This one has me STUMPED! Harman Kardon Eight Twenty Tuner Repair 

I suggest replacing the FET and other transistors. FETs have a nasty habit of testing good when they aren't and if there are several FETs in one section and one is bad, then multiple will act bad. Also make sure there isn't a bad solder joint on the antenna circuit.

The black faced receivers in HK's lineup were known as the 'Nocturne" series with the Eight Twenty (not 820) being king and well worth repairing. I have one here which works well and sounds great but am having some issues relamping it. A 330A I bought new back in '71 has the same FM issue as your Eight Twenty so I'm going to follow this post carefully. Good luck with diagnosing and repairing it. You will be glad you did!

Love these old Harmon Kardon's I have a 330B and a 730. Listen to one or the other every day.

Thoroughly blast the tuning capacitor with high-grade isopropyl alcohol from an aerosol can, let it dry, then put a small drop of F100 (Faderlube) where each of the ground springs contact the moving plates. That can be tricky because of the shield box, but it needs to be done. If it still doesn't work, the best course of action is handing the whole unit over to a tuner expert.

Solid analysis in unknown territory AH. I also have faith in you. It is a sharp looking unit

6:40 Madonna "Boderline". Was the song👌🏼

That 80's song is Madonna - Borderline

I hope one of the suggestions below fixes it I just like your honesty and reaching out for help 👍👍

Working on the little brother to this one the 230a. I changed the electrolytic capacitors and it came back to life. I guess I was lucky seems the HK tuner capacitors are a bit of a challenge.

if you get this issue resolved, please do a updated video.

Solder joint broken in the antenna path somewhere? Your body acts as the antenna when you get close?

That box contains the RF front end of the radio. It probably has an FET RF amplifier and a local oscillator and mixer. One stage of the tuning cap tunes the signal coming from the antenna, and another stage tunes the frequency of the local oscillator, so that when it's mixed with the incoming RF, the output is at 10.7 MHz, which is the std IF frequency for FM radios. Waving your hand over the top must be changing the tuning of something. I would guess the local oscillator. Or maybe it's not oscillating at all when your hand is not there. You really need at least an oscilloscope. Probably the service manual doesn't include the circuitry inside of the front end. Usually that module was simply bought by the mfr from a company that specialized in them. The 820 was a top of the line model from a good company. Definitely worth repairing. Many expensive hifi's back then had tuners that were only for FM. You didn't listen to AM on your stereo system. Most receivers had AM because it didn't add much cost, but the magazine reviews didn't test it other than to say "It worked". The emphasis was on the FM performance.

What you not see or hear very often any more is that a transistor (BJT) needs its .6 V over its base and emitter to work properly. Measure that on these three transistors in that front end of the receiver, so you are sure that the DC bias of these is OK. If they are FET's, thats another story.

That’s an oldie Aiden. Hi Fi Engine says it was made in 1970 with 25 watts per channel into 8 ohms. No need to fix the tuner. Just stand near by with your hand over tuner area and you’ll get great reception! You’re either magic or a good antenna.

because yo have hiss that surgests that the mixer osc is working so i would suspect that the FET may be week at high frequence FM tuner heads can be a pain to work on .

When you struggle to find the problem, and the radio plays "don't stop believing".

Odds are its the RF amp. You can couple a signal in to the gate with just a wire & a low pf cap. If it works you know its between the gate & antenna in. If you dont do the same at the drain. If it works odds are the FET is bad. Also be sure its getting B+ to the tuner assy, somewhere 12-24 VDC. The AGC if way off could turn the RF off but that would be a freak. LFOD !

when you place your hand over you are inducing capacitance to the tuner section, there is your hint..

I guess one of the hardest to fix in a receiver is a failed tuner section.I have no doubt you'll fix that though.

I'm guessing the tuner needs an alignment which I understand is quite involved involving specialized equipment

That thing happens with my antenna, too. If you grab the antenna, you get better music. It even has influence when you go around in the room. So probably your antenna is broken or there is something going one. I hate it when it basically is working and you make 2 steps away and signal goes bad. I don't know why I have this influence on the radio but I have the same influence as you have, just I dont have my radio open that much.

Ask Mr Carlson!

Contour WAS "loudness," HK used to call it "Loudness Contour" as well. Also, they were well-known for FM only, dating back to the Citation III (Considered by many to be a good tuner but one I felt was too unreliable).

Harmon Kardon amps were known for their extra wide frequency response. I was seriously entertaining buying one for my first HiFi on the mid '70's before I went for Luxman. Memories eh?

Did you check antenna continuity? You seem to be completing the circuit for the antenna when you’re near. And if all caps and resistors in the tuner stage check out OK, then a problem with the signal coming in seems a likely culprit.

Prior to 1961 automobiles only came with a.m. FM was still new not many radio stations broadcast FM stereo.

harman/kardon is the BEST. I have 330c, 730 and HK 980 etc.

To be honest sounds like aerial connection from the rear input to the transistor is Brocken hence when you place your hand over it then receives a signal.

Have u tried tracing where u have the antenna connected back to the receiving terminals on the tuning gang? And also have u tried adjusting the 3 trimmers on top of the tuning gang. One of them will b the tuning alignment oscillator,,,the other 2 adjust to receive the station at it,s strongest reception.

You said the first place the signal goes is the IF section. You meant AFTER it goes through the RF section. I don't know, if you can assume, that the tuner cap section from another make and model, is compatible with this HK. That test may be invalid. What you are calling the tuner cap, is the RF--radio Frequency--stage, which contains capacitors, along with other items.

Air-gap tuning capacitors contain rotary (moving) metal disks, that cannot touch the stationary part (chassis) of the air gap tuning cap. Quite possibly, the air gap chassis has become conductively connected to the air gap rotary metal disks. This can be tested using the continuity function of a multimeter. With one probe connected to the chassis of the air gap cap, and the other connected to the rotating discs, there should be no continuity. If the rotating discs are out of shape and therefore touch the chassis, use a flat head screw driver to flatten/shape them so they do not touch the chassis. This could explain why there is no tuning...and why hand capacitance varies the frequency slightly. Alternatively, the tuning dial thread is not causing the air gap cap to move. Check that the thread attached to the dial is actually moving the air gap variable capacitor. A failure of this sort would equally well result in lack of frequency changes and hand capacitance phenomena. Likely one of the above, though might also be transistor/field effect transistor failure, whether or not hFE readings appeared nominal.

I’m thinking this is a tuner calibration issue. The proximity of your hand is changing the capacitance/inductance of the circuit.

I had something similar on an even older device and found a broken adjustable cap. Your hand seems to be acting as to couple in signal as a capacitor. Also check the antenna wires for continuity?

I have read transistors can test fine but still fail in circuit with a load. But your magic hand? That's weird! Time to ask Audiokarma.

Without specialized RF generators and test equipment you're working in the dark. I have had good results by reflowing the solder joints on the tuner can on tuners that had issues. Do not spray anything in the tuning capacitor.

Your shirt is AWESOME!!! Also question... I notice you have the WD40 contact cleaner. how would you compare it to deoxit?

There is a FM muting control on the rear of the unit. Check that circuit.

I just got one for $50 bucks a few months ago. Other than the wood veneer peeling in the front and one of the golden knobs missing, it plays great on my Ovation loud speakers. If anyone is selling the knobs like for the volume, let me know. I'll be happy to buy a few just in case I lose mines.

It's sounds like when your hand is near is closes a ground loop...B&O use the touch of a person to activate most of their equipment using the person as a ground....hopefully it's just a ground loop

Seems the antenna is not getting to the tuning section. Check the antenna connectors on the chassis.

Don’t spray anything in the tuner cap. Blast it only with compressed air. Check the caps in the IF board. Check for a crack in the circuit boards.

I've never seen a model 820. That thing is a real beauty and it has a tone defeat switch. I don't think that even my big boy HK 730 has that feature.

When are you going to update this repair?

Hello, I would like to have your honest opinion about a Marantz 2240, at a price around 430 us $ in good shape and good cosmetics. Thank you.

Madonna's Borderline

love the switches, just like an astronaut....

Dude, I will ship you my Tandberg TR-2060. I think that'd be fun to watch.

The 'cap' is actually a superhet circuit that mixes a 10.7 mhz signal with the station signal to produce a difference output. A scope and the service manual will help tremendously. I suspect your hand is pulling the 10.7 mhz signal back into range.

Madonna - Borderline

I have an Onkyo 2500mkii, power on works if I hold the power button in. If I let go power goes off, it won’t click on. Any thoughts- thanks

A lot of those solder joints look really bad. I would definitely de-solder and re-solder them. Use good solder though. The audio guys like Cardas Quad Eutectic or Kester 60/40.

I only got into the vintage audio repair so not a lot of experience....however maybe it's electro magnetic interference (radio frequency interference) Maybe demagnetizing tool will help? Or better grounding? Best of luck!

Sansui 2000 through 7000 series of this era are outstanding. Did you have a decent antanae attached. Message Xraytonyb or Jordan Pier on youtube. Jordan is awesome at tuner troubleshooting.

It’s sounds like it could be a shielding issue or anttena issue or a tuner issue

Use o-scope to check local oscillator

Great video. Are you in the NY area.

something is open ...ANd this is why you have the antenna effect .usually is a capacitor

Wel if you ask me.. Something is nog right with this receiver!. Hope it helps!😉

Any updates on this?

Does the cover provide shielding? Many older tuners use the cabinet for rf protection.

Hi sir! Did you get this one fixed? Have a great day!

Fly by night sung by RUSH lol

Weird... Wow!

Reach out to "X-ray Tony "

Check the multiplex

could it be the antenna?

These must be rare

So when you wave your hand in front of it you're becoming part of the capacitance. It's enough to get some Claritin the signal. That tuning cap needs some work. Start by cleaning the ground points. Use D5 not wd40. After that it should hopefully improve. An alignment may be needed also. This may be a good one to learn that on. I feel like you already knew this and you're just trolling in your own way with the wd40. Kind of like the power washer. Smh

Madonna- Borderline is the song 🎵 lol

Madonna Borderline

No oscillator so no mixing no output. Easy fix. Find the mixing circuit and troubleshoot that.

maybe 12voltvids or shango 066 would know

holiday, Madonna

I think you are barking up the wrong tree with the tuning capacitor.

Maybe the tuner is overly sensitive to interference from something like the fluorescent, led lights, wifi, or cel signals. When you put your hand over it, it maybe blocking some of that interference. Hopefully somebody more educated with tuners chimes in.

don't ever use wd-40 in any electronic device, please!

Borderline

Sounds like an open RF coil in the tuner cap cage.

GM offered FM in their car radios in 1963. By 1966 most homes could receive FM in new bought radio units. I heard FM for the first time in 1966 in St. Louis, Mo. Smaller towns did not receive FM signals (broadcast for 50 miles back then) for a couple more years. I bought a new 1970 Mustang in Dec. of 69, that came with FM. Seems like ancient history now.

What you refer to as "cap" is actually a whole RF input section. Usually it does tuned amplification and down-mixing using its ow local oscillator to a fixed (usually) 10.7 MHz IF frequency which is then fed to the IF board for further amplification and FM demodulation. This is called a Superheterodyne system. Then follows the MPX stereo multiplex decoder board. Now you seem to have this RF section out of tune. In an oversimplified nutshell you'd need to go stage by stage and tune the resonant circuits to peak amplitude using an RF generatot or a known strong radio station. Of course you must have some equipment being able to measure at these frequencies. Ohh and you must tune it with all shielding lids fully in place. Use a proper non-metallic tuning stick. Also, tuning the RF and IF sections should be outlined in the service manual, I recommend to read and follow that. Good luck! P.s.: you can't just jumper together another RF section to the HK's IF. You must disconnect the RF from the IF in both receivers and use a proper shielded and impedance / amplitude matched connection between the Marantz RF and HK IF. ;)

This brings back unfortunately bad memories as had the exact same problem with a Marantz Mod. 125 FM Tuner, that I just bought and of course paid too much $$$$$ for. Did a service, vellum (LED Lights from your friend in NY) spent a good 4-5 hours on it. No more Marantz for me, I know you love the stuff, Ill stick with Pioneer and Kenwood (1976-1981).

Excellent, I work in Harman Kardon!