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HK930 service anyone?

oksailor22

oksailor22

New Member
Hello, I'm new to AudioKarma. I have an old 930 twin power that is having some issues.
I'm not very well versed on electronics, but I did go ahead and recap the power supply board. The unit does work, but is is making some ugly noises that are intermittent. A ramdom buzz that gets louder and softer with some crackling. It is an important piece (wife's) and Rather than trying to dig deep into it myself and ending up having someone bail me out anyway, I would like to find a person that can go through it for me and make it as clean sounding as it can be. I'm in Oklahoma and I know no one here that does this type of work. Right now it appears that it is outputting some really high frequencies as well that are bothering my dog. I can't hear it well, but I'm guessing some type of harmonics about 18k or higher. when I turn the unit on. his head snaps around and he heads out of the room. I tested this many times over a month or so and he always reacts this way.... no other systems I have bother him like this. Any help in finding a good resource would be greatly appreciated.
thanks Mark Ayers
 
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Welcome to AK! Can't help you on services in your area just a hearty welcome!
You could inquire with local tv repair shops and ask if they have any audio techs in shop...(older guys usually have experience but don't advertise.)
 
I'd offer to go through it for you, but it might cost you more to ship both ways than it's worth to you. I've worked on a number of these HK x30 receivers, they're some of my absolute faves.
 
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I absolutely love the warmth it has and can understand why these are treasured pieces. I paired this one to a set of Isophon G3037 speakers from the 50's and man it is a wonderful combo, especially so when listening to vinyl.
Where are you located?
 
oksailor22 said:
I absolutely love the warmth it has and can understand why these are treasured pieces. I paired this one to a set of Isophon G3037 speakers from the 50's and man it is a wonderful combo, especially so when listening to vinyl.
Where are you located?
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He said he's in Oklahoma.
 
oksailor22 said:
Sorry, said I was new..... Benricci I meant to be asking you where you were located.. LOL
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Lol, I'm an idiot. Whoopsie! I'm in the Boston area.

Random question - is the noise coming through speakers and headphones, or just speakers? And is it on both speaker outputs (meaning A and B, or just A)?
 
I'm sure you are not an Idiot... the noise is coming out though all speaker outputs and headphones, I thought it was power supply issues and that's why I started with the recap there. Clean in / clean out theory... but alas no change.
pots have all been cleaned and no issues there. All functions work well. I've not separated the preamp from the amp sections to check if it's just on one or the other yet, but I'm probably not capable of fixing either myself anyway....
 
Hmm. OK, well that eliminates some things, which is good and bad. Bad, only because some of those things would have been easy, lol.

Any chance you can snap some pics of the inside and upload them here? Especially where you’ve recapped and the power supplies.

I have the service manual around here somewhere for the 930, let me go find it.
 
oksailor22 said:
Kind of Proud about doing the recap... I was very nervous when I first flipped on,,, but hey it worked :)
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sorry, probably not the best pics...
I'm heading home from work now but will check back in later to see if you have any things for me to try. I do have the service manual downloaded as well. thanks Mark
 
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IMO if you did the caps you can replace other components. Perhaps @benricci can pitch in for what to look for. Noises through the audio path (static) hints on transistors. Understand that amps do just that, amplify anything in the audio path. There may be known trouble maker transisors See @dlucy sticky top of page, perhaps others will chime in and examine the sm / same.
---You can also look for cold or aged solder joints, many common issues have been resolved. ground wires, transistors etc. transistors do get hot and cold and the solder can age. check your work done already, too. Strong magnifying glass.
--- This amp has pre-in main-out jacks that if you have another amp you can check these amp stages for the noise.

Sm (I know you have it already)
https://www.hifiengine.com/manual_library/harman-kardon/930.shtml
 
Binkman said:
IMO if you did the caps you can replace other components. Perhaps @benricci can pitch in for what to look for. Noises through the audio path (static) hints on transistors. Understand that amps do just that, amplify anything in the audio path. There may be known trouble maker transisors See @dlucy sticky top of page, perhaps others will chime in and examine the sm / same.
---You can also look for cold or aged solder joints, many common issues have been resolved. ground wires, transistors etc. transistors do get hot and cold and the solder can age. check your work done already, too. Strong magnifying glass.
--- This amp has pre-in main-out jacks that if you have another amp you can check these amp stages for the noise.

Sm (I know you have it already)
https://www.hifiengine.com/manual_library/harman-kardon/930.shtml
Click to expand...

Thanks for the vote of confidence, but what I really want is someone who has the equipment (ie) an oscilloscope and better soldering skills than I have to go through it properly. It took me months of prep and worry just to do the big caps and I was very nervous about those... Since this unit is my wife's (for 20+ years) I need to make sure it's done right. I would like to learn how to fix and upgrade things like this, but I just cannot do that right now. my other (good) system consists of a Yamaha natural sound pre-amp, McIntosh MC7100 driving some Snell EIII and split off through a Lucas Film crossover to a Polk Subwoofer. so I'm used to some pretty good audio, but this system does not have the warmth of the Harmon Kardon, so my eventual thought is to use the HK930 as my pre-amp for the McIntosh. but it has to be repaired correctly first.
I will see about checking the pre-amp side separated from the amp section on the HK930 today and will let you know the results.
 
bumping my own thread here, but I'm about to ship this thing across the country to someone I don't know to see if they will go through it. Does anyone have any better ideas... Apparently audio repair is dead in Oklahoma.
 
I have this very same receiver fully recapped. It's really an awesome sounding receiver! One of the best I've heard.

I'd suggest you to send it over for someone experienced in audio restoration work to service it over, since you don't have any prior experience on restoration work. This is not suitable for a first restoration project for anyone for the sake of the tone board. Also the lowest row caps on power amp are little tricky, but nothing like the tone board. To remove tone board to 'service position' you need to desolder several wires from the board, since the wires don't have much slack to move the board around. I marked and removed several wires out of my way and that only allowed me to lift the board say 45 degree angle or little more, so one needs to be careful while working there.

All the original electrolytics on the tone board and on other boards were heavily drifted out of spec, but no wonder it's nearly 50 years old receiver. So there you might have a source for your strange high pitched noise from the receiver power on.
 
a fellow audiokarma person recommended Manymoons audio in Tulsa, I've got a message out to him already! I do just love the richness of the sound of this amp. I've got it hooked to a pair of Isophon G3037 speakers and it is a great combo!.
I'm using my Mcintosh and Snell EIII's for comparison so you know what I mean when I say "great combo"
 
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