Hello,

Few months ago I got a mint Kenwood KT-917 from eBay.

When it arrived, I hooked it to my amp and turned it on - everything worked flawlessly except for the DDL LED not being lit when a station is tuned.

Since I didn't have a rack that it could accommodate it, I didn't immediately start to use it.

Few days ago, I finally had time to build the rack.

I put the KT-917 in it and I started to listen to some music.

After some time I noticed that the tuner started to be quite warm.
After some three hours the top of its metal case got almost burning hot - when I had a palm of my hand on it, it didn't feel comfortable at all!
I had a sensation of almost being burned.

Even the tips of rotary controls were warm, as was the front glass...

Here is the pic of KT-917's initial placement in my rack:

http://www.kujucev.com/ar/917a.jpg

I figured out that ventilation might not be sufficient, so I increased the space above the tuner like this:

http://www.kujucev.com/ar/917b.jpg

The situation got much better - after few hours the tuner's top surface got quite warm, but not unpleasantly hot.

When I tried it in the open, out of the rack, after few hours it was only lukewarm.

So far I only had slim digital tuners and this is my first monster analog one, so I don't know if this is normal.

It has all this lamps inside and a huge transformer and capacitors that could find a place in some amplifier.

If this is normal, how these things were supposed to be used?
In what kind of rack?

If it should get so warm, why doesn't it have some ventilation holes on the top of its case?

The heat build up is so excessive even in my rack that has all four sides completely open. Shelves are connected only by three threaded iron rods.

Or maybe some aged components inside are over heating?!?

On the other side, the sound that this tuner puts out is awesome, that it is hard to believe that there is something seriously wrong with it.

Thanks in advance,

Aleksandar

PS

I'm sorry because of waisting some space, but I'll put the same question in the Vintage Solid State AK section, in case that some "solid state" people are not visiting this forum.
I really need to know if something is wrong in order to prevent some bigger failure!

Nice tuner. You might want to join the FM Tuner Forum (there are quite a few European members) http://tech.groups.yahoo.com/group/FMtuners/ and ask your question over there. The people on the FM Tuner Forum are very good at answering these questions. My guess is that your power supply is off in some manner. That is really the only place in a solid-state tuner that generates any heat. Also, you can read a bit more about it here: http://www.fmtunerinfo.com/kenwood.html

Kuja,
Most older tuners make a bit of heat but it's created by the dial lamps for the most part. I can't tell other than by what you're saying wether it's normal or not so I would recommend you check and see what lamps are installed in the unit. It's always a possibility someone installed lamps that are higher output than stock. Again, it's very hard to tell over here just looking at the picture but even at that the tuner looks "very" bright. Brighter than what I would expect.

Ron

...Again, it's very hard to tell over here just looking at the picture but even at that the tuner looks "very" bright. Brighter than what I would expect.

Ron,

The lights appear to be too bright only because of the photo - I took it in a dimly lit room. I used long exposure and a tripod.

Few months ago when I opened the case, all the lamps seemed to be OK.

Thanks.

This is most likely a silly question, but the voltage settings on the back of the unit are correct, right? I purchassed an L-07TII from a seller in Hong Kong a while ago and was having exactly the opposite problem....the tuner turned on, but the display lights were very dim and it sounded terrible! Turned out the seller had permanently disabled the rea-panel voltage switch and set it to 220V...so it was barely receiving any power from my 120V line!

Other than that it's hard to say. My L-series gear seems to run a bit on the hot side, but I've never had any significant issues...remember that most electronic gear is more than happy to run at 55 C pretty much indefinitely!

Enjoy that tuner, she's a beauty ;)

Well some kind of reality check is probably in order. There should be a max power or current rating listed at the rear of the tuner. That value should give you a feel for the amount of power consumed. If you could somehow safely measure the amount of AC current being consumed by the tuner you should be a feel if the amount is reasonable or not.

I've had tuner, the Kenwood L-07T II, get warm after an extended period but that was mostly due to the massive metal case, front panel and mechanical construction...the whole unit would conduct heat such that acted like a very large heat sink that kept everything at the same temperature. Not hot but very evenly warm, I'm sure that was normal for the specific model.

A tuner usually on requires a few watts for operations so I think you should continue to investigate this as it's a very desireable tuner and I'm sure you wish it to continue to live a long life :thmbsp:

Lefty

Well, I opened the KT-917 today.

I left it turned on for one hour and then I started touching the components.

The transformer got very warm, but not on the unpleasant side - I can hold my fingers on it indefinitely.

On the other side, there are a couple of heat sinks that got extremely hot - I can not touch them longer than one second. I could seriously burn my fingers on them.

I took many photos and I marked red the heat sinks in question.

The transformer and those heat sinks are the only real sources of heat, everything else runs almost cool.

Here are the pics - what do you think?

http://www.kujucev.com/kt917/04_kt917.jpg

http://www.kujucev.com/kt917/05_kt917.jpg

http://www.kujucev.com/kt917/05a_kt917.jpg

http://www.kujucev.com/kt917/05b_kt917.jpg

http://www.kujucev.com/kt917/06_kt917.jpg

http://www.kujucev.com/kt917/07_kt917.jpg

http://www.kujucev.com/kt917/08_kt917.jpg

http://www.kujucev.com/kt917/09_kt917.jpg

http://www.kujucev.com/kt917/12_kt917.jpg

http://www.kujucev.com/kt917/13_kt917.jpg

Alek,

There's a lot of stuff inside that tuner! If this was mine, I'd get the schematic and take some voltage measurements, particularly around the power supply. Those caps where the vinyl sleeve has slipped down may need to be replaced as well as those with what appears to be corrosion on the bottom (the one next to R3). The brown stuff on the pcb is glue.

As what's his name said above, figure out a way to safely measure the current draw. The panel on the back sholud give you a worst case number and if yours is higher than that, you'll need to check into it right away.

Heh. Make sure it's setup for 220v (I guess) but it would probably have already blown up if set for 120v.

Murray

I would check the bias resistors to the four? transistors attached to the heat sinks. There appers to be two transistors on the botton of the heat sinks. You'll need the schematic for correct bias.

Ron

This tuner needs some ventilation very badly.

If it was mine I would quit worring about "keeping it all original". I'd cut out a rather large hole in the top, leaving about 1" of metal all around, and pop rivet a pc of expanded aluminum from the inside. Then spray it all with a matching paint.

Those caps with the sleeves shrunk way down, that ain't right! Replace those.

The light brown thin stuff by the some of the large caps looks like glue. The thick dark crusty stuff looks like electrolyte leakage.

Whoa! That medium brown stuff dusting some of the components and a few places on the circuit board does not look like regular dust. It looks like smoke residue. And the discoloration on those hot transistors.

Let me put it this way. I would not leave this thing running and leave the room. Or leave it running while a made a milk run.

Do you have a fire extinguisher? Preferably CO2.

Most likely the transistors on those heat sinks are voltage regulators for the power supply. The transistors themselves are discolored from excessive heat and should be replaced. They should not be getting that hot! The caps nearby have the plastic covering shrunk because of heat and should also be replaced. You need to find the source of the overheating condition. Either the input voltage on the regulator transistors is too high, or there is something drawing too much current on the output of the transistors. You are going to need a schematic to troubleshoot this. Check the voltage setting, maybe it's a 100VAC unit or is set to 100VAC.