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one channel louder than the other in my vintage amp

cspyon

cspyon

AK Subscriber
Subscriber
Hi friends,

Before I drop it at the tech shop, I'd like to ask for your advice on my vintage integrated amp JBL SA600.
When I tested it, I heard the output from the left channel was much weaker than the right channel. I would say it's about 2 (left) out of 10 (right). The sound from the right channel just overwhelms the left when I set the volume at 9 o'clock onward. I made sure all the wires hooked up correct, and tested both on CD and records, but the outcome was the same. As this amp is more than 50 years old, it needs service, of course, but except for the unbalanced channel, it sounds just great. I opened the cover and cleaned some dust inside, including the volume control, but the problem is still there. Any advice or feedback appreciated much in advance.
 
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I second that advice. Over time, oxidation and crud can build up in the controls, leading to high resistance and poor conduction. Also, it is possible that a switch (like the input selector} has some issues at this age and fiddling with it just a bit can bring the channel back. playing with all the switches might reveal the culprit.

Good Luck

Shelly_D
 
Thanks much for your quick advice. Now, if you look at the pic attached, you see inside of the four switch pots, SELECTOR, TREBLE, BASS, BALANCE from the right. The pot on the far left is BALANCE control. BASS, TREBLE, SELECTOR works all right. Now, specifically which part of the pots need to be cleaned by contact cleaner like Deoxit? Can you point to that? Thanks.
 

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Thanks a lot for your advice.
Actually I tried dissembling the unit's faceplate to use the contact cleaner, but stopped the process it's rather tricky and complicated.
Let me take it to the tech shop for their professional work. Anyway it needs service.
 
My first thought would be the balance control. It's possible the volume control would contribute depending on what type it is. Beyond that it falls to the gain stages perhaps in the preamp or amp sections.
 
Thanks a lot for your feedback and advice. Actually I dropped it off at a local tech shop for repair.
Now, this is my simple question: Can this issue of volume unbalance be fixed?
As you know, this is a vintage unit produced in mid-1960s, and I'm a bit worried that if the part needed is proprietary and unobtainable. What do you think?
 
There are many modern day substitutes for old and now obsolete transistors and diodes. Some integrated circuits have become unobtainium but the most likely causes for this type of problem probably don't involve that.

Good Luck with it.

Shelly_D
 
cspyon said:
Thanks a lot for your feedback and advice. Actually I dropped it off at a local tech shop for repair.
Now, this is my simple question: Can this issue of volume unbalance be fixed?
As you know, this is a vintage unit produced in mid-1960s, and I'm a bit worried that if the part needed is proprietary and unobtainable. What do you think?
Click to expand...
It probably just needs cleaning, but if it's a problem with resistors or capacitors, replacements are available. If it's a problem with semiconductors, replacements or substitutes are generally available. If it's a problem with switches or variable resistors, replacements may be a bit more difficult but the originals can usually be repaired.
 
DaveVoorhis said:
It probably just needs cleaning, but if it's a problem with resistors or capacitors, replacements are available. If it's a problem with semiconductors, replacements or substitutes are generally available. If it's a problem with switches or variable resistors, replacements may be a bit more difficult but the originals can usually be repaired.
Click to expand...
DaveVoorhis said:
It probably just needs cleaning, but if it's a problem with resistors or capacitors, replacements are available. If it's a problem with semiconductors, replacements or substitutes are generally available. If it's a problem with switches or variable resistors, replacements may be a bit more difficult but the originals can usually be repaired.
Click to expand...

Hope the problem can be solved with just cleaning! Anyway I'm glad to hear that. Thanks!
 
shelly_d said:
There are many modern day substitutes for old and now obsolete transistors and diodes. Some integrated circuits have become unobtainium but the most likely causes for this type of problem probably don't involve that.

Good Luck with it.

Shelly_D
Click to expand...

That's great to hear! I look forward to good news from the tech shop where it's on their bench for repair.
 
To: cspyon.

Can you share with us as to what the problem was on your JBL amp?
I have the same problem with my Yamaha M-80 Power Amp.
My right channel is very weak vs. the left channel.
 
I have found this trouble too. I have the ATLP120USB. Whenever I record songs to Audacity (the software packaged with my turntable) the right channel was clearly not recording as high as the left channel. I was initially using the balance control on the software to fix it. But I found out something that made a night and day difference.
The way the cartridge sits in the headshell was making the stylus track at an angle, with the needle digging into the left channel. This made the left channel louder since it was not properly tracking the right channel. I had to end up shimming the left side of the cartridge until I could get the stylus tracking straight up and down in the channel. I found an old ebay gift card and cut a couple slivers off to fit under the headshell as seen in the attached picture.
I now have a way more balanced sound. Recording in Audacity, there is now barely any difference in the volume of the left and right channels. Listening closely in the headphones, the right channel sounds more prominent than before. That being said, make sure your stylus looks like it is tracking vertically in the groove. The manufacturer does not always build the system correctly. I did this without buying any expensive equipment. Just my trusty eyes and ears. ;)

IMG_2253

IMG_2253

  • Media owner rdkemp13
  • Date added
I cut slivers of an old ebay gift card to shim under the headshell to make sure my cartridge was...

P.S. the left channel on the record are the grooves closest to the spindle. The right channel are the grooves closer to the outer edge of the record.
 
have you tried changing the speaker wires on to another out put on the amp,
see if the problem follows the amp of speaker,
this might help to identify a problem in the amp or speaker if self
 
If its not something obvious like controls, switches, or cables, you might have some component going off value. I've run into bad capacitors in the feedback circuits causing uneven gain side to side.

Honestly very few things are truly beyond repair, unless its a failed component that is obsolete and can't be found. Whether its worth the effort of fixing is a completely different topic. I've fixed more than a few things that I should have just thrown away because I was bored. If I was paying to have it done a lot of it would have just gone in the trash.
 
cspyon said:
Hi friends,

Before I drop it at the tech shop, I'd like to ask for your advice on my vintage integrated amp JBL SA600.
When I tested it, I heard the output from the left channel was much weaker than the right channel. I would say it's about 2 (left) out of 10 (right). The sound from the right channel just overwhelms the left when I set the volume at 9 o'clock onward. I made sure all the wires hooked up correct, and tested both on CD and records, but the outcome was the same. As this amp is more than 50 years old, it needs service, of course, but except for the unbalanced channel, it sounds just great. I opened the cover and cleaned some dust inside, including the volume control, but the problem is still there. Any advice or feedback appreciated much in advance.
Click to expand...
May be failing output transistors or mismatched vbe hfe
 
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