I hosed my KR-7400 lamps, need some opinions..

T

themdg

New Member
Hi There:

I recently bought a Kenwood KR-7400. In good condition, and sounding good. I bought a service manual for it, but am pretty new to electronics like this. It's mostly Greek to me but I'm learning.

Two of the bulbs behind the tuner bar were out, and I thought that would be a good place to start.

Pulled out a bulb, which I had to cut off (soldered on). Bought something that I thought was comparable, a same-sized 12V bulb from radioshack. I tried touching the wires to the new bulb and it burned really dim. After 2 or 3 seconds all the bulbs in the front went out at once. I don't think I burned them all out...but maybe I did.

So, two questions. Anyone know why they all went out? Did I wreck one of the other components that controlls the lamps? Happy to poke around with my multimeter. Just trying to make sense of the manual to see where.

Also, how do I research what bulbs to use when I do get them working again? I'd like to repent and start doing this right.

Here is a shot of the inside of the unit with my blunders pointed out. The other two lamps are examples. There are 3 more that I haven't pointed out. All 5 are not working any longer. A larger version of the image here: http://themdg.org/pics/posts/7400LampsBig.JPG

7400Lamps.JPG




Any advise?
 
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A 12V bulb would be expected to looks pretty dim at 8V. As far all them going out, I'd say it's a fair bet that you shorted the wires.
 
Thanks EchoWars. I'll poke around with my multimeter tonight. By Shorted the wires, you mean some of the wires are currently touching each other right? Or would shorting the wires cause some damage...and something besides the lamps needs to be replaced.

I'll check for some 8V lamps today too.
 
themdg said:
Thanks EchoWars. I'll poke around with my multimeter tonight. By Shorted the wires, you mean some of the wires are currently touching each other right? Or would shorting the wires cause some damage...and something besides the lamps needs to be replaced.
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themdg said:
I tried touching the wires to the new bulb and it burned really dim. After 2 or 3 seconds all the bulbs in the front went out at once. I don't think I burned them all out...but maybe I did.
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Yes, you probably did.
I'll check for some 8V lamps today too.
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8V lamps are hard to come by. Are these 'fuse-type' lamps, or wedge lamps? AK member Dgwojo sells both.
 
Bump

I'd like to bump this...I got one of these KR-7400's from GW the other day and am having lamp issues too.
I plugged it in at the store and it had a couple dead lamps, got it home and opened it up and cleaned it out and now only one bulb lights, what the hell?
I guess I need to search the forum for similar threads, or go straight to the man "dgwojo", but here goes anyway...
How do I ID the bulbs rating, how are the removed and how are they re-installed ( plugged in, soldered?) and should average Joe man about the house on a GW type budget attempt this? I tried to fix a Yamaha RX-350 lamp issue and failed, so I'd like to better my batting average.:bash::bash:
Appreciate any help, will shoot "dgwojo" a note...Thanks.
 
These lamps have a rubber type boot they are encased in, I don't know if they are removable and reusable, or if I'll have to do some surgery on them. I doubt they sell these anywhere. Anyone dealt with these before?

lamps005.jpg
 
Don't lose the rubber boot! Those bulbs will pull out of the rubber part, and any new bulbs you buy will get threaded back in. The larger bulb likely is 8 volt, .3 amp. The bulbs for the larger ones likely won't be exactly the same, but I'll bet dgwojo can fix you up with some that will sit in the boot just fine. They will have leads attached. Service manual should say what rating the lamps are.
 
Hey Kevin...
so the bulbs should slide out of the boots with a little coercing, or are they actually threaded in?
.3 amps...what's that in milliamps?
I wish I had a manual for reference.
 
On the KR-4600 I had for a spell, the bulbs were not threaded into the boots.
0.3A = 300mA
 
If they are like my KR-3090, the rubber boot slides down(towards the bottom of your picture, lets say), and the bulbs will have a little pair of wires sticking out the bottom. The boot basically protects the leads from touching each other or other parts in the unit. I butchered some RS bulbs into place because I couldn't find the right ones locally, but if I had to do it again I would search for the proper bulbs. I think there was also a separate fuse for the bulbs in my receiver, so you might want to check whatever fuses you can find.

Good luck!
 
Thanks all, the dial pointer light is nagging me also, it worked at the store before I bought it, got it home and nuttin. That one looks like an entirely different animal.
 
Do you have a picture of this dial pointer light you speak of? I may have a working one lying around.
 
Heres what I diid...

trotp3 said:
These lamps have a rubber type boot they are encased in, I don't know if they are removable and reusable, or if I'll have to do some surgery on them. I doubt they sell these anywhere. Anyone dealt with these before?

lamps005.jpg
Click to expand...

Got a KR 5400 this summer off the dump. Always wanted one of this series. Would love the KR 7400 but beggers cant be choosers. Mine has the same as pictured above. Went to the better Radio Shack in Kingston NY. They had sockets for the #47 plug in bulb. Measured the voltage at 8 volts too. Bought the 6.3 and 12 volt bulbs. I had three bulbs out and replaced them with the sockets and the pop out bulbs:D Now it they burn out I can replace them easily. Used the 12 volt bulbs.

I did not look where the wires went as my mod worked. If the Kenwood is like a Pionneer though it may have fuses for the lights under the chassis. Blew out fuses on a SX 727 once--shorted the wires by accident.

Got two more Kenwoods from the dump. A KR 7200 and a very dirty KR 5200. These take a #47 6.3 volt bulb. Both work. Been a Pioneer fan but always like the Kenwoods. You will like the sound of the 7400. Been pleased with them. The earlier KR 7200 sounds great.

These receivers were built well. The KR-5200 was covered with dirt. It almost did not make the trip home. This poor soul was covered in dirt. Given up for dead by its previous owner. Put it on the bench on Labor Day. It fired up. "Hey, your supposed to be dead." Quarter inch of dirt inside. Very noisy controls with no dial lights. The Radio Shack type 47 bulb fit perfectly--6.3 volts. Cleaned the controls and blew out the dust and dirt today. It looks like it spent some time in the weather. Had a cold solder joint around the protection relay. Think I got that solved today. My 7200 may have the same issue. May be a problem on this series.

Good luck with KR 7400. My 5400 cousin is living in my shop system. Sounds great. After some more testing, the KR 5200 is going to my sleeping quarters. It will replace a Sony STR 518 receiver. Nothing wrong with it but its too new--1991? for my tastes. Enjoy!

Eric:music:
 
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Most of the Kenwoods I've had with the rubber booted bulbs slide out with a little coaxing. The easiest way to accomplish a relamp is to PM dgwojo for the proper bulbs with leads attached. You will cut the original bulb leads and, after mounting the new bulb into the boot, resolder the new bulb leads to the same wires. Dgwojo has the really nice green bulb condoms, also. It gives off a good color, IMO.

An example:
IMG_0046.jpg
 
a.d. said:
Do you have a picture of this dial pointer light you speak of? I may have a working one lying around.
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"a.d."
I haven't really disassembled it to get a good look at it yet, when I do and if I need one, I'll shoot you a PM or something, thanks.:deal:
 
+1 on dgwojo lamps. He attached leads to some wedge lamps for a Sansui G-3000 I had awhile back. They were a snug fit in the original rubber boots, but worked great with a little coaxing.
 
mfhale said:
+1 on dgwojo lamps. He attached leads to some wedge lamps for a Sansui G-3000 I had awhile back. They were a snug fit in the original rubber boots, but worked great with a little coaxing.
Click to expand...

Just got an order into "dgwojo". I'm wondering if a lil' spritz of silicone will help with the bulb an boot coaxing?
 
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