Model Nine GX / KR9000 Restoration and Recap

[w1jim]

I picked up a nice Kenwood Model Nine GX (the PX or "Audio Club" version of the KR9000) at our recent New England GTG and have begun the fix up.

I will be recapping the amplifier, power supply, tuner, phono, tone and preamp sections. I will not be touching the dolby circuitry since it is obsolete.

The dial and meter lamps will be replaced with LEDs but I'll probably leave the function and speaker lamps alone.

 

[w1jim]

Some disassembly pictures - the front and underside.

 

[w1jim]

First step - the recapping of the power amp and power supply PCB.
I have not replaced the 2 main power supply caps but have replaced all of the others. 2 1uf caps in the audio path have been replaced with poly film caps.

Parts:
2 - 10,000uf / 70v
1 - 2,200uf / 10v
1 - 220uf / 25v
1 - 220uf / 16v
2 - 47uf / 63v
1 - 47uf / 16v (low loss)
2 - 100uf / 25v
3 - 100uf / 16v
6 - 100uf / 10v
2 - 1uf / 63v (replaced with poly film)
1 - 1uf / 50v
2 - 22uf / 35v (low loss)

 

[aileenamegan]

Very interesting. I have both, The NineG and the KR9000G. Your list will be a help for me to service mine...!

 

[EchoWars]

Keep chugging Jim...we're reading.

 

[w1jim]

Next installment is probably a week or so away.
Visiting my daughter in Denver for the week.

Plus I've been trying to determine the best way to pull the tone control PCB without major disassembly - and without having to loosen the dial string.

 

[SicMan]

JIM!
OH man ! gonna leave us hangin '''

Enjoy the time "it's family" and be safe.

John M

 

[w1jim]

A couple of easy boards while I neglect my other duties.

Here's the PCB that controls the Loudness, Mono and dolby calibration.

2 caps total:
1 - 100uf / 25v
1 - 1uf / 50v - replaced with a poly film cap

 

[w1jim]

This one is twice as complex - 4 caps.
It is the PCB that controls the FM muting, meter scale and meter source.

I also had to unwrap the yellow wire that goes to the post in the upper left corner of the PCB (as seen in the picture) ti get it out and accessible.

2 - 47uf / 10v
2 - 22uf / 35v (low loss)

 

[w1jim]

Here's the tone / balance / volume PCB.
It was a bit of a PITA to remove. After loosening all of the screws in it's vicinity (and then some) I found I had to bend one of the metal tags it was screwed to so as to wiggle it out of position.

Parts:
6 - 100uf / 10v
2 - 100uf / 25v
2 - 220uf / 6.3v
2 - 1uf / 50v (low loss) replaced with a poly film
6 - 22uf / 35v (low loss)
6 - 10uf / 25v (low loss)

 

[AudioJoe413]

Nice work, I am watching as I have a wicked thing for the 9's and 11's.

 

[SicMan]

Hey Joe I thought it was the 9600 you had a thing for ??? and the KA --- LOL !!!
Just kidding ...

John M

 

[AudioJoe413]

The 9600 and the seperates are more of a curiosity, the 9's and 11's just oooz beauty. They just have a look. Kinda like this woma....nevermind.

 

[w1jim]

Now - now, there are plenty of beautiful Kenwoods to go around.
I have a very nice KR-9600 (with the metal case, wood would be nice) and a KR-11000G. Tough life!

One goal of my receiver collection is to have representation of TOTL and near TOTL of the 5 major Japanese manufacturers of the day - Pioneer, Sansui, Yamaha, Marantz and Kenwood.

Now back to the to the Nine GX in progress.

I recapped the Tuner / Phono Preamp / Mike Amp board tonight.

Access to the underside was a bit of a challenge. I did it in place because I didn't want to have to deal with the dial cord (though doing it this way you have to be careful not to touch the iron onto the cord - been there).
I did have to move the dolby PCB out of the way to gain access though.

Cap list:

1 - 220uf / 25v
2 - 100uf / 25v
1 - 100uf / 10v
2 - 47uf / 16v
2 - 47uf / 10v
2 - 33uf / 16v
11 - 10uf / 16v
5 - 1uf / 50v (replaced with poly film)
2 - 3.3 / 10v tantalum (replaced with electrolytics)
2 - 4.7uf / 25v low loss
2 - 1uf / 50v low loss (replaced with poly film)
3 - 0.47uf / 50v low loss (replaced with poly film)
1 - 0.22 / 50v low loss (replaced with poly film)

 

[AudioJoe413]

Yup!! There are plenty to go around! Just picked up an 11g today, the cover is very cosmetically challenged, the face is perfect and it has some kind of weird issue that I have to evaluate. But, I got one!!

Still following Jim, the Kenwood seams to be put together well, looks like it makes sense from my seat here.

 

[w1jim]

LEDs

Installed the LEDs for the face / tuning dial.
I'm only illuminating the tuning scale and not the various function indicators (as I did on my KR-11000G).

I wired 2 white / wide-angle LEDs in series in place of each bulb and then put a single 120 ohm / 2 watt resistor in series to limit the current draw. The resistor is inline with the power feed to all of the LEDs.

This mod really makes the face "pop"!

 

[w1jim]

Power switch

I thought I was being a smart-guy when I repaired the lever on the original toggle switch. Problem is that I found the contacts where fused in the "on" position. I tried to open it up and repair it but the guts fell apart on me.

Onto plan B - I took a 3PDT mini toggle switch and a piece of 5/32" brass tubing to extend the lever. Normally I would use a switch with a nut mount but I had this clip in version here so I used that with a little JB Weld to keep it steady.
I put some JB Weld inside the tubing and then crimped it tight.

I found that the original switch had 2 switches in one.
The main contacts and then the small slide switch on top. The small slide switch was "on" when the main power contacts were "off" - probably has something to do with the protection relay.

The original switches power contacts were rated at 5 amps / 125VAC as are the contacts on the replacement switch. I took the liberty of paralleling the contacts on the replacement to double the capacity.
The original .01uf / 250v cap that paralleled the contacts had limited lead length and was bulky so I replaced it with a smaller version I had.

The original toggle switch knob was missing so I used a similar one I had in the parts drawers. A little heatshrink tubing and a touch of silicon sealant to keep the knob in place finished it up.

 

[w1jim]

Getting ready to wrap it up - tweak the amp adjustments and let it run for a while and we'll be ready to put it into service.

 

[aileenamegan]

Really great job and very good description to follow all your steps.:thmbsp:

 

[AudioJoe413]

Nice job Jim, i'm diggin the LED's...very blue and as you said...POP!!