Big Receiver. Big Problems? • 1971 Kenwood KR-6170 • Plus, Magnum Sleuth Antenna Amp Demo

A surprising fix for the dead FM. Vintage Magnum Sleuth antenna amp demo. More capacitor testing and repairs. Guitar input demo. Noisy transistors?
Here are the topics covered and time stamps:
0:00 Introduction
0:12 Recap of Parts 1 & 2
0:48 Let’s Fix The Dead FM
1:45 Magnum Sleuth FM Tunable Antenna Amplifier
5:21 Removing A Bottom Brace
5:29 Removing The Old Filter Caps
5:50 Testing The Old Filter Caps For Capacitance, ESR & Leakage
12:40 Installing New Caps With Adapt-A-Caps
13:36 Using A Terminal Strip to Replace Filter Cap
14:15 Trying The Guitar Input
14:56 I'm Nervous!
17:30 Noisy Transistors?
To see all the videos in this series, please click:
• Kenwood KR-6170
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#kenwood #stereo #stereorepair

[@JNElectrics]

Nice memories vintage radio. 👍🏾

[@sonny5973]

Had that unit send home from Japan in 1972 , got it when i was in Vietnam. Was like Christmas my folks were like whats in all those boxes. 4 speakers and reel to reel , reciver....

[@MODAC]

Your technical skills are exceptional. 👍👍👍

[@FluxCondenser]

Thanks, Dave. I’d trade it all for your skills!

[@6StringPassion.]

They should make a Magnum Sleuth for OTA TV. The "amplified" antennas that are sold at the big box stores are trash.

[@BobWilson84]

How funny, the timer knob is bigger than the tuning AND volume knob. Boy were they proud of that fancy timer :) nice work. I can smell the Elna caps from here.

[@FluxCondenser]

I know! The tuner knob would definitely have benefited from being larger. I can understand why the timer knob is so big, though. It takes a fair amount of strength to turn it, so in that regard it helps. Glad you enjoyed the video. Elna caps? I can’t smell anything after all that contact cleaner I sprayed ;-)

[@SongBill40]

Your video is great! Thanks. I've got a KR-6170. Have had it for over 50 years. Still works and sounds great..... except for brief distortion at Power on and occasional infrequent drops in the L or R chan, quickly resolved by my working one or more of the many push switches on the front panel. More an annoyance than a real problem. Your video informs me these might get resolved by my replacing those five capacitors you removed and replaced. Think I'll order those five filter and output capacitors from Mouser (or Digi-Key) and give it try.

[@FluxCondenser]

Glad to hear. Good luck.

[@nickcoleman9085]

Enjoyed your video on kr6170 interested if you have had problems with channels dropping out. I have an issue with mine with the right channel dropping out and seems to come back to the input selector , I clean selector and it works OK for a while then begins to play up again. I'm starting to suspect a dry solder joint somewhere just not sure where to start. Would like to hear your thoughts and suggestions . Thanks

[@darthbubba866]

Your guitar buddies will hate the Kenwood - it doesn't distort enough like their guitar amps do. :-) But seriously, last time I heard that rushing noise it was a loose base leg on an input transistor. The base leg was barely attached to the inside of the transistor body, not a bad solder joint on the circuit board. Also I've heard that noise come from impedance mismatches which seems unlikely in this instance. The Kenwood's guitar input is spec'ed for 20mV at 30Kohms and I suspect that your oscillator is 600ohms or less at output.

[@FluxCondenser]

Thanks, Darth. Yeah, I warned them that this’ll be a “clean” sounding amp. Noisy, but clean ;-) The transistor types on the guitar preamp are notoriously noisy and I’ve secured some more-modern replacements, so it’ll be interesting to see how much that makes a difference. I’ll get more into this in the next episode.

[@darthbubba866]

@@FluxCondenser The 2SC458 transistor used in the guitar input is reportedly famous for its high noise level, why in the world did Kenwood pick it for a +20dB guitar preamp? I just took another look at the schematic; the Kenwood is literally filled with the 2SC458s. Better brew a barrel of coffee 'cuz you're gonna be doing a lot of soldering :-(

[@FluxCondenser]

Exactly, right. But, I’m going to take a surgical approach with this and just address enough of the transistors to get this to “good enough” operating condition. The reverb will need to some attention, too. So far, those are the only circuits that seem to be bothersomely noisy, so hopefully I can just get away with that. As I said in the video, I don’t want to get into a full recap on this thing so I certainly don’t want to go full re-trans, either.

[@darthbubba866]

@@FluxCondenser "I don’t want to get into a full recap on this thing so I certainly don’t want to go full re-trans, either." Heresy! The OCD Audiophiles Association will be hearing about this!

[@FluxCondenser]

Oh, man. Yeah, I used to be like that. Now, I just wanna have some fun. For something I’ll need to be absolutely dependable day-to-day, sure, but otherwise there’s just too much I gear I wanna play with for a while, then put on a shelf and move on to something else interesting. I’ve got more fully restored radios and Hifi gear than I could ever possibly listen to regularly. Don’t get me wrong, I still enjoy doing full restorations, but sometimes “good enough” is good enough.

[@R.AudioElectronics]

I don’t know what the levels are but maybe it’s the noise floor if at maximum level

[@FluxCondenser]

Yes, but seems unnaturally high and with more high frequency content than I would expect. Will have to see if transistor replacement improves things. Stay tuned.

[@R.AudioElectronics]

@@FluxCondenser yes looking forward to it. I did notice transistor 2sc-458 listed for this unit has a tendency for leakage,noise and static so if these are in the audio paths might be a good place to look. Good luck! I’ll be watching for what you find

[@gillanland]

Effectiveness of Magnum Sleuth would've been apparent if it had a bypass, otherwize the test didn't look convincing!

[@reneneron2971]

Pick me!