"Vintage" receiver

[buckeye56]

Hi. My old Technics SA 205 receiver is super hot underneath on the left side (me facing the front of the unit). It's like this if I listen to the radio, play CD, etc.The right side is cold. Only two bookshelf Polk speakers are connected, a turntable, and a DVD player, but obvs I only use one device or just the radio, at a time. The vents are on the top and there's nothing blocking them, not even a shelf above. The receiver sits on a table. Oh, and when I lean into it, I can "smell" the heat.

So what's causing this, and is it going to blow up or something? I thought if I put some kind of wire/mesh riser underneath it may help, but if the vents are all on the top, then it seems pointless.

As always, thanks!

 

[nj pheonix]

Sounds like bias is set too hot.
No way of really knowing without opening up and checking.

 

[buckeye56]

Sounds like bias is set too hot.
No way of really knowing without opening up and checking.

What's the bias, and even if I open it up, what would I be looking at and looking for?

 

[nj pheonix]

I'd suggest getting it to someone that knows.
Without understanding you can easily make a small issue a big problem.
To answer you question.
The transistors in the output section are set to an operating point where they conduct ( or don't).
There's a specified value in the service manual ( generally measured across an emitter resistor which sets the operating point.
A manual and a meter are a bare minimum ( maybe mini gripper test leads) to attempt this.
Sometimes you have to do a little digging ( diassembly to get to the pot and or the test point.
I misadustment can cause the transistors to self destruct ( sometimes taking other things out with them.)

 

[the skipper]

what phoenix says. This isn't like taking TV tubes to Radio Shack to test. You need equipment and some knowledge to poke around in there.

 

[OMGCat!]

Is it a new issue that's popped up? Some units will have hot spots in various locations where components dissipate heat.
Either way, if it's concerning to you I'd recommend taking it to a repair shop for a look. They'll be able to tell you if it's an issue or not.

 

[buckeye56]

I'd suggest getting it to someone that knows.
Without understanding you can easily make a small issue a big problem.
To answer you question.
The transistors in the output section are set to an operating point where they conduct ( or don't).
There's a specified value in the service manual ( generally measured across an emitter resistor which sets the operating point.
A manual and a meter are a bare minimum ( maybe mini gripper test leads) to attempt this.
Sometimes you have to do a little digging ( diassembly to get to the pot and or the test point.
I misadustment can cause the transistors to self destruct ( sometimes taking other things out with them.)

Thank you.

 

[buckeye56]

Is it a new issue that's popped up? Some units will have hot spots in various locations where components dissipate heat.
Either way, if it's concerning to you I'd recommend taking it to a repair shop for a look. They'll be able to tell you if it's an issue or not.

Nah, not new.. Just fee like it's not really supposed to do this, as I have no memory of how it operated 25 years ago to compare it to, lol/