I just parted with my PM 655 last week. I have been using it since I purchased it new in 1986. Ironically, it had the same issues as the one you worked on. Gave it to a friend to "play with." He called me two days ago and reported that it works fine now. Kind of sickens me but at least I acquired a vintage Optonica integrated amp and tuner. I am going to miss that amp. We had a lot of good years. Hopefully, my friend can get the same pleasure as I did over the decades. Thanks for keeping these awesome relics alive. I wish I had the skills. Respect.

Just found your channel and love it. Thanks for taking the time to teach about what you love.

Harman r very under rated they r a higher end back in the day 35 watt per side u need to run at least a 100 watt speaker they very clean amp if u keep it u will fall in love with it u need a good set of speakers to enjoy it their peaks r strong u will find

@richardgrant5105

4 жыл бұрын

Any chance of using English in your attempt ?

A nice little overview on that amp,I now have a bit more confidence tearing into mine which has random noise in the power amp section.

I had an HK Citation 16 years ago. Easy to work on. It had caps the size of beer cans. I wish I still had it.

I see same problem about bad solder joint on other video about Harman Kardon amplifier and the creator of video (Maxxarcade) complaining about a lot of bad solder joint. That amplifier using Alps blue velvet potentiometer, nice, that potentiometer alone have a value...

Funny story. My pm655 was the first better quality amp I ever had. I used it to do acoustic testing in a club house. On the way home, the catalytic converter in the car overheated. The amp was sitting over the exhaust. The heat boiled the capacitors and melted the thing in general. Put terrible fumes in the car. Drove home with the windows open. Figured out what happened once I got home. Miss that amp. Used to put my speakers in the backyard and play weekend "concerts" with it.

I recently bought an HK 770...You have to admit, Harman Kardon made some beautiful and stout amplifiers

@frankgeeraerts6243

6 жыл бұрын

Just recapped a HK 402a ....................very good sounding nice looking amp.

That was a great video with you explaining everything. Thanks

After watching this video, wish my amp didn't burn up. Wish I still had it. Good to know I made a good choice at the time.

Harman had lots of problems with those push-switches. In my experience about the best you can do is clean the heck out of them, and hope for the best. Since the root of the problem is tarnish on the interior contacts, it helps to exercise them frequently as a preventive measure even if you don't normally use them.

@billnavas4803

6 жыл бұрын

Exactly is the weak point of that series and must be cleaned some times..

Along with checking for DC offset you should also have another meter monitoring the idle current so you don't advance the variac to the point of destroying power stage transistors. The bulb limiter will not always prevent that.

thanx for the video, nice presentation, do more. I have a bunch of these, you need the switch go to ebay and buy a broken unit, get five of them.

It's the 655 model. I have one too and although it runs a little hot it is a great performer. For the missing switch I'd get a lower end parts unit like the 635, they have the same gritty switches. HK had good intentions when they decided to cover the contacts with silver, but as time passes they corrode again and again. A sollution would be to open the switches ad sand down the silver layer.

@frankgeeraerts6243

6 жыл бұрын

I spay them with silver cleaner, wash and protect them with an anticorrosion spray ..

Thanks for your video, it's really great for us. Might you help to give us the recommend for the different between 1 and 2 power supply in PM655 here? Look likes in this model, Harman Kardon they removed the second one of power supplier. And will it impact to quality of mainboard or impact to the quality of signal out to speakers? Again, thanks for your posting here.

I have a 665vxii and one channel just bit the dust. I haven't gotten into it but ordered the output transistors already. I saw one of them smoke.

ITs more likely that the caps fail on higher voltage and pass on lower , then its added leakage , but anyways i didnt get what did you do to make it work , assembled it and it worked . OR was the recap in between

Nice video. I'm curious about the protection circuit. Can you post a zoom in of that portion of the schematic? Or provide a link to the schematic?

I forgot, the 665 VXII just kicks butt.

I have this amp, it was stored for about 18 years pulled it out cleaned it up scratchy buttons etc, inconsistent sound. After cleaning all sounded good. I don't use daily. About 3 months in it started taking longer for the sound to come on after powered up. Deoxitd again every 3 months same and lose left channel, open up deposit on the mechanical speaker pot in the rear and volume switch then all sound comes back again for a few months the same issue any thoughts would be appreciated.

You were talking about doing an upgrade are you still going to do that?? Would be nice!

Would you consider fixing one if it was sent to you?

I still have a HK870,HK825,TU912,HD300 from 87 it was $1419.00, took it out of a 20 year storage & everything works perfect..I couldn't have been more relieved.Everything I've ever seen about this period, solder breakdown is the biggest problem

@xraytonyb

7 жыл бұрын

I agree. I just packed this one up for sale on eBay. Never-ending solder joint problems!

@vinha916

7 жыл бұрын

do you mind share your ebay user ? I will on the look out for your listing. thanks

I know this video is 6 years old, but I can't believe you opted to jump the bass contour control so that it's permanently active. No audio purist would want that, they would want it bypassed. I have two of these, the champagne face PM655 and a black PM655vxi. Got the champagne face one for $15 at Goodwill with the TU915 tuner for $8. All they needed was contact cleaning and they sound amazing.

I have the exact same amp (PM 655), but in black. I purchased it brand new in 1988, IIRC. You have inspired me. I know one of my channels has gotten week because I now always have my balance set markedly off center. QUESTION: What brand of capacitors did you use? I hear there are certain ones which are audio grade (i.e., you mentioned Nichicon). You mentioned the whole set was only about $20 (I guess not including the filter caps?). That sounds awfully low. Can you provide your source? I am looking forward to discovering all the cracked solder joints and putting my amp back to the way it sounded thirty years ago. Thank you. PS: One of my favorite features of this amp is the selectible Moving Coil/ Moving Magnet button. I run both a B&O turntable with a MM and a Dual CS5000 with an Ortofon MC cartridge. However, I have never done much with the capacitance switch - guess I'm not that high a degree of an audiophile.

@frankgeeraerts6243

6 жыл бұрын

I like Epcos ( screw series/low esr long life )for the supply rail..........further Nichicon, ELNA silmic II and cerafine.....i find Panasonic FC witch are good capacitors but to my taste a bit colder and mechanical sounding .... There are many brands and some are very good but impossible to try them all ..........i stick to the one i had good experience with and most satisfaction on listening.

Very nice video as usual . Please feed some music signal to the in put and connect the amp to speaker once the repairing is finished ...... How do you clean that PCB ?.

@xraytonyb

7 жыл бұрын

I usually don't bother playing the amp through speakers on camera because the sound isn't that good through the camera mic. As for cleaning the PC boards, I use a toothbrush and denatured alcohol.

The Harmon Kardon PM665 owners manual shows 100 W per channel at 8 ohms both channels driven 20 -20KHz .08 THD.

@frankgeeraerts6243

6 жыл бұрын

It's a PM655

MOSFET OR TRANSISTOR?

I have a harmon kardon pm645 that keeps blowing main fuse. Any idea where to look inside as to what may be causing it?

@geoepi321975

6 жыл бұрын

check for shorted components

@joeygonzo

3 жыл бұрын

short in the speaker terminal

Have a Hk970 overheating just plays for half an hour and turns off frustrating no bias levels on schematic . Like here didn't see the biasing

I think this is a PM655 not a PM665. PM665 has two transformers, and two pairs of transistores at the power amp.

I’ve been looking for someone to overhaul the amp I have pretty sure it just needs a good cleaning please respond to this comment if your willing to help

Great video! What is the Simple Green cleaner trick? Mix ratios and how to inject it into the pot? How can a hobbyist come up with the schematics and service manuals that y'all wonderful KZread gurus routinely have at hand? Please and thank you.

i would have removed the subsonic filter switch and placed it in the bass contour section

this is a pm655 !!!!!!!

If I find that someone's been there before me the customer gets it straight back unless they've been honest about it up front. Then they get told this may get expensive.

@frankgeeraerts6243

6 жыл бұрын

Got to many tube amplifiers with the request to be re-tubed only but to often they were ( very) problematic because someone messed the circuit up before .....many faulty " upgrades & disastrous modifications " ..............and very often BAD solder work ! Even oil in the tube sockets caused me to wonder what' was going on until i discovered the presence of it ............i changed my attitude on repair , when i was not i informed honestly about the real issues i send them back ....... Not all problems were caused by the owner or a friend of his but some came out of a repair shop who didn't live up to the knowledge of tube technology. Nothing worse than to have an amplifier messed up before you get it for repair ..most of the time without it's original parts and unknown modifications of the circuit , even parts taken out of it .....

1) Are the circuit boards marked +/- for electrolytics? 2) Did you check each cap to see if the markings on it matched where the foil end really is? Apparently there are a lot of mismarked capacitors out there, even new ones: kzread.info/dash/bejne/dKKGwaaFlJS2dKw.html

@frankgeeraerts6243

6 жыл бұрын

Yes , this is a problem , i always mark with a felt pen a point on the board.

You make a mistake my friend that isn't PM 665 .Pm 665 has 2 transformers indipendent and is a mervolous amplifiers with two great black vertical and simmetric sinks...

@billnavas4803

6 жыл бұрын

Is the absolute in quality for the cost of acquisition.The circuit is the best in that period .Looking in the hk 990 you can see a small evolution of citation XX.Better as circuit by worst as power (60x2v hp 990-2x75 v cit XX ,supply power)..

@cukedaddy

6 жыл бұрын

He typo'd it. If you look below the title, he states it's a PM655

you're still looking for a switch just had a look on a site I know it's a 6 pins switch isn't it? I found one it's a latching looks like it will fit in? at 65p each, it's called an ALPS SPPH410100 SWITCH PCB DPST LATCHING AT : cpc.farnell.com/c/electronic-electrical-components/switches-relays-solenoids/prl/results/2?brand=alps Should do the trick had a look at the PDF file the centre pins is common looks like it will go straight in

You never connect on the initial test to loads not knowing if the output stage has DC offset. Yes the protection circuit should keep the relay from engaging however you still can have intermittent (bad connections for instance) that can cause offset after the relay engages that can damage the output stage trying to drive rail voltage into a load before the protection circuit engages. Been there, done that. Solid state amps don't care if there is no load at idle so why take the chance.

What is the downside to this amp sitting for over 10 years not being used?

@frankgeeraerts6243

6 жыл бұрын

Mostly ..........Corrosion on all connections & contacts.............starving/leaking capacitors.........dead solder joints...........dirt build up.....etc.

PATO DONALD 🦆

to jest 655 a nie 665