Help with Sony STR-6055 Problems

Picked up a free Sony STR 6055 today. Cosmetically good but no sound until you turn the volume ALL the way then you get a very small amount of understandable music. Ive cleaned all pots and inside of unit...any suggestions??:scratch2:

I picked up a later (but also highly respected) sony receiver today as well—the STR-V6-and am experiencing what may well be similar issues. Perhaps we can work together, and with the help of more knowledgeable minds resolve (or at least diagnose) our issues.

With volume "maxxed out" I get some listenable audio ... but a low volume. I'm guessing it's putting out well below a watt per channel. I'm thinking we could have the same basic issue because my unit is much more powerful (118WPC as opposed to your 40WPC, IIRC) so my amp is able to take a super-low signal and make it listenable whereas you described yours as merely perceptible.

I'm no electrical engineer but I'm thinking we have a problem in the preamp stage that is failing to bring our signal up to proper levels for the main amp (or perhaps even attenuating it.)

It may be of note that on my unit the signal meters BARELY budge at full volume on mine.

I did find something that could be of significance on what I think may be the preamp board (on the right, with the tuner hardware) that looks like a TINY ceramic fuse, when I pulled it out of it's holder it didn't seem change the performance any (removing other fuses would kill a channel, or all output completely). The little tiny fuse-looking-thing had no writing on it, and showed no conductivity whatsoever on my cheap multimeter.

Not sure it's supposed to be a fuse, since the holder was a bit awkward to remove it from, and I bent the clips in such a way that it doesn't want to stay back in now... If it helps more knowledgeable minds this unit is perhaps 6 millimeters long, white ceramic cylinder with metallic end caps. It's about 2 millimeters in diameter. It's home on the circuit board was labeled "T-CON SW".

Do you guys think our issue is something to do with the preamp not "amping" (or worse) ... also, any guesses on this little fuse-like doohickey and what it may be replaced with?

I don't want to hijack your thread... let me know if you think I'm off-topic, so I can move it.

I'm far from an expert in these area's, but it would be a good idea to see if you get anything from the headphones jack. Also is it the same with all inputs? This will be more info for the experts here...

Fuses could be bad, sound like no conductivity says bad fuse. There is probably another issue if fuses are blown.

I'm sure others will chime in soon.

Good to see im not alone. I get a very very quiet signal at full volume probably quieter than you due to my lack of power. Have not tried the headphone jack but will do. Thanks for joining me on this.

The problem has been verified on FM, AM and AUX inputs. (I don't have a working record player to try "phono"

Headphone jack sounds a bit louder when at full volume, but not really "loud."

FWIW, when I patch my headphones to the tape out jacks the volume is very low... significantly below line level output of say my ipod when it's in it's dock.

Also, this little fuse-like-unit is tiny (like just a hair larger than the dancing banana icon)... it's really weird to me that there is no label indicating the specs for the "fuse" on the holder or the "fuse" itself. Also the holder does not lend it'self to replacement, I had to pry metal tabs away from the unit to get it out, and they don't spring back in.

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Now for some hopefully unrelated info: channels cut out at low volumes, it's the right channel on speakers and left on headphones (but yes, they are wired correctly, as verified by toggling the "balance" knob.

My deoxit work is so far not complete, I have only done the volume pot, none of the jacks, switches or other pots.

Now for the weird part: when a channel is cutting out (at low volume) it comes back if I increase the treble control. (The tone does not seem to be distorted when the cannel is cutting out)

Again, just trying to get more info for when those in the know actually chime in.

echase55. I would definately continue on the cleaning track on all pots, jacks, switches, etc. Take a pictue or two of the questionable "doohicky) and where it is inserted in the unit.
If the phones jack is not much better, it's probably not the power amp portion. If you can get ahold of a service manual and or schematics, that may help you along as well.

craigs28, I have an str6055 as well, but I can't help you a whole lot on it. Mine was working when I got it other than 1 pot needed some deoxit, I don't have a manual for it yet.

May sound simple, but verify the knobs and switches are in the correct position. A knob could have been put on the unit in the wrong position. Other than that, you're gonna have to wait for someone wiser than I.

Oh, the str 6055 is a nice sounding unit when you get it rolling.

Goodluck!

Thanks for all the advice...im going to clean it again more thoroughly and check all fuses etc...not a big deal considering i got it for free

I have a bit of new info, and a new theory on this.

I think my higher volume levels were due to more efficient speakers. On a hunch I jumpered the leads on the speakers right into the headphone output from my ipod, and the volume was the same as what was coming out of the STR-V6 at max volume.

So, I'm thinking the amplifier is not amplifying.

Does this seem logical?

Another tidbit of information: after powering on the amp there is no sound whatsoever, until the relay in the amplifier section goes "click" then I get the headphone-power output.

I thought that that relay was just there to wait until the caps were all charged up before putting sound out (my newly acquired STR6045 does not click, and it's scratchy for a second or three while it powers up). But my theory on this relay simply being a warmup timer may be no good, as it sometimes takes longer to click.

Could this be the protection circuit popping? Where do I go from here?

I have a schematic, but it's like learning to read all over again.

Thanks for any pointers. This monster receiver will be my pride and joy if I can ever get it going.

Voltage regulator for pre-amp

I think you may want to check the voltage going to your pre-amp section. If I remember correctly, there is a small power transistor to regulate the voltahe to your pre-amplifier section. I f there are not voltahe there, that will give the same condition as you had mentioned. Give that a try.

Thank you for the reply. I solved the issue but forgot to document it in this thread.

After much time tracing voltage levels, etc I finally put the tape monitor switch into the correct position and everything was much better. (Except my ego, which let out the magic smoke after this incident)