KR-8010 - 2nd Take

[Super Noob]

Was so impressed with my KR-8010 that I am going to do another. Will likely be sold on Barter Town once it is completed.

Will update the post in the upcoming weeks.

HopJohn... Kenwood Guru = what is your opinion of this model. It is a beast.

 

[Super Noob]

Unit Arrive Updates to Follow.

 

[BigElCat]

I had one of those...luv'd it.

Mine had the factory side handles.

Massive.

 

[Super Noob]

Power Switch - Contacts Switched To Unused Side and TRAIC Modification Complete.

Prior To Disassembly

In Process

Finished - Works Flawlessly

 

[Super Noob]

Power Supply:
Before

After:

Replaced Caps & Relay:

 

[Super Noob]

AMP Boards:

Before:

After:

Parts:

Trim Resistors (Bais) Replaced with Bourns 25 Turn Sealed VRs.

 

[Super Noob]

Outputs:

Outputs Pulled, Cleaned, Re-Pasted with Wakefield Thermal Paste.

 

[Super Noob]

PreAmp Board:
Before

After:

 

[Super Noob]

Front End Boards / Tone Controls:
Before

After:

Also DeOxit All The Controls / Contacts.

 

[Super Noob]

Tuner Board:
Before

After:

Parts:

Spent 2 hours cleaning the old flux off the circuit side with 90% Alcohol.

 

[Super Noob]

Filter Caps:
Upsized the caps from 18000uF to 22000uF 105 C, 80V Snap In Chemicon. The solder tab direct replacement is not available, so I elected to remove the tabs, install them on new caps, stuffed them in the old cap cans, and reinstalled using the original bracket. Turned out sweet.

Install with 2.2 uF Stacked Film

 

[Super Noob]

Adjustment:
The left channel offset was roughly 40 mV.
The right channel offset was less than 5mV.

40mV is okay... but not up to my expectations. I elected to pull out the 1st different pair:

Replaced A921s replaced with A992s perfectly matched.

Offset Improved:
Right

Left:

Bias Dialed Up To 50mV:

 

[Super Noob]

LEDs:

 

[Super Noob]

Here are finished pics:

The case shell paint was dull. Hit it with hammer black finish. Turned out really good.

Used all 105 C high quality Nichicon Caps (mostly KA series) and WIMA films.

106 New Caps
2 New VR Sealed Trim Resistors
2 Gain Match SA992 Transistors
New Relay
9 New LEDs

Here is a list = hope it helps out someone in the future.

https://drive.google.com/file/d/1vR64nceIHzzPqHsHg76uJI3KkVbQqB_-/view?usp=drive_open

Sounds as expected clear and strong. Will run in for a few weeks and list on barter town.

 

[Super Noob]

I had one of those...luv'd it.

Mine had the factory side handles.

Massive.

I was so impressed with my 1st one... that I wanted to do another.

 

[AlpacaLips]

Super Noob, I can't tell you how much I appreciate this thread and the parts list you posted. Yesterday I picked up a Kenwood KR-8010 and Nakamichi CR-2A tape deck, both with mint cases and in their original pristine cartons, for US$150 (and the seller threw in a TEAC CX-210 deck and a pair of mediocre speakers for free). My hope is to use the KR-8010 with my similar vintage Kenwood KD-5033F turntable ($15 at Goodwill; yes, I'm a proud cheapskate). Here's the problem with the KR-8010:
--Stereo and several source indicator lights burned out
--The FM and at least one of the tape inputs, at best, go out continually, either right or left channels; right now I can't get FM to function at all. Strangely, AM seems unaffected. I haven't tested the Phono or Aux inputs yet.

I saw your KR-8010 on eBay and my jaw dropped. First at the price, and then even more at the sheer beauty of the thing. So needless to say, in addition to obviously getting this thing working right, I want to upgrade the indicator lights to LED as well. (Dang that blue dial is gorgeous.) However, I'm a noob at this (I've done recapping and other minor troubleshooting of Commodore computers, but no audio equipment), so I'm hoping you can answer a few questions:

1. Do you have any suggestions for troubleshooting the FM issues?
2. I'm a little unclear on how the LEDs works in the old system. Did you have to add any resistors or anything or do they just pop inline where the bulbs were? I noticed that they weren't in your parts list; do you remember the specs on the LEDs you used for the meters, input selection indicators, and dial?
3. You mentioned Wakefield thermal paste but your link went to Silver Fox. I notice the Wakefield is much more expensive on Amazon (https://www.amazon.com/WAKEFIELD-SOLUTIONS-120-5-THERMAL-GREASE/dp/B005T5H2TS/) Is it worth it?
4. I understand why the caps need to be replaced, but what's the basis for the relay and VR replacements?

Some aspects of this are pretty intimidating, especially your filter cap treatment and your channel offset adjustments are 100% over my head.

Just for funzies I'll attach a pic of the 30 years of dust I blew out of this thing. Again, thanks so much for this post. The parts list combined with the before and after photos will be a huge help.

 

[Super Noob]

It sounds like someone messed up your alignment on the tuner... both my KR-8010 had good functioning tuners. I don’t have formal alignment tools for tuners.

I have only had to do a course alignment once on a SX-750. Got good help here and was successful (Watthour). I am not your guy for helping there. Be careful and read tuning posts for a few hours. Non metal tweakers hand tools and mark original positions. These adjustments are amazingly sensitive and if you don’t know what you are doing things might get worse.

I generally just replace the electro caps on tuners.... never transistors.

Am concerned my image hosting for my projects will be lost soon as I used googleplus.

Wakefield 120 is my choice... non conductive paste is what most of the knowledgeable folks use and recommend.

KR-8010 is a under radar. I basically just recap these units - transistors retained. If your basis is out you can replace 1st order pairs on the amp board if you match the transistors.

I have read a lot about LEDs. I make custom LEDs, but 95% of the time I use these.

ALITOVE 20pcs 5mm 12V White LED...
https://www.amazon.com/dp/B06XJZCP71?ref=ppx_pop_mob_ap_share

ALITOVE 20pcs 3mm 12V White LED... https://www.amazon.com/dp/B06XJZWMJM?ref=ppx_pop_mob_ap_share

Yorkim 194 LED Bulbs Xenon White... https://www.amazon.com/dp/B00JRE38EA?ref=ppx_pop_mob_ap_share

LAOMAO (Blue) 1 Pack (20 Bulbs) 5mm 12V... https://www.amazon.com/dp/B00H9874XM?ref=ppx_pop_mob_ap_share

cciyu 28mm-31mm 5050 3SMD LED... https://www.amazon.com/dp/B013OYTOUK?ref=ppx_pop_mob_ap_share

I typically scuff the indicator lights and flatten tops with cheap nail files. Use a single blue LED on each side for the dial illumination. The indicators I believe were 3mm white LEDs. The meters was a single 194.

All these bulbs work fine with AC or DC in the 8V range. You just have to customize them to fit / work in most cases.

You can keep VRs and relay if you like... relays wear out so I am always proactive here.

VRs same here... sealed VRs are the way to go. I have found these can be a good source for noise (my Sansui 800) and old ones can even go open or become inconsistent - just proactive here as well.

Good amount of deOxit on those control pots. I routine with deOxit and flush / finish with Faderlube.

The cost on rebuilding is labor... that is me so I like include these items.

Weak point on this receiver is the power switch contacts welding in on position.

Good luck.

 

[Super Noob]

https://audiokarma.org/forums/index.php?threads/project-kr-8010.840113/

My keeper...

 

[AlpacaLips]

[Q UOTE="Super Noob, post: 12623690, member: 202953"]It sounds like someone messed up your alignment on the tuner....[/QUOTE]

Thanks for the LED info. I’ll be sure to print this thread and download the higher resolution images and parts list before they disappear.

About the tuner alignment: like I said I know very little about this, but I think I didn’t clearly describe the symptoms. It sounds just as I would expect if there corrosion in the balance knob potentiometer. It’s scratchy when there’s sound, it cuts in and out instantly and for no reason, and does so independently for the left and right ears. Occasionally after some fiddling around with it both right and left work fine on FM and the sound quality seems ok to me. What makes me think it isn’t the balance pot is that (a) AM is fine and (b) it seems that turning the tuning knob has an effect on it. I haven’t made sufficient observations to see if the frequency indicator needle is pointing to the right place when I can hear a broadcast.

Here’s what I’m thinking I’ll do:

1. More thorough general cleaning, while looking for bad traces, broken solder points, leaking caps, etc.
2. Deoxit on pots
3. Further testing with other inputs to see what the tape, phono, and aux do
4. Replace tuner board caps and then test FM again
5. Replace all other caps, VRs, and relay as you did.
6. If the FM is still wacky then hire a pro. It sounds like a good way to for a noob to screw things up.

One other question about the power switch: I get why rebuilding the power switch and reversing the contacts to get a fresh surface would have some value. I am new to the Triac mod though. Is the purpose of this is to insert a relay circuit for the purpose of subjecting the switch to lower voltages?

 

[Super Noob]

Yes.. Triac mod will do the switching at the Triac. (eliminates the arc relating to the high voltage).

Plenty of links going through it... if you want to skip, you could reverse to the unused contacts = they are brand new.

My main recommendation is always to get a good desolder gun = that is the main secret that is not clearly publicized. It makes these projects 100% doable and you will not mess up traces / pads. If you paid someone to rebuilds I do = it would be clearly something like $500-$1000 so invest that saving in tools.

I am as NOOB as it gets.... but I can read, am persistent, not bad with mechanical solutions, have the right tools, & have the right mindset.

You can do this.

BTW = build a DBT. (don't die)

This is the tester I built (HD sourced).

I am excited about your new journey and am hopeful for a positive outcome / experience.