Line in issue on Sanyo

[Jboulukos]

I’m playing a belt-driven turntable through my Sanyo m-x650k and am having various sound quality issues. At first, while in Stereo setting, the R channel didn’t work and was buzzing. I cleaned out the red and white ports from the back with contact cleaner and cotton swabs and used contact cleaner again on all knobs including bass, treble, balance, volume, as well as the switch for the mono/stereo/expand control. This resulted in both channels playing on Stereo setting, however the quality of sound seemed inconsistent. Sometimes the bass would leave completely, or the other channel might not work, or various other responses that are either difficult to describe or I forgotten about. Is this a matter of continuing to use contact spray and overtime will get a better sound? Or is this more than just the contacts? Not sure how to start diagnosing this issue. After attempting another cleaning, the R channel is not working in stereo again.
Other info:
- I have used another turntable on the line-in and had the same results.
- I have no issues with both channels in stereo using the cassette deck and no issues with Radio, also no issues with the bass, treble, balance and volume while using radio and cassette.
-buzzing in the R channel will increase or decrease with manual rotational movement of the red cable, and sound quality will worsen in the L channel with manual rotational movement of the white cable from the back of the radio at the line-in ports.
Any information is much appreciated.

 

[Superduper]

Sounds like a more thorough cleaning of all the switches, controls & contacts are in order.

 

[Jboulukos]

Sounds like a more thorough cleaning of all the switches, controls & contacts are in order.

Thanks for the reply. I did all the switches and knobs and even the ports in the back of the boombox. Tried playing the turntable again. This time after about 5 minutes of fiddling with the red and white cables, and with the balance knob, the Stereo setting played both settings. So I guess it needs more and more cleaning. Or maybe I just have a low quality contact cleaner that I purchased here in Colombia. Maybe I need to spray the crap out of these switches even more than I already have?
Bass is a little lacking with this Boombox and I’m suspecting it may be from the absence of the inner divider/baffle between the two woofers. I noticed other people having the same model with an inner baffle when showing videos of the dismantling of the boombox. Any thoughts on how to get more bass? Or even how to make another baffle?

 

[Superduper]

Well, first off, if you are merely spraying from the outside of the boombox, that is not the recommended process. The contact cleaner will likely get everywhere and migrate to areas internally where it is not desired. Secondly, there are switches inside that you simply can not access from the outside. The most important is a long rectangular bar (record/playback switch) which is usually mounted directly on the main printed circuit board and tripped by the action of the tape deck. All the audio signal travels through that switch. Inside, you will be able to see the actual switches and controls too, not just the knob or shaft. In most cases, those switches or controls will have a small access hole that you can spray the cleaner directly into. Soak up any excess.

 

[Radio raheem]

most of these boomboxes were not bass monsters, i have the jvc m90 and love them but there not bass shakers, if you want bass buy something like a jvc kaboom mate

 

[Jboulukos]

Thanks for all the great input. Yes, I have cleaned the dials and switches and record bar from the inside. And now I’ve done it twice. Soaking up the excess. I still have the same issue. The red port on the line-in/phono-in doesn’t seem to work consistently. And when it does, it makes both channels sound poor. Sound quality is better when the red is not working with the R channel out and the Left channels producing sound. Again, no issues with radio or cassette sound. Can it be possible that the red port needs to be changed or something? I know this isn’t a hi-fi stereo and I
should not expect excellent sound but something isn’t working correctly for the line-in. I had an issue like this on a vintage receiver once, did all the contact cleaning but it didn’t resolve and brought it to a technician. I just don’t remember exactly what he replaced though. Is the only issue the cleanliness of the pots and switches and record bar? No other possibilities for this to be failing?

 

[Reli]

Since you say there's no problem when you use the Tape or Tuner, I don't think the problem is with the knobs or the Record Bar.
Check the "Function" switch again. Where did you put the straw when you sprayed it?
Also, check the Line In ports connection to the circuit board --- Make sure that any solder joints there are still good. And clean the Line In/Phono switch next to the ports.
Also, some cables are low quality junk. Try a different cable.

 

[Superduper]

The ports (rca jacks) are soldered to the pcb and due to the force of inserting and removing the plugs, especially when the jack finish is no longer smooth, can and often do cause the solder connections to fracture resulting in poor or unreliable signal connections. To fix, you can usually reflow the solder joints, ideally adding some fresh solder.

 

[MisterFelix]

Properly cleaning the function switch is critical on nearly all boomboxes. Another switch to check and clean on the Sanyo m-x650k is the Line In/Phono preamp switch on the back directly under the ground screw. Both left and right channels pass through this and a dirty switch could cause problems with one or both. When trying different turntables be sure to connect the ground wire to the ground screw. Some turntables like the PS-Q3 in the picture do not have a ground wire. This could contribute to your hum problem.
Also - many folks who were not around during the 70s and 80s are unaware of the need for preamplification on turntables from that era. Many just plug the turntable into the line in and expect it to work like an iPod or CD player. Luckily your Sanyo has a built in phono preamp and should be able to handle most turntables - just flip the switch to phono when using an old school turntable. To my generation this is obvious, but younger folks often miss this.

 

[Jboulukos]

Since you say there's no problem when you use the Tape or Tuner, I don't think the problem is with the knobs or the Record Bar.
Check the "Function" switch again. Where did you put the straw when you sprayed it?
Also, check the Line In ports connection to the circuit board --- Make sure that any solder joints there are still good. And clean the Line In/Phono switch next to the ports.
Also, some cables are low quality junk. Try a different cable.

Nice info! Thank you! I will check the function switch/dial. I believe I originally sprayed in the shaft with the cover off and underneath the face of the radio station selection. I took a pic of the line in area from within, although I think it would be best to take the radio and cassette off their posts and examine the area.

Maybe just remove old solder and add new solder. The cables are original Sony attached to the turntable I’m playing. And I’ve tried another turntable with attached cables and received the same issue. When I was cleaning out the line in ports with cotton swabs, I noticed the red inner plastic cylindrical part spinning inside the metal port and the white port doesn’t do this. I circled the port that doesn’t seem to be doing it’s job.


As you can see the ports are shared with a switch for “line-in” and “phono-in” and I have tried to use the connection for both. Sound for the turntable only works with the switch on phono-in as it should. Should that little switch be spray cleaned?
Thanks again for the input. I’m willing to do anything to get to the bottom of this.

 

[Jboulukos]

Properly cleaning the function switch is critical on nearly all boomboxes. Another switch to check and clean on the Sanyo m-x650k is the Line In/Phono preamp switch on the back directly under the ground screw. Both left and right channels pass through this and a dirty switch could cause problems with one or both. When trying different turntables be sure to connect the ground wire to the ground screw. Some turntables like the PS-Q3 in the picture do not have a ground wire. This could contribute to your hum problem.
Also - many folks who were not around during the 70s and 80s are unaware of the need for preamplification on turntables from that era. Many just plug the turntable into the line in and expect it to work like an iPod or CD player. Luckily your Sanyo has a built in phono preamp and should be able to handle most turntables - just flip the switch to phono when using an old school turntable. To my generation this is obvious, but younger folks often miss this.

More great info. I will attempt cleaning the tiny line-in/phono-in switch as you said. And yes, I was thinking of the ground too! The ps-q3 and q7 don’t seem to have grounds like 70s turntables, maybe because they were part of a component system that had a ground. I ordered a ground loop insulator from amazon and it’s in the mail. Maybe that can help with the lack of ground.

 

[Radio raheem]

that phono line in switch should be flooded mate, it's probably you're issue, i go through spray like water lol but leave it dry for a good few hours bud

 

[Reli]

Should that little switch be spray cleaned?

Definitely. Also, try a different cable. I'm serious, I've had a couple low-quality cables that couldn't maintain consistent volume. I had to twist and turn them to get full volume.
And regarding the "Function" switch on the front, don't bother spraying unless you can actually see the metal contacts inside the switch. Just spraying the black nylon lever isn't going to work. You need to be able to see the copper feelers behind that lever.

 

[Radio raheem]

also spray the phono sockets themselves...kill that box with spray lol

 

[Jboulukos]

I actually sprayed the switch in the back for the first time and worked it back and forth and resulted in both channels working for a bit. Changed a record and immediately went back to 1 channel. Checked the switch and it was harder to move back and forth, requires more force now.

 

[Radio raheem]

If the switch is way to stiff i would use a bit of wd40 on it that happened to an m90 years ago when i sprayed it with contact cleaner and the switch went so stiff it actually snapped so way more contact cleaner and a little wd40 is recommended by me but don't use wd40 anywhere else.....now i will be banned for recommending it lol

 

[Jboulukos]

If the switch is way to stiff i would use a bit of wd40 on it that happened to an m90 years ago when i sprayed it with contact cleaner and the switch went so stiff it actually snapped so way more contact cleaner and a little wd40 is recommended by me but don't use wd40 anywhere else.....now i will be banned for recommending it lol

Best way to spray the little switch? From the outside? Or if from the inside, then where? today I sprayed it for the first time and only from the outside on both sides of the switch and moved the switch back and forth. It’s super stiff now.

 

[Jboulukos]

Update: I found that when I remove the cables from the rear, I need to put them in red first then white in order to get both channels to work. This procedure has to occur following flipping a record or changing to a new record. Not normal but it works. It makes me wonder if the sound quality could improve if this was fixed somehow. The order of inserting the red and white cables shouldn’t dictate whether or not both channels produce sound.
Also makes me think of the ground again. I’ll have more info when I apply the ground loop insulator also.

 

[Radio raheem]

Best way to spray the little switch? From the outside? Or if from the inside, then where? today I sprayed it for the first time and only from the outside on both sides of the switch and moved the switch back and forth. It’s super stiff now.

on the m90 i sprayed it from the outside Sir but sometimes you may have to do this several times, honestly i have used a hole can on one box before but im sure you won't need to do that and most wouldn't recommend that

 

[Bru87tr]

Buy some crc 2-26 multi-purpose precision-lubricant, it works very well.

Plastic safe too.

Also, as SD said, I would do this. "To fix, you can usually reflow the solder joints, ideally adding some fresh solder".