This is the kind of video i was looking for . Full troubleshooting. Thank you . Amazing how much i got from that . It makes me look differently at my past restorations.
Hello. It may not be responsible for the difference in channel gain you are experiencing, but the PCB looks stained/burnt at the area you are zooming into. Could 1 or more components at that point have been fried?
Hi Jordan, I have the same amp and I recapped it myself (sounds much cleaner now) but even before the recap this amp had a faint audible hiss or noise (feedback)? that is mostly audible on the mids and tweeters (not sub) on any source Aux phono tape etc that can be heard when you pause the music (hard to notice while music plays) and it varies with the volume, below 25% is quite as it should be and from 30-40% it makes that hiss and at 50% of vol is quite again, I get the same hiss or buzz noise if I use the amp as a pre amp with an external amp so I guess the problem is in the pre-amp section... I kinda suspect the vol control, I cleaned it many times but makes no difference any thoughts?? THANKS and great job on your amp.
Hi, @elliott-mtb5599 , got the same symptoms with mine 7055A. I would try the method proposed here to attenuate the preamp with resistors between selector and input. My have some traces being flooded, so the preamp components have drifted away (my understanding). So input gain is very high and it is picking interferences at around 9 o'clock.
Cool. The case and face are in great shape. I have used dawn dishsoap in the ultrasonic on knobs. Lemon lysol wipes wrung out of excess cleaner on the face plate and mothers aluminum polish to great success. Baby wipes are good at cleaning grime. Are you going to polish the rca jacks? Loving this series.
Never worked on any. They don't come up around these parts. I have a few but they all still work. Something I may consider getting into. I get asked this question alot.
I'm surprised that you didn't replace the other double diode bead with two 1n4148's as well. Just to make sure the other channel won't play up later. 82k loading, i would have cheated and stuck a 200k preset to tweak to perfection :-D Odd how there is a difference in level.
Is that slight channel difference really important? Would you even hear it? Seems like a lot of labor an owner would pay for a middle of the line receiver.
@@JordanPier nice video. Mine have a buzz, dependent on preamp input impedance. Did not experiment with adding resistance. Where exactly is the best place: after selector sw and before monitor switches and stereo/mono or after stereo sw and before balance?
I wish. Tried pulling the display and cleaning the contacts, to no avail. It appears to be a problem on the 79iii displays. Fluke no longer supports it
@@JordanPier It looks like one of the backplane lines are open. If you take the display out, try to touch one of your power supply leads to one of the outside tracks on the LCD, and swipe your finger across the others. You should be able to light every segment up. It probably has no more than 3 backplane lines, 2 on one end, one on the opposite. If you can see all the segments, than probably the zebra strip is the cause. You might also turn on the meter, and scope the pcb gold terminals one by one to make sure there is signal there.
True. Alot quicker. I can usually tell where to start based on the volume control value. 150k didn't do enough, 100 was close, 82k was about as close as I could get it
Hey Jordan enjoy your content sounds like you’re in Southern California somewhere have u ever mentioned what or where the shop is I’m having trouble finding a reliable tech in so cal I have a 70s kenwood receiver I’d like to have work done on u really look to be on the ball
This is the kind of video i was looking for . Full troubleshooting. Thank you . Amazing how much i got from that . It makes me look differently at my past restorations.
Its a Joy to watch you work. Much appreciate the videos.
This is some kind of adventure in troubleshooting and problem solving. Waiting for Part 4! Thanks for your time.
Hi JP. Great to see you found all the problems . Looking forward to your next video. All my best.
the time spent on this would probably buy 3 new ones but the fun factor is excellent - I really enjoy this
beautiful amp. thanks. looking forward to part four
Cool video, thank you.
Hello. It may not be responsible for the difference in channel gain you are experiencing, but the PCB looks stained/burnt at the area you are zooming into. Could 1 or more components at that point have been fried?
Hi Jordan,
I have the same amp and I recapped it myself (sounds much cleaner now)
but even before the recap this amp had a faint audible hiss or noise (feedback)? that is mostly audible on the mids and tweeters (not sub) on any source Aux phono tape etc that can be heard when you pause the music (hard to notice while music plays) and it varies with the volume, below 25% is quite as it should be and from 30-40% it makes that hiss and at 50% of vol is quite again, I get the same hiss or buzz noise if I use the amp as a pre amp with an external amp so I guess the problem is in the pre-amp section... I kinda suspect the vol control, I cleaned it many times but makes no difference any thoughts??
THANKS and great job on your amp.
Hi, @elliott-mtb5599 , got the same symptoms with mine 7055A. I would try the method proposed here to attenuate the preamp with resistors between selector and input. My have some traces being flooded, so the preamp components have drifted away (my understanding). So input gain is very high and it is picking interferences at around 9 o'clock.
Cool. The case and face are in great shape. I have used dawn dishsoap in the ultrasonic on knobs. Lemon lysol wipes wrung out of excess cleaner on the face plate and mothers aluminum polish to great success. Baby wipes are good at cleaning grime. Are you going to polish the rca jacks? Loving this series.
Isn't it possible that freezing the diode could also be fixing a dodgy solder joint?
Hi Jordan, could you go into detail abit more where you put that resistor to balance out the channel ?
Basically shunting the input to the preamp from the output of the selector switch
Wow, Sony did cable lacing back then. Or did you do that to clear the work area?
Yes, cable lacing was a thing even then. I tidied it up a bit.
Hey Jordan, why don’t you do VCR repair videos?
Never worked on any. They don't come up around these parts. I have a few but they all still work.
Something I may consider getting into. I get asked this question alot.
Jordan the blue capacitor I think it is c217, it looks weird.
Could it be your scope inputs are slightly off, did you try swapping leads ?
I did. I used the calibration test points on the scope to validate the proves and scope were accurate
Yepp, Connecting both leads to the same point and verifying that they then show the same signal might be a good idea.
Also could use Channel 1 Plus Channel 2 input mode. Invert one channel for difference.
Question. What is the correct bolt size for the rubber feet of a Sony STR-6055?
Thanks.
No idea. If you have an existing screw get it matched at a hardware store. If not it's a trial and error of ISO screws and thread types.
At 11:26 that light blue capacitor looks bulge.
I'm surprised that you didn't replace the other double diode bead with two 1n4148's as well.
Just to make sure the other channel won't play up later.
82k loading, i would have cheated and stuck a 200k preset to tweak to perfection :-D
Odd how there is a difference in level.
I still might replace the other diode as a precaution. Gonna burn it in some more and see.
Is that slight channel difference really important? Would you even hear it? Seems like a lot of labor an owner would pay for a middle of the line receiver.
It is noticeable. Maybe moreso in a controlled environment with good acoustic treatment. 7065 was the top of the line for Sony that year
@@JordanPier nice video. Mine have a buzz, dependent on preamp input impedance. Did not experiment with adding resistance. Where exactly is the best place: after selector sw and before monitor switches and stereo/mono or after stereo sw and before balance?
Hi, jordan
Your Fluke multimeter's display might need cleaning. I do know that you are a excellent tech.
I wish. Tried pulling the display and cleaning the contacts, to no avail. It appears to be a problem on the 79iii displays. Fluke no longer supports it
@@JordanPier It looks like one of the backplane lines are open.
If you take the display out, try to touch one of your power supply leads to one of the outside tracks on the LCD, and swipe your finger across the others.
You should be able to light every segment up.
It probably has no more than 3 backplane lines, 2 on one end, one on the opposite.
If you can see all the segments, than probably the zebra strip is the cause.
You might also turn on the meter, and scope the pcb gold terminals one by one to make sure there is signal there.
It woiuld be nice to have a decade resistance device to pad that channel..
True. Alot quicker. I can usually tell where to start based on the volume control value. 150k didn't do enough, 100 was close, 82k was about as close as I could get it
Hey Jordan enjoy your content sounds like you’re in Southern California somewhere have u ever mentioned what or where the shop is I’m having trouble finding a reliable tech in so cal I have a 70s kenwood receiver I’d like to have work done on u really look to be on the ball
I work for Classic Audio Repair Inc. look me up!
Thank you
Do you do services? I have a pioneer sx 1980 that needs a full restoration
Yep. Can service it. Just visit repairaudio dot com and call for an appointment