Onkyo receiver loses preset stations

[Thymeclock]

I have an Onkyo TX-38 stereo receiver. When it is turned off for any
length of time it loses all the stations I have preset. I recall having
this happen once before; I took it to a repair shop who changed a
battery in it. Now I'd like to do that for myself if possible - however, I
searched the circuit boards extensively but could find nothing that
resembled a battery. Any idea as to how to fix this?

[vtech]

Very common problem. It is actually a backup capacitor which acts like a battery to keep about 2.5V supplied to the PLL controller/ processor IC

In your case it is going to be... capacitor C712 on the tuner section. Go back to the tuner section and locate C712 close to the 42 pin IC(TC9147BP) which is rated at .047 Farad (not microfarad) /5 volts. It is also known as a "super" cap. Depending on the manufacturer of the cap used, it is normaly the size of a round button( & don't be suprised if it shows fluid leakage on top or around it)

You need to get a .047 Farad 5 volts "super cap" as the replacement. If space is not the limiting factor you can always use a .22 Farad or higher value instead which will keep the memory longer.

..Used to be called a "gravy repair"