I bought this unit for $10 at the salvation army. I'm just curious as to what might have happened to it. I haven't taken it apart yet, so i'm just going on observation. When turning the unit on, without the surround being on you have no relay clicks, and no sound (with both A and B turned on). If you turn surround on, you hear a relay click and get sound out of the rear/center channels. Pressing/Depressing A will then give a relay click. I wonder if there is a problem with the amp, or the relay? any ideas?
Maybe can clarify the reasons you have different output configurations. I worked for Dolby in London for ten years and cinema processing was an area close to me.
To cut a long story short;
The number of factors and different combinations possible for a fully equipped cinema offering Dolby and / or other protocols to the guest is large to say the least even within the Dolby formats.
For Sony to try to offer a range of home units (recievers or tuner/amps/decoders in this case) was to say the least ambitious .but hey!..........who else can give the public what they think they need.,,,good old Sony
I have looked at this unit and it seems the "amplifier section" is used for various configourations and power output ratings vary depending on the configuration you choose.
Stereo 2 ch L+R is 2 x 75w
Surround requires more channels (centre and mono rear) and of course new signal routing to and from these blocks which of course will draw from the modest power supply.
So 4 channel surround will deliver 4 x 50w.
etc. etc.............what you hear are the relays which are reconfiguring and re - routing the signals.
Basically you cant have all the sections working all the time due to cost /design restraints
So speakers A OR B can be used but not BOTH when in surround mode....where the centre and surround are needed. .you cant have A and B at any time....push both buttons an NEITHER will work ....release one button and there you go.............it saves "letting the smoke out of the box".........which you should never do...........cos they never work without it. :)
Sorry for boring you ...............but I think you will find the unit is working just fine.............you could read the manual but that's not too informative.
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The speaker output connections on this stereo system unit are called RCA...named from the inventing company. Computer speakers use what is called a "mini-plug" and as you've found out, the two are not the same.
I would suggest checking at your local Goodwill or Salvation Army store for an inexpensive pair of speakers with the proper RCA connection you need. Second choice is the local Radio Shack store...tell them you need speakers with RCA type connections and you will also need two RCA to RCA speaker wires to make the connection needed.
You cooked it. Maybe you lucked out and just blew a speaker.
Generally speaking, an amp attempts to protect itself from heat, shorts, overloads and operator exuberance by refusing to turn on or stay on.
Overloads can be from excessive periods of high output or marginally low impedance loading by the speakers; and shorts would be wiring issues or a speaker blowing up.
You should be able to feel if it's hot. WHY is it overheating? Make sure it has sufficient ventilation on all sides and that vent holes are not blocked by dust balls. Ensure the fan (if equipped) is running as designed (some only operate on demand). Clean dust and debris from it.
If the amp comes back on after cooling, you're lucky. They only have so many self-protection cycles in their lives so continuously resetting or cycling their power without addressing the cause can do more harm than good.
If it protects immediately on a cool power up you should disconnect the speaker connections and try it 'naked'. If it comes up then diagnose which lead(s) are shorted. If it does not come up the problem is internal and should be left to an experienced and competent hands-on tech.
Check for loose speaker connections at the speaker as a root cause for intermittent shutdown.
I can see why you're asking for help on this. It almost seem this unit has been 'disappeared' as far as online information is concerned. Even Sony has nothing on it.
I founs some articles and For Sale posts:
"Sony's STR-4800SD receiver was extensively, and positively, reviewed in Stereo magazine's Fall '77 issue. In their introduction, they found the 4800SD bettered its published f.m. sensitivity specs "by a wide margin...it has exceptionally smooth frequency response, very low distortion(especially in the midband), and excellent quieting. No exotic claims are made for the power amp section, either (35 watts/channel,15.4 dBw at 0.2% THD). But our tests indicate much more capability than that, and a distortion of only one-tenth that spec."
The power consumption figure shown in a photo below says "145W", which would be consistent with a 35 watt amplifier.
This can happen. Lightening causes static charge that can be picked up by speaker wires. It is possible ONE of the amplifiers has failed. To check, have the room quiet. Turn on the amp. After 5 to 10 seconds there should be a nice solid 'CLICK' from inside the amp. If there is no click, the unit is in safety mode. You will need a service shop.
You most likely have a short in one of your speaker wires (+ and - are touching somewhere) causing the receiver to enter a protect mode "Click!". Disconnect all speaker wires then connect and test each one at a time to find the culprit. I've seen this happen with speaker wire or a subwoofer cable that is too small of a gauge. Hope that helps.
Receivers like this will incorrectly decode rear channel audio and pass it on to the rear channels as distorted audio. Make sure the source being used really has rear channel information encoded into it. It could have other issues but check this first.
I think you mean the left channel is out but when you use test tone, the sound comes from left and right channels through the right channel speaker. If this is case, the switching IC is malfuncting. Unit needs service