I bought this receiver about 30 years ago and it has been doing quite fine all this time.
Recently one problem appeared: the Radio forgets its presets when power-off.
I've found a post in this forum about a somewhat similar problem related to a 5-10 years younger AV model that has got a CR2025 battery inside.
I've been searching in the STR-GX40 service manual and I have not been able to find a battery symbol on the schematic diagrams.
Question: Would anybody have an idea how this receiver is storing presets (what technology is used? ), on which of the many PCBs inside is this stored and maybe which component would be defective?
Recently one problem appeared: the Radio forgets its presets when power-off.
I've found a post in this forum about a somewhat similar problem related to a 5-10 years younger AV model that has got a CR2025 battery inside.
I've been searching in the STR-GX40 service manual and I have not been able to find a battery symbol on the schematic diagrams.
Question: Would anybody have an idea how this receiver is storing presets (what technology is used? ), on which of the many PCBs inside is this stored and maybe which component would be defective?
I believe the data is retained within the microprocessor and that its "battery" is a "double layer capacitor," C303 a 0.22F. It's on page 14, along the bottom side of IC301.
Those low voltage memory capacitors do go bad after a while.
Replace it with a new one of a similar uF and DCV rating.
And that really is 0.22F, or 220,000 uF.
Replace it with a new one of a similar uF and DCV rating.
And that really is 0.22F, or 220,000 uF.
Found the component. Thanks a lot for the help !!
Some additional information:
It's on page 14 of the PDF, which is page 23 of the printed document. It's on the display board, close to the Tape monitor & standby LEDs
Voltage is 5.5v and it seems to be a supercapacitor.
I also see R309 being a 100 Ohm resistor in series, I'm assuming that this resistor is limiting the charging current of a fully discharged battery to 50mA (generating 1/4W in the resistor). This might allow to replace it with higher capacity, however there is no need since 0.22F caps are still available today.
Some additional information:
It's on page 14 of the PDF, which is page 23 of the printed document. It's on the display board, close to the Tape monitor & standby LEDs
Voltage is 5.5v and it seems to be a supercapacitor.
I also see R309 being a 100 Ohm resistor in series, I'm assuming that this resistor is limiting the charging current of a fully discharged battery to 50mA (generating 1/4W in the resistor). This might allow to replace it with higher capacity, however there is no need since 0.22F caps are still available today.
Replaced the component. The Receiver is in good working order again.
For info of people preparing a similar intervention in the future: The original 0.22F supercap was 11mm diameter, 4/10 inch pin spacing and form factor was H-type.
It was defective indeed: didn't hold any voltage after being charged.
I didn't want to wait for spare part delivery so I mounted a 4.0F 5.5v supercap on the bottom of the display board. Plenty of room there, this 4.0F is about 25mm diameter.
Also took the time to clean the display glass -task long overdue, but only possible with display board removed- and clean up the ON/OFF switch.
I was overall very impressed by the build quality and ease of maintenance of this receiver.
I'm very grateful for your help- especially in locating the component.
For info of people preparing a similar intervention in the future: The original 0.22F supercap was 11mm diameter, 4/10 inch pin spacing and form factor was H-type.
It was defective indeed: didn't hold any voltage after being charged.
I didn't want to wait for spare part delivery so I mounted a 4.0F 5.5v supercap on the bottom of the display board. Plenty of room there, this 4.0F is about 25mm diameter.
Also took the time to clean the display glass -task long overdue, but only possible with display board removed- and clean up the ON/OFF switch.
I was overall very impressed by the build quality and ease of maintenance of this receiver.
I'm very grateful for your help- especially in locating the component.