Help with repairs on a KT-615 Tuner

[Yodathedog]

I need to attempt minor repairs on my new KT-615 Tuner. Both bulbs are out and the stereo/mono switch won’t lock in the in position. I have the service manual, but it’s useless for a novice like me. Are the bulbs wired in or are they removable from their sockets? Either way is ok, but knowing going in would help simplify things. Also, what is entailed in replacing the mono/stereo switch? I’m ok at soldering, but by no means an expert.

It’s otherwise in excellent condition and I would love to be able to use it with my also newly acquired KA-701 amp.

Any guidance will be greatly appreciated.

 

[hopjohn]

Are the bulbs wired in or are they removable from their sockets?

I'm not singling you out so please don't take offense I've been meaning to say something like this many times and this goes on quite a bit.

These are the type of posts that generally see me not responding. You have the unit there in your possession yet you want someone to answer something you could easily answer yourself with a little examination. If you're going to be willing to do the repair you're gonna have to be willing to get the lid off of it, so why not look it over for yourself? While I do have intimate familiarity with some Kenwood tuners (KT-7500 for example), I and others don't have categorical knowledge of everything Kenwood produced. You helping us goes a very long way in you getting what you want, answers. Also even if you don't have a camera you could provide a link to an image from a google search of interior photos relevant to what you're wanting to know and maybe even point us to a pdf of the service manual so we don't have to spend the time to do that as well. It's what I would have to do to answer your questions, so just as a common courtesy, please help us by being thorough.

Here's what I know without doing anything more than looking at some not so great google photos. You have at least one bulb (lights the meters) in a rubber surround that's almost certainly wired in, and if there is actually another such bulb it will be the same so soldering will be required. The photo is too dark for me to be certain if there is two or not. The bulbs are typically 7.5 to 8v at 250mA to 300mA. My advice would be to wire in sockets so future bulb replacement is a breeze. I've used these from parts express with success that work with wedge base type bulbs that you would use. Those can be had on ebay and through the resident bulb guy dgwojo.

As far as the button , sounds to me like it is really gunked up and wont latch or is just broken. The first step would be cleaning it with DeOxit to see if that cures its ills. If not, and you really must have mono, then find a photograph of it or desolder it from the board and post a photo of it so we can all see what type of replacement you'll need. Pictures really are worth a thousand words on this site.

 

[Yodathedog]

It’s already open and I have already Deoxit-ed the button mechanism and pushed it in and out a couple of hundred times. The problem appears to be in the blue part and not the button on the face. And it’s stuck in mono. After looking at it again, if it needs replacing, it’s going to be beyond my rudimentary skills.

The bulbs are no big deal. I just wanted to know if someone knew if they’re plugged or soldered into their jackets.

 

[hopjohn]

Looks lke a tubbed design, there is no bottom plate for pcb access is there? That kinda stinks.
Edit: Correction, There is a bottom plate shown in the exploded view of the SM.

There is a contradiction in what I'm seeing and what you are saying. The inward position of the switch according to photos is for mono. So if it won't lock inward it's in the out position which is stereo (Auto muting). Maybe you can clarify this.

If DeOxit didnt do the trick then with a few modifications the switch could be bypassed so you'd have stereo regardless of the switch position (assuming you are truly stuck in mono to begin with).

The service manual is here for anyone following along.

If the SM is correct you have two 12V 150mA bulbs in the gray holders that can be replaced iwith wedge based types of the same value. In the white holder there is a smaller 8V 50mA bulb. I'd turn to dgwojo for help with getting these. Again, I'm pretty certain all of these are soldered directly to the bulb through the holders, no sockets.

 

[Yodathedog]

Thanks for pointing out that there are 2 blue bulbs. I had no idea there was a second one until I looked and saw the other one on the far end of the dial. Pics are included.

 

[rickl]

View attachment 1467333
The problem appears to be in the blue part

I'd study how the switch works and what makes it latch. My experience it is something simple that is keeping it from working. You shouldn't need to take it apart or unsolder it. Just study it and you can figure it out.

 

[Yodathedog]

I'd study how the switch works and what makes it latch. My experience it is something simple that is keeping it from working. You shouldn't need to take it apart or unsolder it. Just study it and you can figure it out.

I’ve fiddled with it a bit already and even trying to get it to stay at the in position it’s still in mono, so there may be more to it.

I did order the bulbs, and I'm confident about rudimentary soldering. I considered it a free bonus since what I really wanted was the amp and I paid $200 for both, usually the price of the amp by itself. I won’t be using it much as there really aren’t any decent FM stations around here.

Thanks for all the help. I’ll post a picture when I get the bulbs installed.

 

[hopjohn]

The "in" position of the switch is mono. The "out" position is Auto / Muting or another words stereo with muting on. If you aren't receiving a stereo signal on a known stereo station it very likely has nothing to do with the switch. If the stereo indicator lamp is actually burnt out, it may be receiving stereo but be tough for you to tell OR it might be the tuner is out of alignment so you're receiving only in mono OR both the bulb is burnt out and it's also out of alignment.

You can verify the functionality of the switch in its current position with the power off using your multi-meter using the ohms setting. The left side of the switch should be the left channel, the right side the right channel. Connecting one probe to the middle left leg and one to the front left leg should show a very low reading like 0.2 ohms. The middle right leg and the front right leg should also show a very low reading. The middle left leg and rear left leg should show open or OL (open loop) on most meters, and same with the middle right leg and rear right leg, OL.

 

[Yodathedog]

Don’t have a multi-meter.

 

[Yodathedog]

Here’s a follow up on the tuner. I got new bulbs installed and all are working except the stereo light, which my tiny brain figured out wasn’t working since there’s no stereo signal due to the bum stereo/mono switch being inoperable. I may get that fixed sometime, but for now i’m happy and very pleased with my work.

 

[aileenamegan]

If the switch doesn't work: its broken inside - or at least battered. Not uncommon for these tuners/switches. I have at least still three tuners here (615/815) having the same problem. There is a feeding nose (no idea to explain it better) and a spring for fixing the two positions. After decades of using it this plastic nose will be destroyed mechanically...Bitter reality.

 

[Yodathedog]

If the switch doesn't work: its broken inside - or at least battered. Not uncommon for these tuners/switches. I have at least still three tuners here (615/815) having the same problem. There is a feeding nose (no idea to explain it better) and a spring for fixing the two positions. After decades of using it this plastic nose will be destroyed mechanically...Bitter reality.

That’s my assessment as well. I hope to hook up with a local tech that can help me with this and several other low/medium projects that are beyond my skill set.

 

[Blue Shadow]

Mouser has a switch that could be put in place of that one.

Figure out the electrical requirements
Figure out the pin out/spacing which doesn't need to be absolutely exactly the same as it looks like there is plenty of room on the board and below the switch to get pins connected where they need to be
Figure out a way to mount the new switch so that the plunger will operate it properly.

Find that swtich and intsall with creative engineering if needed but you should be able to find one like it. Mouser would help, contact them send a pic and they can narrow it down I'm sure.