JVC AX-R97 sound issue
- Thread starter pioneer07
- Start date
-
- Tags
- ax-97 fuse lamps jvc jvc ax-r97
pioneer07
Member
I finally got some "real" speakers hooked up to this unit and I noticed the right channel is a bit louder than the left channel. I have to turn the balance knob to about 10 o'clock to get the two sides balanced. It wasn't that noticeable with bookshelf speakers that were closer together. Once I noticed it, you can also see it in the level meters on the front. The right side level goes a tick higher than the left.
I went ahead and replaced the rest of the capacitors on the main board. There were only 10 left I hadn't done and they were easy to get at. But that did not fix the issue. There are at least 5 more that I'd like to replace, but they are harder to get at. They are on the PCB that has the balance knob and loudness switch among other things. In the manual it's called the "Source Select & Level Indicator" PCB, and it's number is ENE-053-02. I see there are some black "pegs" that push in holding it on. I couldn't figure out how to pull off the knobs and remove the switch so I could back out this board to get at the parts. I didn't want to force it and risk breaking something.
There are also some additional ones on the board that's over on the side, which has multiple sub-boards on it. I replaced a few of the larger capacitors on that one, but haven't done all of them. I think that one is less likely to impact this issue, but who knows.
If it's not a drifted capacitor, I'm not sure what else it could be. There is no distortion, which is why I don't think it's a transistor. With some proper speakers it sounds really nice other than this balance issue.
I went ahead and replaced the rest of the capacitors on the main board. There were only 10 left I hadn't done and they were easy to get at. But that did not fix the issue. There are at least 5 more that I'd like to replace, but they are harder to get at. They are on the PCB that has the balance knob and loudness switch among other things. In the manual it's called the "Source Select & Level Indicator" PCB, and it's number is ENE-053-02. I see there are some black "pegs" that push in holding it on. I couldn't figure out how to pull off the knobs and remove the switch so I could back out this board to get at the parts. I didn't want to force it and risk breaking something.
There are also some additional ones on the board that's over on the side, which has multiple sub-boards on it. I replaced a few of the larger capacitors on that one, but haven't done all of them. I think that one is less likely to impact this issue, but who knows.
If it's not a drifted capacitor, I'm not sure what else it could be. There is no distortion, which is why I don't think it's a transistor. With some proper speakers it sounds really nice other than this balance issue.
pioneer07
Member
Just thought I'd share this if anyone else runs into this issue. Before I really dug into troubleshooting, there were some additional capacitors in the main signal path that I could replace. I hadn't done them because they were hard to get at. They were C401, C402, C403, C405 and C407. They are on the ENE-053-3 board. I had to remove the front face, the eq board and assembly, volume knob, etc to get at these. Also, these 5 capacitors (as well as a few I didn't replace on that board) are special "shorties". Normal size capacitors might not fit. I got around this by leaving extra wire length and bending them sideways. This seems to have fixed the balance issue! I also hit the balance knob with some deoxit for good measure since I hadn't done that yet. If there is a difference between the two sides now, it's so small I can't really notice it now (with my ears or visually on the meter).
I also replaced C345 and C346 on the board that runs along the side. I'm not sure if those would have anything to do with this issue but they were easy to get at. The phono preamp circuit is over on that board, too, and it's located right near the very large heat sink in this unit. I haven't really tested out the phono input yet. But I would not be surprised if I had to replace those due to being near that heat all these years.
I also replaced C345 and C346 on the board that runs along the side. I'm not sure if those would have anything to do with this issue but they were easy to get at. The phono preamp circuit is over on that board, too, and it's located right near the very large heat sink in this unit. I haven't really tested out the phono input yet. But I would not be surprised if I had to replace those due to being near that heat all these years.
pioneer07
Member
I have been using this one for a while now and I really like it a lot. There is one nagging issue. The right channel is about 2 to 3dB louder than the left channel. I have gone through this thing twice and all voltages are quite even between the two channels. Simply dialing the balance more to the left isn't a great solution because it reduces overall volume by quite a bit. I have to dial the balance over to almost 9 o'clock to get them equal.
I suspected it could be the balance pot itself, so I started playing with that. Weirdly, I can get this issue to go away for a while if I work the balance knob back and forth through the full range several times. After that, the issue will go away for a while but over time it will gradually drift back so the right is louder than the left. I don't think the issue is the master volume pots because when I have this unit working correctly, the volume turns up and down very equally.
I don't think I have tried Deoxit on this balance pot yet because there is no "crackle" or anything when I dial the balance knob back and forth. Any other suggestions beyond that?
(I hesitate to use Deoxit because a) one time Deoxit wore away too much of the wiper and I had to replace the pot and b) an expert told me WD-40 is a less abrasive alternative and usually does the trick)
I suspected it could be the balance pot itself, so I started playing with that. Weirdly, I can get this issue to go away for a while if I work the balance knob back and forth through the full range several times. After that, the issue will go away for a while but over time it will gradually drift back so the right is louder than the left. I don't think the issue is the master volume pots because when I have this unit working correctly, the volume turns up and down very equally.
I don't think I have tried Deoxit on this balance pot yet because there is no "crackle" or anything when I dial the balance knob back and forth. Any other suggestions beyond that?
(I hesitate to use Deoxit because a) one time Deoxit wore away too much of the wiper and I had to replace the pot and b) an expert told me WD-40 is a less abrasive alternative and usually does the trick)
NO NO NO!! Not regular WD40!! There is a specialist WD40 for cleaning electrical contacts. You should try to isolate the balance and maybe the volume pots. Use and Ohmmeter to see if they track the same. Maybe use 2 meters!
pioneer07
Member
I was always told that regular DeOxit was for on/off switches and selector switches. And Fader Lube was for pots. In fact, I think it was folks on this forum or AntiqueRadios forums who told me that.
Again, the dude who told me WD-40 was OK is a guy who specializes in rebuilding old pots from old equipment. He does hundreds of them.
In any case, I didn't use any WD-40 or anything else on this unit yet. I just worked that Balance pot back and forth several more times and the issue seems quite a bit better now.