Light Transformer Buzz in Sony TA-1080

[ArthurTut]

I recently picked up a Sony TA-1080 at a good price. I did not have an opportunity to test it before buying it. It appears in excellent condition. It is quite clean for a 59+ year-old unit in all details including the wooden case.
Whenever I buy a vintage unit like this, I take a lot of time inspecting it before I ever attempt to hook it up to speakers. I am still examining it.
All the components look original. It's also fairly clean inside for a unit this old, and it doesn't appear that anyone has done any work in it.
Then, I noticed some things about the power transformer.
(1) The power transformer was not tightly mounted down. It rocked on the frame when I felt it with my fingers. So, I removed the five screws that hold the mount down so I could look under it. Two of the four screws that hold the power transformer down on the mount were completely out and laying loose under the mount. I picked up the screws and put them back in tightly, and tightened all four screws securing the power transformer to the mount, and then screwed the mount back down. Although I tightened the power transformer down as much as possible, it still has a very slight wiggle to it; not like at first when two of the screws were out, but just a little movement. But, it can't be screwed down tighter.
(2) I noticed the power transformer cover has a small dent on one of the top corners. This dent being there is odd because I don't see how anything could have impacted the cover to the power transformer unless someone was inside here. But other than this dent, and maybe the fact that screws were out underneath, it doesn't look like anyone was here. See the picture of the dent.
(3) Then I noticed the voltage selector was set on 100v. I wonder how long anyone was operating it in the U.S. on this setting. It is impossible to know, but I immediately changed it to 117V.
(4) I hooked the unit up to dim bulb tester and turned it on. The bulb in the power indicator on the unit appears to be burned out, but the bulb in the "safety" indicator lights up. There is nothing unusual about the dim bulb test; the bulb lit up briefly, then faded down to no light. I turned the unit on and off a few times, and I don't know if this unit has a "relay," but I assume it does, because I can hear that secondary click whenever it is turned on.
(5) There is a very faint hum or buzz coming from the power transformer. It is audible, but I have to lean in to really hear it, and it probably wouldn't be audible with the cover on the unit. I am sure that's not a great sign, as the power transformer probably should be silent, but I don't know if it means the power transformer is ruined. It might still work okay, I don't know.
I am going to keep examining it and I will try some more testing, but if anyone has any knowledgeable opinions about the issues I am describing, please comment here.
Thank you!

 

[Ray66]

I worked on a Sony receiver earlier this year also with a transformer hum problem. Recap of the power supply took care of it in my case.

Thread 'Sony STR-7065A Transformer Hum'

Feb 12, 2026

My current restoration project is a Sony STR-7065A. Aside from the usual problems (dirty contacts/pots, burnt out lamps, etc.), it has a very noticeable hum coming from the transformer. It's moderate when idling, but pushing it to max power into dummy loads gets it buzzing really loud. To be clear, this is a 60Hz vibration and not something coming through the speakers. I've read posts saying the cause is likely loose transformer laminations, but as you can see from the photo Sony has this transformer in a can. There are 4 screws holding it to the chassis. I'll try pulling it out to see if...

• Ray66
• hum sony transformer
• Replies: 6
• Forum: DIY

• 

 

[avionic]

There is a very faint hum or buzz coming from the power transformer. It is audible, but I have to lean in to really hear it,

I wouldn't lose any sleep over it.

 

[Ray66]

Yes, 'slight' might be normal and therefore Avionic's advice is good. In my case the hum was very loud, like you could hear it across the room loud. There was definitely an issue needing to be addressed in that case.

 

[Julian12345]

I just finished restoring mine. It had no sound. A bad transistor in the pre amp supply, so no pre amp. Also had two open capacitors on driver board of left channel and many other caps tested bad ESR. Most carbon comp resistors I checked were way out of spec. I decided to replace all carbon comp resistors. The output transistors two tested weak. Replaced. My relay was also a bit stuffed and I mechanically sorted it... cleaned and tweaked its contacts so now it doesnt go limp on one channel. This one took many hours but mine was quite tired. Set symmetrical clipping and idle current. I think I did 30mA

It is a very nice sounding amp. Very low noise floor. No hum in speakers at all. Good detail. Wide mids.

Please be aware the lights on the front are NOT normal. They run off the secondary of the transformer at around 80v ... I installed 110v LEDs off ebay and it works ok.

I also dont think your transformer is a problem. Mine is audible slightly but not through speakers

 

[ArthurTut]

I am still working on my Sony TA-1080, but I had a problem with a control knob that took me several days to solve. I wanted to remove the knobs to remove the faceplate, to clean the faceplate and the plate behind it, and to clean the potentiometers with Fader Lube. However, one of the knobs (the Left Bass Knob) would not come off. The slot on the set screw was damaged. I could not remove the set screw with a tiny flat head screwdriver like the others. I could not see how it was damaged because it was not possible to see clearly into the hole where the set screw goes in. I spent days struggling with tiny screw divers, and tiny left hand drill bits, trying to turn the set screw. I started with a #47 left hand drill bit, and then went to a #44 left hand drill bit. I only used a power drill with the #47 bit for about 30 seconds, but stopped because I didn't trust using power. The rest of the time, I just used the left hand drill bits manually. Today, finally, I got the set screw to turn a little bit and the knob came off. Then I used a tiny screw driver and a small right hand drill bit to manually rotate the set screw clockwise until it fell into the center hole where it can drop out. The set screw came out with no damage whatsoever to the knob or the threads inside it. I discovered it is a 4-40 set screw, and the hardware store has them, so I bought several new ones. Here is a picture of the damaged set screw that came out. It is photographed next to the edge of the blade from a razor knife. You can see how hollowed out the damaged set screw became from my use of the drill bits on it to get it to move out enough to get the knob off. I thought I would never get that set screw to move or the knob off. I am so happy I was successful.