On Sunday, October 7, 2018 at 4:06:45 PM UTC-4, Steff wrote:
Den 2018-10-07 kl. 03:24, skrev :
On Friday, October 5, 2018 at 8:54:11 AM UTC-7, Steff wrote:
Well just lost a channel at my Harman Kardon 930 Vintage geek as I am I
want to keep my great Reciver and repair it..

What I done sofaar

Check Fuses ( They are OK)
Moving the speakers between the channels left-Right And A and B speaker
outlets.

With this info I understand that the left Channel is ALMOST dead turning
the balance to Left channel I can hear a faint OK sound. (Like the tiny
transistors trying their best before the end power transistors do their job.

My conclution.

1 Not enough power to the end transistors on the left channel.
2 Broken End Trasistors (two 2SC897 according to the scematics)
3 End of preamp broken on left channel.


Most likely End transistors..

Is my thinking OK or did I miss something ?

I am a beginner in HiFi electronics but have basic skills in electricity
as an electrician for 25 years and do know how to solder..

You got some very good advice already. Just want to point out that failed output (end) transistors nearly ALWAYS short out and blow fuses. I've replaced thousands over the years.

I also want to point out that soldering as an electrician is probably different from soldering in a receiver. I recommend getting an old piece of electronics to try replacing a component and see if you can do it reliably. Better to find out on a piece of junk. Older circuit boards have a higher failure rate due to excessive heat. I had an old Sony board where the pads lifted too easily with a 700° tip but were OK with a 600° tip (Metcal).

I like old HK gear and would prefer to hear you have it working again.

G²

I love HK products and specially the older septon ones. So giving life
to my old 930 have high priority for me as well. Mu dad buy it new and
had some JNL speakers with it.. I got is when I left home in 1979 as a
19 year old and it have been with me ever since, so ofcourse I will try
to keep it alive. Best Amp I ever had. I did have a Sansui that was OK
but still this one is the best.

I also have an oscilloscope and multimeter så I will try to separate the
pre amp from the poweramp and se if the prombel is located in the power
amp for sure. I already order some effekt transistors to prepare to
change them since i Still belive it is in the "end transistors"
I found 3 off them in Italy for a decent price (25 USD for 3)

So thanks so far for all advise I keep updating until it works hopefully
with all you guys help.

Sorry for my English My native language is Swedish so bare with me please..



Sad to say, you're English is better than many native speakers...

I've changed many hundreds of outputs over the years, and have never seen one "open". High current/wattage devices *generally* fail catastrophically, not open benignly, although there certainly are exceptions to every rule. So with a basic DMM, check for low ohm shorts. Out of circuit they should read a few hundred K ohms minimum if anything at all. On the diode scale, you should get two combinations that read about 0.600 if the outputs are silicon.

I can't speak for your particular HK, but most amplifiers (not all) use a common speaker protection relay so a shorted transistor on one side will prevent the speaker relay from engaging, rendering both sides mute. Your HK being an older vintage piece may be configured differently.