Harman Kardon Seven Twenty Receiver - Part 1 (Ep. 184)

In this episode I tackle the dead power amplifiers to see if this 720 will make any noise.
I experiment with replacing the PNP Germanium output transistors with silicon NPN devices

[@SergZak2023]

Good job, Trevor. Thanks for taking the time to share your knowledge. Looking forward to the next installment.

[@TrevorsBench]

Very kind of you, thank you

[@TurntableGuy]

Nothing more fun than sparks and flames!

[@brianwood5220]

Excellent job, Trevor. I would never have thought of changing those PNP transistors for NPN, Experienced sure does go a long way. thanks for sharing. Looking forward to next time.

[@jpkellyburbank]

Thanks!

[@TrevorsBench]

Very generous of you, thanks!

[@chaber6419]

Nice teaser at the end. Looking forward to the Onkyo repairs and your impression. I'd had a few TX1500/2500 receivers come through and I'd love to see a vintage integrated up close. Good stuff Trevor.

[@Reflectiveness]

Great Video.

[@TrevorsBench]

Thanks for stopping by

[@alexismethenitis]

Great work, can't wait for second part!

[@joatmonuk]

Very nice unit.

[@neverwinterasmr6966]

Hey awesome channel. I have a Harmon Kardon 430. It works great but it has one red speaker terminal that is broken off. Any idea where I can get a replacement block or terminals?

[@richhowell5873]

Any chance the unit is for sale? I had one years ago and have been looking to get another.

[@juansabinonava7047]

Hola mister trevors bench. Lo felicito por muy buen video y también pedirle de favor que si tiene el PDF del manual de servicio me lo pudiera pasar . gracias

[@roroseppel2077]

There is a lot of work coming !

[@exenx2995]

Are you still powering up these recievers with the volume turned up like usual?

[@TrevorsBench]

No. those noises were from ancient caps reforming, brute force method

[@stefanegger]

1:05:44 - usually you let it run for 20 minutes, and then set the bias. If you do that, heat wont change much. Also see service manual on the correct procedere. You CANNOT set it up right away as the value will change. That is why.

[@Kirk_Mcgurk]

It's ALIVE!🪄

[@SergZak2023]

FrankenKardon!

[@iceberg789]

i like how they used to stick those power trannies on the cabinet itself and save the heatsink costs.

[@Poppinwheeeeellllllieeeeez]

Some guy use mini ir cameras to see what is getting hot.

[@TrevorsBench]

Truthfully, I did shoot video with my IR camera but it didn't show anything meaningful so I cut that to save time

[@patmeadows4759]

Video is to short!

[@TrevorsBench]

LOL, you guys crack me up

[@johnsenchak1428]

DON'T TURN IT ON AND MAKE SMOKE, YOU GUYS ALL ALREADY SENDING WAY TO MUCH OF THAT FIRE SMOKE DOWN INTO THE STATES LOL

[@Poppinwheeeeellllllieeeeez]

Only send it to your burrow under the bridge John.

[@TurntableGuy]

@@Poppinwheeeeellllllieeeeez LOL

[@johnsenchak1428]

VIDEO IS TO LONG !

[@brianwood5220]

Bollicks

[@robertdavis5714]

So that's why it is so pricey to ship from the States to Canada, thought they invented X-RAY. Entire back plate aluminum and working as the heat sync. Wow, major sparks on this bird. TV repairman leaving the old remains, that 1/2 work annoys the hell out of me. Like your solder spools for elevation change.The worst Sound Wave I have witnessed. Really like that modification with trim pot for every power transistor.

[@TrevorsBench]

Now that I have the output stage sorted I want to go after the rest of the amplifier to see how this sounds