Harman Kardon 430 - Left Channel Noise
- Thread starter JB8
- Start date
JB8
Well-Known Member
After spending a couple more hours trying to track this issue down I'm officially stumped, could not identify any specific failed components or concerning voltages.
@ecluser, you had an epic thread some 10 years ago where you helped someone track down a hiss/hum in a 430. I've read that thread several times, super helpful, but I'm still struggling to identify the issue.
To nutshell where we're at:
- HK 430 with hiss at start up, does not change over time, present at no volume across all functions (heavier in left channel but it's on the right channel as well) The hiss sounds like white noise, heaviest in the 400 Hz range
- After replacing the 1345's and 458's on the maim amp board (both channels, used 1845's) there was no change
- Since the hiss is significantly louder on the left channel I also replaced the 2SA777's and 2SC1509's with KSA1220's and KSC2690's. (Early in the process it was suggested that I swap the two channel components until I found the culprits but I decided to replace them one by one instead) still no change. * I haven't replaced the 777's and 1509's on the right channel yet since their siblings on the left channel were not crazy out of spec when tested out of chassis, could this create an imbalance across the channels?
- I had already wanted to recap the unit, so I recapped the main amp board along with the caps on both rectifiers and the main filter caps, all with original values. Slight change, hiss is slightly louder now. *I've double checked all of my pinouts for everything I've replaced, all are correct based on original orientation and schematic)
- I attempted to use an oscilloscope I picked up recently but I'm not convinced it's accurate, that said, I am getting a less steady sine wave on the OUT from the main amp on both channels than what I get from the IN test post (pics on page one of this thread)
- I've checked some of the voltages you noted in your thread from 2011, zener seems fine, 26.9 DC volts 0 AC volts at LP54 and 24.75 DC volts and .01 AC volts at LP501 (not sure if this helps but added as reference just in case)
- Idle has been adjusted to ~24 mV
- When I turn up the volume just past the lovely "sound of the ocean" hiss the unit sounds fantastic
- And yes, I've bathed the pots in Deoxit, so I'm assuming they're clean and shouldn't be the issue
The two other gentlemen on this thread have been super helpful, thank you, but I'm still a bit lost and I'd prefer not replace any other components until I have a better idea of some specific things to check. I love this unit but I'm convince that if I randomly probe around I likely won't come across the issue. I'm still a noob at this depth, really appreciate the help from everyone.
Can't live with this hiss and I've had several other 330c's and 430's that were very quiet at zero volume, thanks in advance for any guidance you can provide.
JB
@ecluser, you had an epic thread some 10 years ago where you helped someone track down a hiss/hum in a 430. I've read that thread several times, super helpful, but I'm still struggling to identify the issue.
To nutshell where we're at:
- HK 430 with hiss at start up, does not change over time, present at no volume across all functions (heavier in left channel but it's on the right channel as well) The hiss sounds like white noise, heaviest in the 400 Hz range
- After replacing the 1345's and 458's on the maim amp board (both channels, used 1845's) there was no change
- Since the hiss is significantly louder on the left channel I also replaced the 2SA777's and 2SC1509's with KSA1220's and KSC2690's. (Early in the process it was suggested that I swap the two channel components until I found the culprits but I decided to replace them one by one instead) still no change. * I haven't replaced the 777's and 1509's on the right channel yet since their siblings on the left channel were not crazy out of spec when tested out of chassis, could this create an imbalance across the channels?
- I had already wanted to recap the unit, so I recapped the main amp board along with the caps on both rectifiers and the main filter caps, all with original values. Slight change, hiss is slightly louder now. *I've double checked all of my pinouts for everything I've replaced, all are correct based on original orientation and schematic)
- I attempted to use an oscilloscope I picked up recently but I'm not convinced it's accurate, that said, I am getting a less steady sine wave on the OUT from the main amp on both channels than what I get from the IN test post (pics on page one of this thread)
- I've checked some of the voltages you noted in your thread from 2011, zener seems fine, 26.9 DC volts 0 AC volts at LP54 and 24.75 DC volts and .01 AC volts at LP501 (not sure if this helps but added as reference just in case)
- Idle has been adjusted to ~24 mV
- When I turn up the volume just past the lovely "sound of the ocean" hiss the unit sounds fantastic
- And yes, I've bathed the pots in Deoxit, so I'm assuming they're clean and shouldn't be the issue
The two other gentlemen on this thread have been super helpful, thank you, but I'm still a bit lost and I'd prefer not replace any other components until I have a better idea of some specific things to check. I love this unit but I'm convince that if I randomly probe around I likely won't come across the issue. I'm still a noob at this depth, really appreciate the help from everyone.
Can't live with this hiss and I've had several other 330c's and 430's that were very quiet at zero volume, thanks in advance for any guidance you can provide.
JB
nicholas2381
Super Member
Sorry you didn't find the source of the problem yet. Stick with it. Apologies but I seemed to misunderstand last night. I thought the double sine wave was isolated to the trouble channel, but it seems it's present on both?
I'm going to ask some basic questions (not to be insulting, just to get a sense of everything) to see if I can be of more assistance. You may have already been through these various steps, but can't hurt to double check. Others may certainly have more/better advice.
Does the hiss change if you touch the chassis or any of the knobs? How about the RCA of the input?
Does the hiss change if you adjust any of the tone controls?
Is the hiss present on all inputs?
Is it amplified on the phono input?
Is the hiss present on both speaker 1 & 2 outputs?
If you swap your RCA cable so L becomes R and R becomes L does the hiss follow suit?
Have you checked your ground connections?
Have you checked for cracked solder joints?
Have you checked for tiny solder bridges?
My HK 630 also has a slight hiss at the speakers but you have to have your ear up next to a speaker to hear it.
I'm going to ask some basic questions (not to be insulting, just to get a sense of everything) to see if I can be of more assistance. You may have already been through these various steps, but can't hurt to double check. Others may certainly have more/better advice.
Does the hiss change if you touch the chassis or any of the knobs? How about the RCA of the input?
Does the hiss change if you adjust any of the tone controls?
Is the hiss present on all inputs?
Is it amplified on the phono input?
Is the hiss present on both speaker 1 & 2 outputs?
If you swap your RCA cable so L becomes R and R becomes L does the hiss follow suit?
Have you checked your ground connections?
Have you checked for cracked solder joints?
Have you checked for tiny solder bridges?
My HK 630 also has a slight hiss at the speakers but you have to have your ear up next to a speaker to hear it.
JB8
Well-Known Member
No worries at all! Sometimes it's tough to gage how far and deep people want to go specific to walking through all the troubleshooting steps, so I try to be mindful of people's time and not pummel them with questions. After I replaced the other two main filter caps last night it became more obvious that this was across both channels, just louder on the left. And yes, the double sine is happening across both channels, should have made that clearer. Like I mentioned, I've had several 430's and around 20 330c's and none of them had this level of noise. I have my first 330B arriving next week, stoked to check it out as well!
Ok, on to the questions, and don't worry, not insulted at all.
Ok, on to the questions, and don't worry, not insulted at all.
- Does the hiss change if you touch the chassis or any of the knobs? How about the RCA of the input? If I lightly tap the bare chassis with the pad of my finger I can here a tiny little pop sound, but mainly on the right speaker and/or through the headphones, but it's not a hard, fully panned right so I imagine it's showing up some on the left channel as well, same happens with touching/tapping the RCA's. And no change if I reverse the polarity of the two prong plug, no change at all
- Does the hiss change if you adjust any of the tone controls? Yes, both Bass and Treble are impacted if adjusted + or -
- Is the hiss present on all inputs? Yes
- Is it amplified on the phono input? No
- Is the hiss present on both speaker 1 & 2 outputs? Yes
- If you swap your RCA cable so L becomes R and R becomes L does the hiss follow suit? I don't have any RCA's hooked up to it presently, but if I swap the speaker leads (L/R) it follows
- Have you checked your ground connections? No, which connections should I be addressing specifically?
- Have you checked for cracked solder joints? Yes, I've gone over primarily the main amp but also much of everything on the underside of the unit, did not see anything of note that needed attention
- Have you checked for tiny solder bridges? Yes, but I can certainly check again. Did not appear anyone else had been mucking around so I made sure all of my new solders were proper
nicholas2381
Super Member
I'm not an expert by an means, just a fan of the hobby. I've received a ton of support from folks on this board so I try to pay it forward when I can. I'm also a fan of the HK twin power series so love to see them getting fixed and enjoyed.
Let's set the scope findings aside for right now. I may have led you astray there and it sounds like you don't have confidence in the scope.
Since the hiss responds to adjustments of the tone controls, it's probably smart to check the Tone Preamp Board.I'd verify these voltages to start:
Let's set the scope findings aside for right now. I may have led you astray there and it sounds like you don't have confidence in the scope.
Since the hiss responds to adjustments of the tone controls, it's probably smart to check the Tone Preamp Board.I'd verify these voltages to start:
nicholas2381
Super Member
Some of the voltages on 503-506 seem high. Was the volume set at minimum? Balance and tone set dead center?
nicholas2381
Super Member
OK, then I would check the caps and resistors on those boards. Seems like something might be off following the volume pot in the signal path.
JB8
Well-Known Member
Swapped out all caps on the tone board.
C503,504 drifted from 10 uF to ~14 uF
C505, 506 drifted from 22 uF to ~30-33 uF
C513, 514 drifted from 2.2 uF to ~3 uF
C517, 518 drifted from 47 uF to ~60 uF
I upped the voltage on most of them except for C513 and 514, no change, the hiss is wonderfully strong, still louder on left channel, but I'm slowly replacing all the caps on the board, sweet!
For the resistor testing one typically needs to pull one leg, test with power off, etc. There are well over 30 resistors on this board, do I just need to start at one end, testing each one? And how far off from factory specs do they need to be before they need to be replaced?
Feel like in the end it's going to be something super simple, hopefully, and I'm fine with that, staying patient, ha!
C503,504 drifted from 10 uF to ~14 uF
C505, 506 drifted from 22 uF to ~30-33 uF
C513, 514 drifted from 2.2 uF to ~3 uF
C517, 518 drifted from 47 uF to ~60 uF
I upped the voltage on most of them except for C513 and 514, no change, the hiss is wonderfully strong, still louder on left channel, but I'm slowly replacing all the caps on the board, sweet!
For the resistor testing one typically needs to pull one leg, test with power off, etc. There are well over 30 resistors on this board, do I just need to start at one end, testing each one? And how far off from factory specs do they need to be before they need to be replaced?
Feel like in the end it's going to be something super simple, hopefully, and I'm fine with that, staying patient, ha!
nicholas2381
Super Member
Keep at it! She’ll be ship shape once you’re done.
for now, since the his is louder in one channel, I’d stick to the resistors in that signal path.
I don’t have the manual or schematic in front of me at the moment, but I suspect most of the resistors are 1/2 w or 1/4 w carbon composition so likely 20% tolerance.
for now, since the his is louder in one channel, I’d stick to the resistors in that signal path.
I don’t have the manual or schematic in front of me at the moment, but I suspect most of the resistors are 1/2 w or 1/4 w carbon composition so likely 20% tolerance.
nicholas2381
Super Member
For now, stick with the tone board. You could check the voltages on the transistors again to see if the cap changes brought them in line with those listed in the manual. If so, then the resistor values may be OK.
JB8
Well-Known Member
I got sidetracked, started thinking more about the main amp and the voltages that would be quick to check.
All of the main amp B's (+-B1, +-B2) were just over 30 volts, 30.24-30.35 volt range. Is this of concern since they're all supposed to be +-28.5 volts? Since we're tracking higher values on the tone board could it be that the main amp is feeding too much power and the noise is amplified because of that overage?
For reference, +B4 was 24.81 volts and +B3 was 12.35 volts, both seem fine.
Totally fine checking the tone board resistors but wanted to make you aware of these values just in case they're helpful.
All of the main amp B's (+-B1, +-B2) were just over 30 volts, 30.24-30.35 volt range. Is this of concern since they're all supposed to be +-28.5 volts? Since we're tracking higher values on the tone board could it be that the main amp is feeding too much power and the noise is amplified because of that overage?
For reference, +B4 was 24.81 volts and +B3 was 12.35 volts, both seem fine.
Totally fine checking the tone board resistors but wanted to make you aware of these values just in case they're helpful.
nicholas2381
Super Member
I’m not really sure. I’d suggest calling in the experts to get that answered definitively. Maybe. @dlucy or another more experienced member can assist. I’ve got unbelievable amounts of help from @merlynski in the past.
I don’t want to send you on a wild goose chase.
I don’t want to send you on a wild goose chase.
JB8
Well-Known Member
Thanks, Nicholas, I appreciate your candor. If someone else chimes in, great, but if not I may need to shelve this guy for a bit then revisit it when I can really dissect it slowly and pull each resistor to check for values. It's a tedious process but one I'm prepared to do if the consensus it that it's likely a tone board issue and not tied to the main amp or a grounding issue.
In the meantime I'm going to swap out the rest of the transistors on the right channel so the main amp is better balanced. I'd replaced the 777's and 1509's on the left channel (even though they weren't the issue) so I'll get the right done too, may as well. Thanks again!
In the meantime I'm going to swap out the rest of the transistors on the right channel so the main amp is better balanced. I'd replaced the 777's and 1509's on the left channel (even though they weren't the issue) so I'll get the right done too, may as well. Thanks again!
nicholas2381
Super Member
JB8
Well-Known Member
Fantastic! Thanks to you both, much appreciated. 
@merlynski, all main amp transistors have been replaced along with all main amp caps, also both rectifier boards. Main filter caps replaced as well as the tone board caps. Tone board is the only place I upped the voltages, the rest of the boards have factory values.
Hiss on both channels, much louder on the left, not effected by volume. All removed/replaced parts tested ok but all had drifted due to time. Hiss is across all functions, unit seems to perform great otherwise once we're past the level of hiss.
Specific to Q402 and Q404, they were replaced with 1845's but unfortunately I didn't spend time to get them "matched", still learning, need to do a better job with matching...
That's where we're at, what do you think?
@merlynski, all main amp transistors have been replaced along with all main amp caps, also both rectifier boards. Main filter caps replaced as well as the tone board caps. Tone board is the only place I upped the voltages, the rest of the boards have factory values.
Hiss on both channels, much louder on the left, not effected by volume. All removed/replaced parts tested ok but all had drifted due to time. Hiss is across all functions, unit seems to perform great otherwise once we're past the level of hiss.
Specific to Q402 and Q404, they were replaced with 1845's but unfortunately I didn't spend time to get them "matched", still learning, need to do a better job with matching...
That's where we're at, what do you think?