Awe man! Sorry about that! Tuner alignment requires some specialized equipment that most folks don't have (I'm missing some of it myself) and my methods combine workarounds and a substitution to get the job done. Perhaps I'll cover it one day when I have all the proper equipment. Thanks for hanging in there!

Hi, With regard to the Triac circuit, I followed the guide posted in AudioKarma: audiokarma.org/forums/index.php?threads/is-your-unobtainium-power-switch-worth-5-and-an-hour-or-so-of-your-time.504673/page-2#post-6897970

Hi, Happy I was able to inspire you! I totally get it about having too many projects though.. You should go for it!

It did take a little bit to shoot, especially because I has to take a break from it so I didn't chuck it across the shop! :-)

Hi, Glad I was able to inspire you! The KR-4070 will drive efficient speakers quite well and should sound really nice. Sorry that I'm lacking in content... My real job keeps me pretty busy. That said, I am working on some other projects and have one in the can that I need to post.

Hi, Glad you found it helpful! I do hope to find the time to do more of these. Your KR-5010 looks nice! Love the styling. Reminds me of Luxman styling. If you plan to go through it, the settings procedure is going to be different. You can find the service manual here: www.hifiengine.com/manual_library/kenwood/kr-5010.shtml The info is free, you just need to setup an account. This will help you with disassembly, and is a must for the alignment procedures. One thing to note is that the power amp section of this receiver does not use discreet components. It uses an SDK Darlington integrated circuit for the power output section. This is typical for receivers from this era. While they sound and perform great, the ICs themselves are near impossible to find if they go bad. So don't push it too hard. :-) The flickering is likely due to a dirty power switch as the general illumination is not typically run through relays. A good cleaning of the pots and switches is always the 1st order of business when reviving and old receiver. Have fun!

@@vintageaudioowl1538 Thank you. This unit seems to be somewhat scarce. Can't find any advertising material for it. I think it's about 1979-81 vintage. I have downloaded the manual and the schematic from Hifiengine. and, there are only two adjustments shown in the service manual, one for Offset voltage which I did, and the other for Power meter, which requires a dummy load. I don't have any provision for a dummy load so I didn't perform that adjustment. And I tried to check for voltage on speaker outputs, and registered just a few millivolts. Since this is a direct coupled receiver, maybe there are no more adjustments to do? I don't know. It does have two relays, I think they are for speakers and the other for audio. I did clean and lube the pots, inspected for burnt components, tried to look for cold solder joints, but probably don't have proper magnification to see them. And so far now, It performs well, with no flickering lights now on startup. Sounds good, so I think I'll leave it alone for now.

@@mantolaman That sounds about right. The STK ICs don't have any adjustment typically. A few mV on the speaker terminals is totally acceptable. Wouldn't worry too much about the meter adjustments, it's basically cosmetic and probably not too far off. Sounds like you found a survivor! Enjoy it!

Glad it was helpful!

@@vintageaudioowl1538 Please one question about the power on Switch. What kind of triac did you use? You have a small drawing for me? Sorry for my english. Best regards from germany. Rainer

Hi, I followed a circuit found on Audiokarma. I've provided the link below: audiokarma.org/forums/index.php?threads/is-your-unobtainium-power-switch-worth-5-and-an-hour-or-so-of-your-time.504673/page-2#post-6897970

Hi, Thanks for the kind words. You're very close! the output devices I used were the NJW0302G and the NJW0281G. I actually had to look at my Mouser invoice because the receiver has long since been sold. They're 150w devices so they're just a tad bit overkill... :-)

Hi there. I'm assuming you measured the caps in circuit, otherwise you were already half way to replacing them! :-) Did you test them for both capacitance and ESR? (Equivalent Series Resistance) Here's the thing with electrolytic caps. The electrolytic material dries up over time from general use, thermal cycling, and age which can cause them to change value or even short in extremes instances. But the greater risk is when they begin to pass DC between circuits where they're put there to block it. This is where ESR comes into play. Recapping an old receiver (40+ years in the case of this one) is relatively cheap insurance against eminent future failure. Sonically speaking, you can improve the sound (ever so slightly) by using better caps in the audio path. This is especially true for low value caps (2uf or below) where you can replace them with film type caps. So that's my rational in a nutshell. I'm not saying that this has to be done if the unit is working well, but it's really just a matter of how long you would like to keep it working well. Pending any other failures, a recap will afford you another 30 years of great vintage sound from your beloved receiver. Hope this helps.

Sorry! With all my babbling I forgot to answer your question regarding the phono preamps. I went after this upgrade primarily because one of the stock preamps failed. I saw this as an opportunity to upgrade to a newer, low noise component. If you listen mostly to vinyl, this might be a good upgrade to perform. It's not too expensive and fairly easy to do if you work in stuff like this. As I mentioned in the video though, I would recommend purchasing the pined version of the opamp as opposed to the flat pack version that I used. It will save you time and frustration!

Haha! yeah, there are a few in there. Truth be told, they weren't all bad but they're cheap enough to replace if you're doing it yourself.

Hi, So the op-amp I used is an OPA604 made by TI (Texas Instruments) you can order them from Mouser or Digikey. Good luck finding the 8-PDIP package version of this device though. Everywhere I look they're out of stock and tagged as an obsolete part. The 8-SOIC package versions are available everywhere and can be had at around $3.00 The adaptor is a BrownDog 111002 TA7136 Upgrade adapter. I ordered mine from Cimarron Technology and at the time, it was $7.90/adapter. Never done a tuner string and I hope I never have to. 🙂 Doesn't look fun! Good luck!

Hi. Well that depends on a lot of factors like what's wrong with the unit, and what the repair shop's hourly rate is. I probably did more work on this unit than your average shop would have; but that's because I love doing this sort of stuff and I don't charge my self any labor! Additionally, this thing was exceptionally broken and most repair shops that are trying to make a profit would have probably turned this one away.

Hi, For the output transistors, I used: 2 - www.mouser.com/ProductDetail/863-NJW0302G 2 - www.mouser.com/ProductDetail/863-NJW0281G If you find yourself needing to replace the output devices and you use these, you will have to drill and tap the heat sink to accommodate them. With regard to troubleshooting, start with the easy stuff: Check to see if you have DC voltage on the speaker jacks. Volume down all the way, set your selector to Aux, remove any input sources and then turn on the receiver to "Speakers A". You should measure close to 0 volts. You'll typically see 50-100mVDC. If that's good, then you might just have a dirty switch. Hook some known good speakers to the "Speaker A" jacks, connect a source to the L&R Aux inputs, set your selector to Aux, and monitor the output. If one of the channels is out or low, try playing with the mode selector and speaker selector knobs and see if audio comes back. Check the balance pot, volume pot, and tape monitor switches too. Dirty switches and pot often present themselves as more serious problem then they are. If that doesn't get it, start checking voltages in the pre-amp and output amp sections. At this point, you'll want to down load a service manual so you can compare your readings. I would also recommend tracing the audio signal from the output stage back to the pre-amp and tone circuitry all the way back to the input to see where it gets lost. Good luck!

Thank you for getting back to me. I'm located in New York. If I can just get away with just basic service that would be fine but I would definitely be open to any suggestions that you may offer.

@@adamfalcon I'd be happy to help you out but I'm on the other side of the country unfortunately. Freight to and from CA + labor might exceed the value of the receiver. I hope you can find someone local. They're great little units.

Hi, Yeah sorry I didn't record the alignment procedure. I was already time consuming enough without filming it and the vid was already over an hour! The "T" meter is the tuning meter on the face of the KR-4070 that tells you when the station is Tuned in and centered for the maximum reception and fidelity.

Hi, Troubleshooting tuner problems would be tough without a signal generator to inject RF and IF as well as a scope and/or "sniffer" to pick up the signal and see where you're losing it. You'll also need the service manual with good schematics and receiver alignment procedures.

Hi Robert, I wouldn't recommend just replacing Q1-8 as a shotgun approach as these are balanced pairs. If your DC offset looks good on the speaker terminals but you still have no sound, its time to do some signal tracing with your scope. feed a tone or a music source in the aux jacks move you selector to aux (make sure tape monitor is off) Start at the 5 wire connector going into the audio board; pins 1 (blue) and 5 (yellow) specifically as these feed the preamp signal into the volume control. If you're good there, follow the signal through the amp board until you lose it. If you don't have signal at those wires, your issue is in the preamp (tuner board). Where ever the signal gets lost, check for cold or broken solder joints use a chopstick to apply pressure to the board in that area to see if your signal comes back. If it's not a solder problem, check voltages around the active devices (transistors and ICs and such) to give you clues. If voltages are weird or not there, don't assume the device is bad. Check the components in the power supply and the supply paths. I hope this helps. Tim

@@vintageaudioowl1538 Thanks for your reply. I actually managed to get it repaired last weekend. I located some NOS 2275s, found a pair that matched up nicely. Problem solved. Works and sounds great especially with the new NJW0281/NJW0302 outputs and 1220/2690 drivers. Seems to have substantially more power. I may try the triac mod on that ticking time bomb power switch you did in your vid. Thanks again. Great vid. Hope you have the time to do more. Will keep an eye out.

That's awesome! Glad you got it working. My real job has been keeping me pretty busy but I've got a couple vids in the can and I'm currently working on a Nikko NA-2090. So many projects, so little time! :-)

@@vintageaudioowl1538 That looks like a nice amp. I'm a big fan of the Alphas. Highly underrated.

Hi, If you're carful, you can bend the shaft back to where it's fairly straight. It will never be perfect but I think you could get pretty close. Just little bits at a time and don't be in a hurry. I've done it to a Pioneer SX636 that I worked and it's darn near bang on.

Hi. The 2 fuses on either side of the faceplate are actually the display lamps. They're known as "Fuse Style" lamps due their form factor. You'll want to replace those to restore your tuning rail illumination. The burning/crackling sound you describe does indeed sound unsettling. Do you hear this without any speakers connected? Can you hear anything through the headphone jack? Do you measure any DC voltage on the speaker jacks when the volume is set to 0 and there's no input? There are 2 actual fuses located on the power supply board that should blow if excessive current is being drawn as long as they haven't been replaced with over rated fuses. You may want to check those too. A dirty mode selector switch can also cause strange behavior and noises to come through the speakers and will even lead to a no sound situation if it's really dirty. So check all that easy stuff first.

Thanks for the kind words and suggestion to do a more end-end style video. I try to balance detail and length so the vid doesn't get too long, as an hour long video is already a pretty big commitment. That said, I will definitely take your request into consideration for future videos.

@@vintageaudioowl1538 ok thanks!

Hi, With regard to the Triac circuit, I followed the guide posted in AudioKarma: audiokarma.org/forums/index.php?threads/is-your-unobtainium-power-switch-worth-5-and-an-hour-or-so-of-your-time.504673/page-2#post-6897970 I don't have BOM for all the caps as there were several that I had on hand. That said, BOMs are a risky thing anyway because circuit boards will often undergo design revisions where the component values and positions may change. It's best to have a svc manual and the unit in front of you so you can verify components before you place an order.

Hi, I would begin to look in the Pre-Amp portion of the output circuit. There are a handful of Japanese small signal transistors in that area that are known to be problematic in this regard.

I was poking around on it recently and I have 90mv and 45mv dc offset I set the bias to 15mv I still haven't figured out why it's popping in the right channel yet I'm almost thinking I should recap the unit and see if it goes away

Also I bypassed the power switch to take that out of the equation

As I mentioned earlier, it's probably a small signal transistor in the pre-amp circuit. I would feed a tone (1k @150mv) in the aux inputs and follow the signal path with a scope or an old school signal tracer until you find where the noise is being picked up. Good chance that the transistor just before that point in the chain will be your culprit. Good luck!

Hi, Sorry, I'm not a repair shop and I unfortunately don't have the time to work on outside equipment. most of the stuff I work on I've purchased broken, repair and sell to fund the hobby.

Good point! I guess I was kinda cheating... Lol

@@vintageaudioowl1538 LOL!

Hi, I'll sometimes take a crack at newer stuff, especially if it's something I'm fond of. Plate amps are usually class D with a switching power supply and schematics are a little harder to find. If you like the speaker and dropped some coin on it, a new plate amp might not be a bad idea. Parts Express has some universal ones you could adapt if your stock one is no longer available.

@@vintageaudioowl1538 Thanks for the reply. I was actually referred to you and your channel by my brother. He told me that he purchased the 4070 you restored in this video. It looks great and I am a bit jealous. I have had the sub for about 8 years now. I really like the size and output, but it wasn't terribly expensive. Based on your advice, I am now debating on buying a Dayton Audio plate amp, or a new sub. The amp is $109 and I can get the same sub now for $199. Thanks again and I will keep you in mind should I need some advice, or repair work.

Well, I opened it up, found a perfectly good fuse and all the caps look okay. None of the capacitors look domed or leaky. I tried a new sub cable, but it didn't do anything. I hooked the sub up through the speaker line inputs and voila, bass. Perhaps the receiver's sub out is bad? I still can't find any schematics. Any suggestions?

Well if you don't have a scope or an AC voltmeter, you can validate your sub output with another amp or receiver. Just route the sub out of your receiver in question to and aux input of another amp and see if you get a signal to amplify. Keep in mind that if it's working, you will only hear (Feel) sub frequencies. ( 20 - 180Hz ) Another thing that it could be is your receiver setup. Most AV receivers have a menu where you setup the surround sound speaker profile. If you define your front speakers as "large", the low frequencies will not be sent to the sub output. Set them to "small" to enable your sub output.

@@vintageaudioowl1538 Thank you for your assistance and advice. I did check the setup again and it is still set for small front speakers with a 80hz crossover to the sub. I ordered a cable to check the sub and listen for low frequencies. If the sub still works, would you be willing to tackle a newer A/V receiver to diagnose and possibly fix the problem? It is a Denon AVR-2310CI. I believe it is about 10-12 years old.

Hi. I ordered the one I used from mouser. If you go to Audiokarma.com and search "triac power switch modification" or the like in the Kenwood area of the form, you'll find the circuit and part number of the device. As always, proceed at your own risk. :-)

When you get the parts, let me how the installation went and how it's working for you.

@@vintageaudioowl1538 i got the parts but havent installed.... Reason is i had put LED lamps in then the unit to a crap.. Loud humming thru speakers and pop when swiching the selector knob .. So i happen across another working unit, so i blew it out then added LED... NOW that one took a crap and doing the same thing.. Humming and pop when turn ing selector switch... Seems they did not like LED.... as its weird they were both working until i added them... So i took them out and have the correct fuse//lamp coming but in the mean time with all the LED lamps removed it still dead... Im lost to what to check and searching on here

Sorry to hear that. I took a peak at the schematic and I can't see where either the display or meter lamps would cause an issue like you're describing. It's something in common that you're doing between the 2 units but I don't think it's the lamps. Make sure your speaker connections are correct as Kenwoods are picky about that. put the selector to Speaker set A, connect your cables to speaker set A and do not share the speaker grounds. Also, If you set the selector to A+B but don't have both sets connected, neither will work. Also, plug in headphones and see it the problem is there too. Does the noise go up and down with the volume control or is it constant regardless of the volume setting?

@@vintageaudioowl1538 its been a few days but ill recheck.. But i think the noise will go up/down with volume.. Racked my brains out on it,,, Only thing i see that could of happened if it was the LED is the meter lamp Led also lights up on it's tip(top) and lamp may have came forward and touched the metal frame of unit... other than that im baffled...