, not a single one burned. Also checked main capacitors, and other pair also concerned with power supply rails that have bigger voltage than it should, and seems that excessive amount of voltage is spread around as offset. I wonder what could cause such big offset in outputs and all transistors in main board. What is more strange why this offset voltage protection circuit didn't show by different voltage than 0.6 volts at pin 2, because that is pin intended for that purpose? I even measured differential pair to discover that I don't have 0 volts at both bases and emitter but 3.6V, 3.4V and 4.0V. This offset have all transistors in main board I measured so far. I should have 0 volts at emitter, 0.6 volts at base and 41 volts at collector. For example one output transistor Q711 have this 4.3V at emitter, 46.4V at collector and 4.8 volts at base. That was surprise, since I discovered that there isn't one transistor that matches exact voltages that it should. Then I tested voltages of many components and compared it to that ones in manual. I noticed when I reconnect speakers board without connected headphones and speaker switch board, it also goes to protection. On that board is connected other board that goes to the speaker selector switch and headphones. Tried to check all components on speakers connection board and everything tested ok. What I did notice is the fact when I disconnect connector for speakers board, I don't have flashing letter P on display, and I can normaly operate device such as switching inputs or tuning fm radio stations. Protection state is indicated by flashing red letter "P" on display, and commands are blocked. Only 3 elements are connected to pin 4: resistor R816 22k, capacitor C813 4.7u 50V and diode D903 11E2 and every single one is tested ok. But, what made me confused is the fact, that pin 4 is intended for detection of absence of AC signal, in which case output pin 6 should deactivate speaker relays. Also very small difference is at Pin 3, where I should have 0.8V instead of 0.7V. It should be 1V at pin 4, and 37.1V at pin 6.
Measured voltages are at:Ĭomparing those voltages with that ones stated in service manual, I noticed that they are different only at pins 4 and 6.
SONY AUDIO TUNER FLASHING PROTECT MANUAL
It has 8 pins, and I noticed that my measured voltages are different than those listed in service manual of receiver. Before that it was ok, played ok, and after switching it off, after about 10 days of not using it, tried to switch it on, but, surprisingly, it went to protection.įirst, I measured voltages of protection IC, which in this case is UPC1237HA. I've been trying for two days already to figure out what is going on with this receiver that all from a sudden went to protection mode.
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