Restoring a Kenwood KR-9050

[Nemo bit]

I have 2 KR 9050’s and 5 Kr 9600’s. 1 9050 and 1 9600 are nib. I listen to to 9050 all the time,it’s one of my favorites. I will see if I can see what it looks like underneath. I have a G22000. I like the 9050 better. The G22000 has been on a self for years.

I started with a Kenwood and will always have one. I am envious I was.happier than a pig in... well ..you.know. I have also.had several Sansui's albiet all were 9090db vintage and older. I had a Au-D9 which I enjoyed but at the same time when a friend wanted
It I really didn't think about its leaving as a big loss. I don't care for the cosmetics of my G-9700 compared to prior models. I do like the sound very much. I would love to have a big G series
I just think they a end of the real competitive time of the manufacturers. I could also desire a top shelf Mac system. I however realize in my lifetime that will be when I have a herd of moon jumping cattle. I started out with nothing....And I somehow find.I do indeed have most of it left. I may indeed find opportunity to own a big G. I have lots of speakers that would love it.
I always like the 9050 it is a great build and so many things about it make sense where the KR-9600 is a bit of a unicorn unless you have doners. If a model eleven ever is presented, there is another I absolutely love. It's the perfect blend.
My first "big un" was a KR-8010 I had it over 40 years and only sold it last year. It was a solid unwavering piece of equipment. I however always felt it was a bit sterile. I guess I like a bit of risk. It just seems more satisfying. I am kicked back listening to my 9600 turned up at a level most might not relate to. It's a joy to listen to a set of speakers I missed entirely during those raising kids and providing to the best of my ability to take care of responsibilities that were taking all my time, thoughts and sanity. A bit of Pinkfloyd add a dash of Supertramp some SteelyDan along with the tUbes I am well into a inner happy place. I had to call and have a driver sent for my SDA 2 Bs so I am finding Comfort with that ole 9600 making that signal go thru a little set speakers called Ohm 2XO's I think they are the reason New York is on the map. All is right with the world, Think I'm crazy I can see, from now on!

 

[KR7600]

I bought my units a long time ago. I bought several spare powerpacks for the 9600 when they were available. The 9050's were rare back them. I am from New York and went to NYU. We used to go to Tech High Fi in the village and listen and drool over everything.I always liked the ohm products. They are still around in Brooklyn. I have a pair of Ohm A's, 2 pairs of ohm 4's, 2 pairs of ohm 2's and a pair of Ohm G's. They can stll be serviced by Ohm except for A's and F's,call dale harder in ohio.

 

[Nemo bit]

I bought my units a long time ago. I bought several spare powerpacks for the 9600 when they were available. The 9050's were rare back them. I am from New York and went to NYU. We used to go to Tech High Fi in the village and listen and drool over everything.I always liked the ohm products. They are still around in Brooklyn. I have a pair of Ohm A's, 2 pairs of ohm 4's, 2 pairs of ohm 2's and a pair of Ohm G's. They can stll be serviced by Ohm except for A's and F's,call dale harder in ohio.

 

[Nemo bit]

Your ohm 4s how do you utilize them are you using them in a HT environment?
I am using my 2XOs only for 2 channel music. I seem to keep returning to them
And will I expect use until I am able to finish my SDA 2Bs. My space is not small and due to ceiling shape I seem to get a sound signature of a much bigger speaker. It took a lot of trying different locations but they are surprising to say the least. I from the mid seventies have had some pretty (or at least I thought at the time) impressive speakers and am having a hard time accepting these that I can pick up and put almost anywhere do as they seem to. I would like to see a set of 4s and it seems they are for a huge area. I have indeed done some research and they are still building selling and upgrading. I think I was lucky that these are th XO series as it appears to make a significant difference.I am happy that someone is ensuring the big K's will continue to make music for along time.
I am lucky to have a friend who was trouble shooting problems after they were in the hands of consumers and talked to the manufacturers daily. I would not with out that never could have had one.
Jason

 

[KR7600]

I only use the 4's for 2 channel audio. I like my 4's,the more you listen to them,the more I like them.

 

[txturbo]

Well... Back to the restoration of the KR-9050.

Time to deal with the lamps..

The problem with the KR-9050 lamps is that they are basically wrapped in paper and the paper burns holes over time. This is a really poor design in an otherwise excellent receiver. Time for an upgrade...

To do the upgrade all you need is a piece of Lexan or polycarbonate plastic, 6 warm white LED's a few parts for a power supply and a drill press.

I used 4 1N4003 diodes arranged in bridge rectifier format with a 220uf 50V cap across the DC output of the bridge built on a small piece of perf board. This was all done with parts that were lying around, you could probably get by with just a single diode and resistor. The 6 LED's are arranged in series with a 120 ohm 1/4 watt resistor. The supply is connected to the AC section of the power supply that normally supplies the lamp circuit. Once rectified you get clean 23V DC. I used this LED. I put a piece of shrink tube around the perf board and tie wrapped it to a wire bundle under the power amp.

The plastic is drilled out on the end to hold the LED's. The LED's were 5mm so I picked a drill bit slightly larger. I took my time and drilled each one until the LED was flush to it's flange in the hole. I put small holes to hold a tie wrap next to each LED. The LED's are held in place with a tiny bit of clear silicone. The end opposite of the led's has a 45 deg bevel. When the light shines from the LED's it hits the bevel and shines down.

The result looks just like the original incandescent lamps with the pattern of each lamp above the meters and tuning knob.

 

[Verde]

Nice job on the 9050 lights. I think it's great that you are trying to keep the original look with new parts.
Do you think you can swap in led's on a hitachi sr 2004 and keep the original green tint?
Verde

 

[txturbo]

Nice job on the 9050 lights. I think it's great that you are trying to keep the original look with new parts.
Do you think you can swap in led's on a hitachi sr 2004 and keep the original green tint?
Verde

Not sure... I think I am about to get my hands on one so I will know soon.

 

[CrtclEuphony]

you wouldn't happen to have the wiring diagram for the meter lamps under the paper would you? from left to right (or from speaker peak meter to tuner knob)?

 

[txturbo]

I need to check. Maybe best to just take a set of pictures.

Are you making a plastic diffuser?

 

[CrtclEuphony]

I need to check. Maybe best to just take a set of pictures.

Are you making a plastic diffuser?

I'm cleaning up a mess that I've created. I have a 9050 I had rebuilt but neglectied to tell the tech to swap out the old lamps for LEDs. The tech is a member here, so he will remain nameless as none of this is his fault. In any event, I ordered what I thought were the correct LED lamps, isntalled them, but now have lost the signal strength meter, FM lock, and the FM comes in reaaaaal faintly, but it is tunining stations. Just at a really low audible level. So, first things first, I want to make sure i re-wired it correctly. I'm going to order a new set of LEDs from David Wojnarowski that should be correct. The first set I got from ebay.

Lots of rookie mistakes there, but if you had a wiring diagram or pics including the jumper routing on the inside of the paper, it would be greatly appreciated. Also, if you had a template of your lexan bar/lamp holder I would appreciate that as well. The LEDs I installed yesterday all work but I'm worried I did something to the FM section. Any thoughts?

 

[txturbo]

I would temporarily disconnect the new lamps and see if the tuner is working.

I think I do have a template for the diffuser. Let me look.

 

[CrtclEuphony]

Un solder the lamps completely and leave the wires unconnected to see if the FM comes back in?

 

[txturbo]

Let me look at mine when I get home and I will send you a note of exactly what to check.

 

[CrtclEuphony]

thank you sir

 

[txturbo]

OK... I just took a look at the schematic and it looks like the 16V tap on the transformer that powers the lamps also goes to the tuner board.

I would start with simply disconnecting the led's that you installed and see if the problem clears up. I am not sure how you wired up the LED's but the simplest way I could imagine would be to remove one of the wires for the lamps from the power supply board in the back left of the receiver. If you have the service manual take a look at the big schematic on page 19. Find quadrant 2,O. You will see the lamps with one of the legs from the lamps going to pin 7 on the power supply board X000-2040-10.

There are three wires on pin 7 of my receiver:

Green connects to the tuner board, pin 14.

Brown and Blue... I know that one goes to the speaker selector switch and provides power to the speaker selector lamps and the other to the dial lamps. Remove both of them and the lamps should be bypassed.

The lamps are in three pairs wired up in parallel. When you wired the LED's up how did you do it?

In order for me to install the LED's I put in a small circuit to provide DC for the LED's from the 16V AC tap on the transformer. I can't see exactly what I did without further disassembly. I can do it if need be.

I will look for the lexan drawing for the lamps in the morning.

 

[CrtclEuphony]

OK... I just took a look at the schematic and it looks like the 16V tap on the transformer that powers the lamps also goes to the tuner board.

I would start with simply disconnecting the led's that you installed and see if the problem clears up. I am not sure how you wired up the LED's but the simplest way I could imagine would be to remove one of the wires for the lamps from the power supply board in the back left of the receiver. If you have the service manual take a look at the big schematic on page 19. Find quadrant 2,O. You will see the lamps with one of the legs from the lamps going to pin 7 on the power supply board X000-2040-10.

There are three wires on pin 7 of my receiver:

Green connects to the tuner board, pin 14.

Brown and Blue... I know that one goes to the speaker selector switch and provides power to the speaker selector lamps and the other to the dial lamps. Remove both of them and the lamps should be bypassed.

The lamps are in three pairs wired up in parallel. When you wired the LED's up how did you do it?

In order for me to install the LED's I put in a small circuit to provide DC for the LED's from the 16V AC tap on the transformer. I can't see exactly what I did without further disassembly. I can do it if need be.

I will look for the lexan drawing for the lamps in the morning.

1. I wired the LED's the way they came out, in parallel and exactly the same wiring scematic. I tried disconnedcted them but still no tuner- or should I say extremetly muted tuner.
2. I'll have to look deeper at the schematic to understand what you are saying about "pin 7".
3. What do you mean by "I put in a small circuit to provide DC for the LED's from the 16V AC tap on the transformer"? I dont want to hassle you to tear down your reciever, I appreciate the info.


Thank you for the time being

 

[txturbo]

The lamps are incandescent, they have no polarity and run on AC. You replaced them with LED's that are polarized and would typically require a current limiting resistor at a minimum. LED's are still diodes and if you place a diode across your AC line in the wrong way that's also running to the tuner I am not sure what would happen, especially if you did not limit the current. The LED's may have nothing to do with the tuner issue.

What is the part number of the LED you used and can you show a picture of how you wired them up?

On my receiver I created a small circuit to rectify the AC to DC in order to drive the LED's. This prevents the LED's from flickering. The circuit consists of some small diodes, a capacitor and a resistor to limit the current. I have the receiver apart so I could look and give you more details on what I used.

I am sure that I used this and the note on the bag shows what the rectified voltage would be. The 6 LED's are all wired in series with a 120 ohm resistor.

 

[CrtclEuphony]

I definitely rewired them exatly as they were, including the green resistor you see on the left in your last picture. I also reused the black jumpers to wire in parallel. I also discoverd I had some bristol board left from architecture models so I redid the white paper. Bristol board worked well, its about the same thickness and creaseability, but clearly not as good as the lexan for longevity. If I keep it like this with the bristol board, I will eventually redo the blue lexan beneath it. Here are some pics

 

[txturbo]

So if you used the resistor that would limit the current. Since you disconnected the LED's and the problem persisted that's probably not the root cause.

Focusing on the symptoms you have no signal strength, no lock and little to no sound....

With the muting switch off:
As you tune the receiver up and down the dial do you get any movement on the signal strength meter or tuning meter?

With no signal at all is the tuning meter in the center?

Do you get a stereo signal ever?

Does AM work?

If you look at the back of the tuner board you will see connections from the small antenna board on the back of the receiver that go to 15 and 16 on the tuner board. Are thees connections good between the antenna board and the tuner board?
The problem your describing is how my receiver acts without the antenna connected.