Sony TA-1150

[quotidien]

Hi, new member here, I just picked up a SONY TA-1150, the amplifier looks and sounds amazing, I had to part with my audio lab 8000a, but no regrets. The Sony was advertised as fully working but it has some issues that I thought that you could help me with.

1. There is a loud thump when powering on, independent of volume position on both speakers that lasts only for a split second, it visibly moves the woofers of my speakers, I can avoid it by closing the speakers when powering up
2. When the low filter is pressed the left channel of the amplifier stops working (almost completely),
3. In phono 1 or phono 2 input if the volume is above 5 (without any signal in) there is lot of hissing (kind like white noise) from both speakers, this may be normal due to the phono line having a lot of gain, it did not happen to my audio lab or Sansui but they are more modern amplifiers. When I listen to an LP the hissing is not audible as it is masked by the signal. When you press the phono 1 or phono 2 buttons there is a lot of scratching heard by the speakers (this I kind of consider normal but I just wanted to mention it to give full info).

So the questions that I have is what is normal behaviour and what is not, also how important the issue with the thump or the low filter, if it is something that you think affects the amplifier as a whole then I can try to service it (total newbie but I know how to use a multimeter and solder).

thanks a lot

 

[62vauxhall]

In 2018 I bought a TA1150 advertised on Craigslist that was supposedly working. I was unable to audition but bought it anyway. I soon learned that it did work but not very well. One problem was a noise when switching on the power and a "thump" when switching it off.

That problem was only resolved some years later and after extensive parts replacement. I cannot say exactly what replacement parts eliminated that sound but I suspect it was replacing the output transistors and driver transistors. That was done more than once because the combinations of certain modern driver transistors and certain modern output transistors were a major factor in stablity as not oscillating.

From personal experience, I can say that the traces on the PC board are delicate and extreme care needs to be taken when unsoldering/resoldering. Traces lift easily and solder pads can detatch easily. With my example, I had to fabricate several jumpers.

I spent time with the amplifier off and on since I've owned it which as mentioned was from 2018. The most intense period was from April 26 to July 23 of this year which was finally when the amplifier performed properly. That saga, which is not the only one, was documented in a different forum and was 249 posts in length.

A Sony TA1150 was the very first brand new amplifer I ever bought which was in 1973. That was why I spent all the time and money on replacement parts. It would be embarassing to disclose how much I have invested in this amplifier so I won't.

But at least I can say that now, it is at least as good as new.

There may be some insights for you about a TA1150 within that last, somewhat lengthy thread.

Adjusting an old bias pot did some damage and I am unsure how to proceed

The unit is a Sony TA1150 integrated that I've had since 2018. It was unwell when I bought it but it did power up and it did pass signal. I did not use it per se, just hooked up for the odd listen over a couple of years then there came a time when it stopped amplifying. I learned some...

www.diyaudio.com

 

[quotidien]

Thanks for the info, I started seeing the thread, I am sure your amplifier is as good as new and you have learned a lot of things along the way. Do you think that now, after all this effort, the sound of your amplifier when it is playing, it is better? My question is because the amplifier that I got seems to be playing very nicely, I mean I am using it now and sounds very good to my ears. So I am debating if I should go down changing things to eliminate a thump when switching on, considering that I am a novice.
Also, if it is not a lot of trouble, could you do me a favor and switch on to phono 1 or 2 input in your TA1150 and volume 6 and above, do you hear hissing?

 

[62vauxhall]

Thanks for the info, I started seeing the thread, I am sure your amplifier is as good as new and you have learned a lot of things along the way. Do you think that now, after all this effort, the sound of your amplifier when it is playing, it is better? My question is because the amplifier that I got seems to be playing very nicely, I mean I am using it now and sounds very good to my ears. So I am debating if I should go down changing things to eliminate a thump when switching on, considering that I am a novice.
Also, if it is not a lot of trouble, could you do me a favor and switch on to phono 1 or 2 input in your TA1150 and volume 6 and above, do you hear hissing?

Bear in mind that it was 50 years ago when I first acquired a TA1150 and my accoustic memory of that time is weak. What I can say is that it souded damn good and did impress my friends.

After I replaced the power supply capacitors which was early on with this used TA1150, I thought the turn on / turn off noise was lessened and at that point and I was prepared to live with it. There have been other amps that crossed my path which exibited turn on / turn off sounds even when new so in those cases it was the nature of the beast. Although I was fairly sure my TA1150 from 1973 did not produce those sounds, I was not positive. When I reached that point in the restoration process, my intention was to leave well enough alone because other than that, the amplifier was working properly I thought.

If it were not for the subsequent issues, I would not have gone farther.

One of the rudimentary checks I do with amplifiers is turning the amplifier up full when switched to Phono In just to see how much residual noise is procuced. The TA1150 I now have, in it's current state, produces next to none. With the volume control at 6, there is none what so ever and as mentioned, must be at full up before any is detected. That sound can be described as a hiss albeit a slight hiss.

If you have not done so, you may want to experiment yourself with either a turntable connected or shorting plugs installed in the Phono Inputs. It's possible that with the Phono In jacks open, it is amplifying something it's picking up to audibility as the volume control is adjust higher.

I am not a rabid proponent of re-capping and only do so when all else fails. And with my minimal diagnostic abilities, I can reach that point fairly fast. My thought that all the electrolytics are old in this particular amplifier and as long as I do the job correctly, replacing them won't hurt anything and could possibly solve my problem.

My example looked not to have had an easy life. As I got deeper into things, I saw there was evidence of previous transistor replacement work having been done.

During past repair projects to other amplifiers I was advised that Japanese transistors (I think Sony in particular was cited) got failure prone as they aged and there were some original transistors in the TA1150's ouput stage. Having been told that, it made me suspicious and created the urge to replace them all. That may or may not have been necessary and as previously stated, getting the right mix was a chore.

 

[Moving Ahead]

If I remember right there is something in the service manual about a slow start -caps and transistor, to avoid turn on thump. No relay.

Use shorting plug and connect table.