Harman Kardon 900+ Multichannel Receiver (Ep. 251)

I have one of these. I guess I need to watch and learn as mine is not working.

Boy, that thing looks intimidating...the CD4 board looks like dense, miniature forest of components. 😲

That thing has the most components I’ve ever seen in my life - insane.

Enjoyed thank you

Faultfinding on that monstrosity must be a nightmare. Will never complain again when I have to fix equipment again, not after I have seen what this nigtmare looks inside!!!! Another wild thing is that they use that slide switch to switch the outputs of the amp into bridge mode. Hopefully the contacts in that switch are beefier than what you find in most of those switches. The price of your repair must’ve been insane, and I guess the original price of that thing must make those silly $30000 pre-amps look cheap.

One of these days ill get this treatment done on mine. Wish I still had the wood cabinet

Sucks that the lights on the radio meter are tied to an input, just like Sansui receivers... lame

Another episode of the Get Grey Hair Audio Conditioning Studio ✌️🐻

I have one that's broken

Thanks for the information on this. Gonna save this for whenever i get enough motivation to re-cap my grandfather's. Fortunately it works. So all i really need to do is replace old caps. But that still looks incredibly complex.

Happy New Year Trev. Been around for a few years now. That thing is so old it could have been operated on several times. I had a pristine 730 last month. The lid had never been removed. Always a gamble. I'm finished with gear now. Moving on for 2025. I have saved enough gear for 10 lifetimes. Going back to motorcycles.

Thanks for sharing 2024. Hope to see more projects soon.

What a parts beast!!! Good job! You mentioned it's 50 years old. What about the power supply main caps?

I always thought Quadraphonic stuff was a huge failer for its time. They dont even make Quadraphonic anymore that I know of. And from what I have seen there really is not alot of stuff out there in albums or good albums anyways. I only know of a few 70s stuff that I have found threw stores. And this stuff was not cheap back them for a mid person to even buy this stuff or the albums to as they were not cheap to than a normal album cost. Great work on the receiver tho that was alot of stuff in that one for sure wow. Not a fan of the face of it tho.

Trevor I think the reason those wires are numbered could be Harman Kardon may have assembled a few of their Heath Kits to rebadged it as a Harman Kardon could have been short on parts for the main run of these during line assemblies and just used the kit parts.
Just a guess..

What a strange thing to build. Seems almost a kit thing. Fine work and as always a great video. To me it would seem the value is in the CD4 and matrix decoders and if they could stand alone would be far better to just use just a modern multichannel amp.

Hey Trevor xraytonyb is just starting on a Quad unit if you haven't seen it already. He's really good repairs MRI's for a living so he knows his s***. like you one of the best channels on here.

Wishing you a happy New Year Sir. Trevor is busy these days. You get your moneys worth with Quads (Parts parts parts) Damn, never seen this specimen, I don't think this made it to the States. Along with numbers provided on wires, I like how they are insulated. RCA Power transistors, 1st time seeing. Black widow Transistors (what I call them) Smoke Bombs. All your power outputs were per Mfg. specs.

Thank you, good one! Happy new year to you.. Keep up the good work, very enjoyable!!

Those modification look like something that ham and egger Xray Tony would do "HI EVERYBODY"

We don't often get to see a Quad adventure like this one; time patience, and experience won the day on this unit. I hope you and family had a Merry Christmas and best wishes for the New Year. Thank you for your time!

You're a braver man than me !
I think that must have been really expensive for HK to build and even more expensive to service when it needed any work just because there is so much crammed into the chassis !

That is way too intimidating for me to ever even wanna try. I’m about to try my first recap on an HK 330 C. This 900+ makes my 330 C look like a transistor radio.

Wow! Two quad receiver videos in one morning. Even better, both of them are CD4 equipped. Thanks for this journey.

I have a feeling this client is not going to pay you enough for this repair slash restoration.

Crown Radio Corporation of Japan OEM'ed this receiver for H/K. I noticed the "Crown Japan" logo on the circuit boards. Their Shin-Shirasuna and Roland built receivers are of better quality and I am surprised that H/K used such a lower end, mediocre OEM like Crown Japan to build such an expensive receiver for them. You have more patience than me and If I were repairing that, I would just take my time with it. Whoever designed the layout and ease of serviceability, may it be H/K or Crown did a horrible job and you should charge Quad prices for the labor involved. All of those old Tosin electrolytics just gotta' go.

Happy NewYear; you do fine conscientious work.

You have the patients of a saint. I use to drool over this receiver when I was a kid at the Hi Fi shop. Back in the 70's we were too poor to afford such an expensive awesome thing. I remember the sound of the soft jazz they were playing at the store, nothing we ever had sounded so good. They were amazing receivers in their day.
After what you did to this receiver I'd say it's new resale value is at least $7,675.00. This one should be in a audio history museum. At least now you know how much you should charge for a restoration like this.

So which part do you use/recommend when replacing the SC45s you so dislike? Is there a rationale for deleting these parts?

Trevor (greetings from the West Coast of Canada eh!) I thought you had patience and perseverance on some previous configurations...............but this 'takes the cake'!! I personally cannot see the rationale for the owner to want to have this unit fully restored and the fact that you stated at the outset that with the complexity of this model - your rate $$ would double! There must be some high nostalgic or personal reason to compel the owner to have you spend the time and his/hers $$$ to have this restoration completed. On your part - well done! This established a high-water mark as to your abilities (et al)!! It would be interesting as to the total hours you spent on this restoration and the $$. PS - you viewers who keep stating Trevor's Vids are too long - to you I say 'get lost'! Trevor. Thanks once again for a great year of vids. Health and Happiness to you and your extended family for 2025 (and well beyond) PPS. I wish you were located in 'my back yard' - I have a Marantz 2325 that could really use a 'Trevor Touch' restoration - Ha!

Looks like a service techs nightmare for sure. Kudos to you for even tackling this beast!

Why not start with the power supply? If that is not putting out the correct voltages, then working on anything else first seems unproductive since you're going to have to get the correct voltages out of the power supply eventually. And it might be hard to test amplifier boards unless the power supply is working or you can use bench power supplies. Regardless, the power supply is going to have to be addressed sooner or later... I just can't understand why not sooner.

What was the reason why solid electrolytics on the power amp boards? Not that I disagree. I'm re-capping one of my o-scopes and decided on solid electrolytics where I can get the values.

All Harman Kardon amplifiers imported to Sweden in the 70s had a very poor conversion to the Swedish electrical standards. A lot of overpainted text on the back and removed contacts. Put a sheet metal pop riveted over it. The fuses on the back were removed and glued. The mains switch was not allowed to light red but was replaced by a black one. No fuse on the incoming mains but only fuses on the secondary side of the transformer. In addition, these fuse holders were of poor quality which often caused interruptions. So now when I restore I turn the red button from an old screwdriver handle.

You did a fantastic job! way beyond my skill set. it was a pleasure to watch and thank you for sharing

Gotta love that Joystick also like the fact that the amps are capacitor coupled for that nice flabby bass we all enjoyed back in the day !

I felled sorry after I saw that CD4 board with a part count of a billion. Looked like fields of parts.
Have a great year 🎇

Thanks for all te reat posts this year. Happy New Year!

Thank you for replying and the info!