Kenwood KR-8010 cleanup and restoration

Good idea to specify which devices you are proposing to replace. These the drivers for the power amp output? Qe13~Qe16?

Stock devices -
2SA913 - 150V, 1A, 15W, B=150, ft=120MHz
2SC1913 - ditto

Your proposal to replace them with a 4MHz part is probably not a good one. Better choice: Toshiba 2SA1837 / 2SC4793. As long as you don't need a conductive tab, that is.
 
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My bad, thanks for the advice. Yes, this is for those. I also noticed the Zener Diodes D13/D15 were black. I have since removed them and both have tested bad. I will upload some pictures in a bit of them removed and tested. I am looking at the other diodes now. I just removed D11 and it also has failed.

What would you recommend?

Good idea to specify which devices you are proposing to replace. These the drivers for the power amp output? Qe13~Qe16?

Stock devices -
2SA913 - 150V, 1A, 15W, B=150, ft=120MHz
2SC1913 - ditto

Your proposal to replace them with a 4MHz part is probably not a good one.
 
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Can't believe you have that many failed diodes. How are you testing them?

CZ-060 = 6V 1W zener
YZ-140 = 14V 1/2W zener
 
With a Diode tester on a MM. Here are the pics. I believe normal is between 500 and 850?

Thank you very much for your help. Much appreciated I want this thing to be perfect.

I assume that I need the heatpad Echowars? I just looked for T0-220.

I did find these and they look to be pretty good replacements.

2SA1011
http://www.bdent.com/2sa1011-sanyo-audio-power-transistor.html

2SC2344
http://www.bdent.com/2sc2344-sanyo-audio-power-transistor.html

heat marks on pcb
IMG_20150618_132451511sml.jpg

D15
IMG_20150618_143121971sml.jpg

D13
IMG_20150618_143139640sml.jpg

D11
IMG_20150618_144300431sml.jpg

D9
IMG_20150618_145555109sml.jpg

Can't believe you have that many failed diodes. How are you testing them?

CZ-060 = 6V 1W zener
YZ-140 = 14V 1/2W zener
 
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Heatpad? I assume you are referring to a mica insulator...?

If you use a transistor with a metal mounting tab, you may need to insulate the transistor from the heatsink, if the heatsink comes in contact with anything else (and the mounting screw also needs insulation, but I don't see that in the pics you posted, so these devices may not need electrical isolation at all). But the Toshiba devices I listed are fully encapsulated and do not require (and should NOT have) a mica insulator, as an insulator will simply interfere with thermal transfer. But a good heatsink grease (I use Wakefield 120 silicone) is recommended, or a quality thermal pad, like the Bergquist K-10.

http://www.digikey.com/product-detail/en/SPK10-0.006-00-58/BER113-ND/201920
http://www.digikey.com/product-detail/en/120-2/345-1007-ND/340305
 
I meant the metal back (pin4 on some drawings I have seen) and these were just screwed onto the alum heatsink. There were no pads and just a thin smear of grease as expected.

How do you think the transistors I linked will work? I planned on leaving the right channel alone since it runs great and idles very happily at 50mv.

I normally use just a thin smear of hs compound when I install them. A rub between my fingers and it puts a small amount on the pad that you can barely see.

Thanks for the links.

Heatpad? I assume you are referring to a mica insulator...?

If you use a transistor with a metal mounting tab, you may need to insulate the transistor from the heatsink, if the heatsink comes in contact with anything else (and the mounting screw also needs insulation, but I don't see that in the pics you posted, so these devices may not need electrical isolation at all). But the Toshiba devices I listed are fully encapsulated and do not require (and should NOT have) a mica insulator, as an insulator will simply interfere with thermal transfer. But a good heatsink grease (I use Wakefield 120 silicone) is recommended, or a quality thermal pad, like the Bergquist K-10.

http://www.digikey.com/product-detail/en/SPK10-0.006-00-58/BER113-ND/201920
http://www.digikey.com/product-detail/en/120-2/345-1007-ND/340305
 
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I received some of the replacements parts today and put what I had together. Echowars I used the suggest Toshiba PNP/NPN parts you recommended so thank you for the help.

I am now waiting on zener diodes D13/D15 to arrive from nte. Once those are here I am ready to roll. I desoldered and resoldered most of the joints on this board while apart and everything had continuity with a meter and seems to be in decent shape.

IMG_20150625_134203618sml.jpg

IMG_20150625_135300615sml.jpg

IMG_20150625_135338779_HDRsml.jpg

IMG_20150625_135351942_HDRsml.jpg

IMG_20150625_135402005_HDRsml.jpg
 
WOW! Holy Smokes! This receiver never sounded this good. Echowars thank you very much for you help.

I received the diodes around lunch time and hustled through a few other things because I really wanted to hear this receiver. I soldered everything up and then made sure every single pad had continuity with all other pads in the circuit. I also verified no continuity between the transistors and the heat sink or case. This was all perfect. I then walked it through a DBT from 40 watts up to 100 watts and all seemed well. The relay did not kick until the 100watt bulb and I remembered that happened last time as well.

Next, I attached my dummy loads to the unit and set the idle on both channels to 49 and 50mv. I was reading someplace that I should drop these to 25mv? I believe that may have been for my Pioneer SX-1010.

All looked great so I put on some Micca desktop speakers and slowly brought the volume up. All was good and the first song I enjoyed Grateful Dead - Mountains of the Moon.

I then decided it was good. It is now playing Steve Miller - Fly Like An Eagle Vinyl. This made my whole damn week.

I am also beginning to think I need my B&W 604s in my office as I wonder how they would sound with this great old amp.

Now to continue with my restore and replacement of all caps that are not Orange Elna low leakage. I also and considering blue lights and a new set of binding posts. I am wondering how these would work as replacements.

http://www.parts-express.com/parts-express-mini-gold-plated-insulated-5-way-binding-post-set-2-red-2-black--320-3375

IMG_20150702_142046447sml.jpg

IMG_20150702_142057182sml.jpg

IMG_20150702_143618571sml.jpg

IMG_20150702_153028571sml.jpg
 
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I am just finishing up on a total restore on my KR-8010, all new caps, outputs, blue LED lights. Question, my unit is running at about 18 - 20 mV. Is that ok or do I need to adjust up to 50mV. Cheers !
 
I am not certain but since Echowars recommend 50mv I would probably adjust yours upwards.

I am just finishing up on a total restore on my KR-8010, all new caps, outputs, blue LED lights. Question, my unit is running at about 18 - 20 mV. Is that ok or do I need to adjust up to 50mV. Cheers !
 
I recently purchased several speakers and receivers. Amongst them was the KR-8010, clearly the jewel of the purchase. It is in need of a full restoration, and as you stated, there is little online in regards to the restoration of this fine receiver. Thanks for posting your restoration on AK, you can be sure I'll be following your exploits with great interest!
 
I just noticed during rebuild of my KR-8010 that original capacitors C7 and C8, which I removed from X11-1470-10 tone control board, were both 6.3v 330uf. The service manual parts list calls for both caps to be 63v 330uf. I looked at the service manual schematic diagram for clues and it states 6.3v 330uf are used for C7 and C8. So I inspected both removed 6.3v caps and there was no swelling, split insulation or leakage that one would expect from using a 6.3v cap in place of a 63v cap. Also, looking at the low voltages in this area lead me to believe that the 6.3v cap is the correct choice. Not that using a 63v cap in this area would hurt anything, but I couldn't see using it even though I had ordered the larger cap (ugh!). So FYI, error in the KR-8010 service manual.
 
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My SM says Ci7 and Ci8 are 330µf 6.3V. But if your caps look original, then I'd replace with the same.
 
Thanks for checking, and I corrected my error on the cap uf ratings. See attachments for Ci7 and Ci8 ratings in SM parts list versus SM schematic.
 

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Guess I better go look at mine to verify what I put in Ci7 and Ci8. I love this unit so much I need to finish recapping but I just keep using it daily. I now have my B&W 604s on this receiver and they sound great.
 
B&W are some big boys and nice speakers, having the traditional bright British sound. I'll be firing up my KR-8010 today after a complete recap and setting the bias to 50mV last night. Using Realistic Mach Two speakers for testing, can't wait to hear how it sounds":music:
 
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Sweet, I had the wrong size but I had not touched that board yet so I will order a couple new caps. I am in the process of redoing the metal top and wood sides now.

For the wood I am doing 0000 steel wool with Howard restore a finish and will follow with feed and wax.

I am in the process of sanding the metal top and will apply a light coat of rustoleum primer, a light sand and then doing rustoleum hammered dark grey paint. I will upload some pictures of the process. I prefer this unit over my Pioneer SX-1010, Technics SA-600A and Yamaha RX-2700.
 
I wish I had a wood cover on mine! I have done a couple of covers, and also just refinished a McIntosh ML-1C speaker pair that someone coated with latex paint to match the interior of their home. Stripping the paint removed some of the original wood color, so I sanded the entire speaker to remove surface imperfections, prestained with Minwax wood conditioner, restored the original color with Minwax Wood finish in dark walnut and used Minwax Clear Satin Polyurethane to protect the finish without hiding the natural wood appearance. It came out beautiful, and I would recommend these products without hesitation. But, of course, this is your project and you must be happy with it!
 
Sounds like they turned out nice. Minwax seemed to have solid products and good reputation.

I wish I had a wood cover on mine! I have done a couple of covers, and also just refinished a McIntosh ML-1C speaker pair that someone coated with latex paint to match the interior of their home. Stripping the paint removed some of the original wood color, so I sanded the entire speaker to remove surface imperfections, prestained with Minwax wood conditioner, restored the original color with Minwax Wood finish in dark walnut and used Minwax Clear Satin Polyurethane to protect the finish without hiding the natural wood appearance. It came out beautiful, and I would recommend these products without hesitation. But, of course, this is your project and you must be happy with it!
 
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