Harman Kardon 730 Receiver Repair (Ep. 160) 

I've had a 730 for about a decade, all I have ever done is give it a good cleaning and replaced some bulbs and it just preforms. It was my first "Dual Power" unit, since I've added a Luxman and Sansui. It is hard to believe how clean and simple the engine bay is, I remember working under the hood of a 72 Chevy pick up with my dad and the 730 reminds me of that truck...

"Transistor-itis", That put a smile on my face! 😂

I feel same way about my old pioneer and my old Peavy bass amp.

I have a Montgomery Wards model 450, it was built by HK custom for wards and it has the same power board as the Hk730. Would it be ok to use the KSC-1845 to replace all the 2SC14 transistors? I'm lost at why you have to build a circuit to match resistors. I'm not a service tech or engineer so I'm relying on videos like yours for help. Any advice would be greatly appreciated.

Most excellent, the older simply designed audio gear do sound nice.

Thank you for the nice video Trevor ..........I have a 730 and have bad output transistor on one channel , ..........if you please can you tell me the replacement types ..?

Nice one!😊

My bench runs an HK330 blackface. Love that little receiver.

Hi TB. I’m just starting the video and you have lost your reference noise. My suggestion would be to inject some heat or cold to the suspect components. Well back to watching the rest of the video😀

Nice old HK

Trevor, can you go over how you got the inside of the unit looking almost new. Is the only way to get it that clean is to completely disaasemble the unit. Even then how do you get the boards so clean? Than you.

Thanks for the problem finding mission! But you have to find a way to keep the osciloscope camera focused!

Thermal cool it off

Why you don't use the transistor tester to find matched pair transistors (by matched hfe)?

I enjoyed your video...great job!

Are you sure the method to match transistors at 18:00 is correct? You plug any transistor, will show the same collector voltage. Regards.

Thanks for very nice movie. HK730 is interesting amplituner indeed. You mentioned DC offset. Fortunately it was ok for your HK730 but how to deal with DC offset in the receiver, which has no controls (e.g. VR) for that. It is the case of HK730, there are VR to set up bias current but nothing to set up DC offset.

What is the function of Q405/406?

Hello. I think the reason could be in the connectors of the power transistors.

Dude, don't you need matched pairs in the differential amp that closely match the original specs