Need schematic for STA 2380 digital synthesizer receiver

Question edited for clarity.

Help in the link and also specialist forums

https://www.google.com/search?q=realistic+sta-2500+stereo+receiver+service+manual

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First thing to check is the speaker. Switch them to be sure it is not the speaker. The unit was made in 1987. The capacitors that you are talking about are mounted to the main board. There are more than one. It does not appear that you are very versed in electronic repair and this could be a disaster to attempt to repair the unit. It involves soldering and attention to detail. You will have to remove the main board and all associated items that are in the way. Realistic STA 2380 Service Manual Analog Alley Manuals

All radios hum when they don't know the words. On the real side of things though, there are parts in that unit that change AC to DC and there are parts that suppress the hum.
The service manual is here: http://www.analogalley.com/osccart/product_info.php?currency=JPY&products_id=1124
If you don't know how to solder, I would not download this. You are looking at bad diodes or capacitors.

Where the power cord plugs into the unit look for a red slide switch. One side will say 220 and the other will say 120. Use a finger nail to change the switch to match your local power voltage.

Try MFG website, or email their customer service, or try
manualslib.com

Hi,
Did you ever find the schematics? I am also troubleshooting my STA 3900.

set the channel preset number first. Then tune to the frequency. Then press the green button to store. Repeat for the next station.

Try disconnecting all the speakers and see if the volume goes up without shutting down (watch the vu meter on the front) if it goes all the way up without dropping, you will need to check your speakers. If the speakers are drawing too much current then the system will go into shutdown(protection mode)could just be a bad speaker. Secondly try blowing out the receiver with canned air and removing anything that would obstruct ventilation.(ie; another device sitting on top of it or in a cabinet where it can not breathe.

It won't have "iPod" functionality but it can be played through the receiver.

Any audio device that has a headphone output can be adapted to feed an RCA cable pair for standard stereo to any audio device with a standard RCA input (except one labeled "PHONO"). Get a cable like the one described here: http://www.monoprice.com/products/product.asp?c_id=102&cp_id=10218&cs_id=1021804&p_id=665&seq=1&format=2
and connect it into any available analog input EXCEPT one labeled "Phono".