Harman Kardon A 402 Amplifier - Repairs Part 1 (Ep. 111)

[@Mymohawkisblue]

Beautiful inside ❤

[@TrevorsBench]

A treat for the ears too!

[@joeygonzo]

I'm always on the lookout for this amp.

[@TrevorsBench]

LOL, we all are!

[@SeanBZA]

With coated screws the easiest way to not mar the finish is to use a clear polythene bag, and hold it with the screwdriver, so it makes a thin film between the tip and screw, so there are no marks left.

[@TrevorsBench]

Thanks for the tip.

[@rotaxtwin]

Love your replacement switch caps from your family machinist connection, well done. They look pretty good to me.

[@knifeswitch5973]

That was pretty damn fine work man.

[@TrevorsBench]

Thanks, more to come

[@dennismeehan8189]

Great video. An earlier A402 service video helped me fix a problem I had with mine. It’s a great amp.

[@TrevorsBench]

Yes. the A402 is a real gem

[@SeanBZA]

Not silver plate on those transistors, but tin plate. They are plated with tin during manufacture, so as to keep the copper lead and kovar alloy case (or steel for the cheaper ones, with a kovar slug brazed inside to mount the die) from corroding. Yes likely the driver transistor is open at the base bonding, simplest check is to connect collector to emitter to around 100V via a 1k series resistor, and measure the current as you heat it up to around 200C with a hot air station. 100V should give you enough voltage to see if the collector base junction leakage will cause appreciable current flow, at least over 1uA of current, though at around 150C it probably will start to be higher, and at 200C will probably be a few mA of current flow.

[@TrevorsBench]

Several types of Hitachi transistors are silver plated

[@zdjbel1376]

Great work!! Where did you get the replacement for the broken switch? I need one too. Thanks.

[@frankgeeraerts6243]

Hello Trevor, .............i have a 402 and I want to change those transistors but I do not know the new type numbers to replace those , can you tell what the new replacements are ? Thank you .....I live in Europe .....;

[@GREMLINS516]

Hello you've gave me somme ideas about the ways to check my 402. Mi actual probleme is that i have a difference of volume betwin r/l channels... once of the current default is the switches becoming dry and produce scraches ,so were can i buy them? Apart these problems this amp is fantastic to drive a pair of bw 802 (quite "lazzy") thank's for charingqnd regards from France

[@stefanegger]

with what did you replace the trim pots? Thos version has 2 pins, and most that I saw have 3 pins?!?

[@sh-hq9yk]

What do you use for pots if not the deoxit d5 ? Why is it good for switches but not pots, out of interest ?

[@TrevorsBench]

I use another product CAIG makes called F100. It's formulated for pots and faders. You can get it in spray or drops caig.com/product/deoxit-fader-f100s-l2/

[@joelienhard7867]

I have a 402...left chnl is very low volume and distorting. Would I be able to send u my amp module to be looked at? Would u be able to do and if so what approx would u charge? Unit was working perfect up till a month ago.. ...Thanks much-Joe

[@thedistortedguy]

Hello trevor, i live in a village and no repair technician. I have a doubt can u help me ? I can mail u the problem

[@TrevorsBench]

sure, my email is in the ABOUT page. I might be able to help

[@thedistortedguy]

@@TrevorsBench thank you man. I will mail you the specifics.

[@thedistortedguy]

@@TrevorsBench sorry man, but i couldn’t see a email id in the about section.

[@baocilik5526]

Sorry sirr..... Can you show skema setting bias.....

[@stefanegger]

looks a lot like harman 730 inside

[@mlbabineaux]

Half of the phase splitter wasn't working