Harman Kardon 630. I did a thing.

[sunvalleylaw]

New home.

 

[sunvalleylaw]

 

[sunvalleylaw]

When it's time to look at the electronics, open it up, check for signs of stress, ie, discoloured resistors... Check fuses
are ok and correct rating (found a 20A fuse where a 2A should have been). Build a Dim Bulb Tester, a current limiting device,
numerous plans on AK and power up on DBT. A variac would be nice... Then basic health check of power supply voltages
and bias, dc offset...

Pulling this post of mine from @hopjohn 's blazing a trail 630 restore thread for my own journey and figuring stuff out. Will start with the above after I pull it out and remind myself what was going on when I put it away.

Marking this to come back to as I pulled my 630 several months ago as it was acting up and I did not have time to figure it out (I am not super skilled, kinda beginner on restoring these things). I am going to pull it back out and recall what was going on, and start figuring it out from there. AFAIK, this unit had not been restored or updated at all.
View attachment 3826639

 

[sunvalleylaw]

Sometimes fix and repairs are easy, others can be a grind. Good luck with it. My fix and repair 330C sold as "no output" just needed its controls cleaned and a few new bulbs (tuning meter, power button, and stereo light). Someone put LED fuse lamps for the tuning dial not sure why they did not do the one for the tuning meter.

I have had lots of units like that since I started this thread. Many of them HK early 80's units with the champagne colored fronts as my family had when I was a kid. Those seemed frequently to need the pots and switches cleaned up. And then they need it again a while down the road it seems. I still have not put any re-cap or electronic upgrade work into any of those, as for a while, they were so cheap, I kept running across "spares" to adopt and bring home to see if I could clean them up and get them to work. Almost always, it has worked. I had one die on my to some issue with the power supply that maybe can be fixed. Anyhow. that was that series. Now back to this Twin!

 

[sunvalleylaw]

Well, if I had not been in such a hurry before, I may have found that I had simply blown the left speaker fuse. Everything else seems to be currently in working order, and the pots all turn cleanly and nicely. I may hit them with d-oxit and faderlube again since it is open.

THAT SAID, I am concerned about the upward somewhat subtle bulging of those black capacitors and they are making me nervous. As said, I am inexperienced with replacing capacitors and going to learn better soldering (I can do some) at a class at the Reusem Computer and Electronics recycler in Boise. But meanwhile, not really comfortable using this for fear of bursting a cap and messing things up. Unless some of you all think I am being over cautions. Will review other threads to figure out what I want to use, and what other re-capping or restoration I want to do. While I am NOT a purist, I hope to preserve the intended sound and function.

 

[kirbjas]

My 2 cents.. I would be very suspicious of any physically bulging or leaking caps and would replace them for sure. Not hard or super expensive but good idea to learn and practice soldering on other things that you don't care about too much first. The best hk 630 thread I have come across is this one https://audiokarma.org/forums/threads/harman-kardon-630-twin-powered-blazing-a-trail.911113/, which I see you already found. I used that as a reference to do a full restore on a 630 which turned out really nicely. There are different opinions on doing full restores vs not and the hk 630 is not an ideal receiver to work on for a first restore since it's challenging to access some boards and the traces are fragile. I would think if your filter caps are shot then likely you would want to do at least a recap of all electrolytic caps in the power supply and test to make sure you have correct and stable voltages going to all boards. Also at a minimum, I would check the dc offset which I think is a common problem on hk 630s and 930s.

 

[sunvalleylaw]

My 2 cents.. I would be very suspicious of any physically bulging or leaking caps and would replace them for sure. Not hard or super expensive but good idea to learn and practice soldering on other things that you don't care about too much first. The best hk 630 thread I have come across is this one https://audiokarma.org/forums/threads/harman-kardon-630-twin-powered-blazing-a-trail.911113/, which I see you already found. I used that as a reference to do a full restore on a 630 which turned out really nicely. There are different opinions on doing full restores vs not and the hk 630 is not an ideal receiver to work on for a first restore since it's challenging to access some boards and the traces are fragile. I would think if your filter caps are shot then likely you would want to do at least a recap of all electrolytic caps in the power supply and test to make sure you have correct and stable voltages going to all boards. Also at a minimum, I would check the dc offset which I think is a common problem on hk 630s and 930s.

Thanks very much for those tips!

 

[kirbjas]

I should also mention checking and adjusting bias as another minimum must do item, after you make any changes to caps or other components in the power supply or main amp. These receivers are definitely worth repairing and restoring, and look and sound really nice.

 

[sunvalleylaw]

I should also mention checking and adjusting bias as another minimum must do item, after you make any changes to caps or other components in the power supply or main amp. These receivers are definitely worth repairing and restoring, and look and sound really nice.

Another thing to learn how to do properly. Then, I want to learn to do repairs on my Hafler amps and pre-amp, including bias and dc offset on those amps. They ended up out of service due to issues and I was pretty sure bias and dc offset has something to do with it from reading here I did at the time I pulled them.