What do you guys think? BS or Plausible....

[Transistorized]

Most of you guys know that recently I had to have a few potentiometers replaced on my recently acquired JVC RC-M90. Today I was about to install (for the first time in my ownership) 10 D Batteries and use it that way. After all, I have the rechargeable ones (10,000 mAh) so why not

With my Conion C-100F (due to the chrome brackets adding support to the box) I flip it over on the carpet or on my bed on its "face" to load the batteries. Out of habit I found myself about ready to do that with the M90 and I stopped myself. I started looking at the face of the machine and noticed that the switches and knobs all stick out past the "face" of the stereo. Unlike the Conion C-100 it doesn't have support brackets to keep the weight of the box off the dials and what-not.

This started a thought process because we all know how delicate these pots are on the M90.

Could it be that some of the damage of potentiometer fingers breaking loose within the pot could be done during battery loading and removal? It just doesn't seem healthy for them to have to support the weight of this huge box when loading batteries. I'm sure some have broken by use...some may have gotten bumped...but what do you guys think about the act of loading batteries if not done with the unit standing up?

I'm thinking it may be a better idea to load batteries standing up to better keep this issue from happening. This doesn't have to be limited to the M90 but ANY Heavy box not having brackets to support the weight when flipped over on its front.

BS or Plausible? Discuss....and be sure to include your opinion as to why you do or do not feel it matters.

Thx.

 

[Superduper]

No.

 

[Transistorized]

No.

Nice to know. Might be over-thinking this whole thing

 

[blu_fuz]

If you are rough with it, I'm sure it doesn't help. 99% of the time with my big blasters I will lay it face down on the bed then load it up. (like my women)

 

[Nickeccles]

Load up batteries on a bed.............I have broken pots in the distant past & it's a lesson you never forget

 

[Transistorized]

If you are rough with it, I'm sure it doesn't help. 99% of the time with my big blasters I will lay it face down on the bed then load it up. (like my women)

LMAO.....With Energizers Right? After all...they keep going and going and going

I got to thinking. You have to assert effort into pushing and pulling the knobs when you're removing and installing them so it might not be as bad as I was thinking. But that only raises another question. Why do they put protection brackets on boxes? Just to look cool, function or both?

 

[BoomboxLover48]

The spindle/axle of the pot has a lock on the groove that would prevent it push to the rear side. In the second picture on the right it clearly shows the lock on the spindle groove. All pots have that lock washer on the spindle/axle of the pot. After all one should not rest a box face down. Loading batteries can be done in standing position. Resting o a thick foam pad is not a bad idea because load can be evenly distributed.

 

[Transistorized]

The spindle/axle of the pot has a lock on the groove that would prevent it push to the rear side. That is what I remember. All pots have that lock washer on the spindle/axle of the pot. After all one should not rest a box face down. Loading batteries can be done in standing position. Resting o a thick foam pad is not a bad idea because load can be evenly distributed.

Hi BBL48. I have noticed a few pots having the threaded screws securing it to a metal frame for support. I see what you are saying about the C-clip to prevent back and forth movement. Looks like in that pot it rides in a slot. That's a great design. I think they all should have that. Goes to show there are many variations on design. Some pots may be more resilient than others.

I noticed on the M90 the pot case shaft is threaded but they do not make use of securing it with a nut or washer or clip. They only use a case "cage" that is crimped to the board to help secure it. The spindle shaft goes directly into the pot from the knob. Unless the lock ring is inside the case of the pot there doesn't appear to be any protection for that model which may be why they are more prone to failure especially when they wear because the shaft will actually rock not only back and forward but left and right. On my parts box you can rock the spindle back and forth and in and out (being it only slightly...but still). This has to create more and less tension on the sweeper fingers and the mounts that secure them. They're only held onto the plastic spindle base by tiny (and I mean TINY) melted and mushroomed pins.

I think I'm going to play it safe on the M90 and load batteries standing up. What's the worst thing that could happen with this idea? Maybe the batteries fly out before getting the battery door on? Rather that then to even remotely or possibly damage a pot that you can no longer get. Every one of my boxes seem to have a different design on the pots so I guess this may be a case by design or specific model.

 

[blu_fuz]

The nut on the potentiometer body doesn't protect the shaft from getting pushed in...... The shaft moves freely of the potentiometer body. The nuts only hold the pot and pcb secure to the chassis/radio case.

 

[Transistorized]

Hi blu_fuz.

Great pictures!! I noticed the back side of the shaft dial in the center is a small rear support post. Maybe this rests in a slot on the back of the case of the pot and limits its movement? Either way, I am sure that the plastic spindle has to wear over time increasing the chances of failure as it wears. 30 year old plastic...hmmm.

IDK. I just see it being bad idea for this model to apply any pressure to the pots. Maybe this advice will keep a few more boxes going by being more proactive than reactive about this and draw awareness to the issue even if it seems a bit nit picky.

Guess that's just how I am.

 

[-GZ-]

No.

That made me chuckle. Norm's shortest post ever.

 

[Superduper]

That made me chuckle. Norm's shortest post ever.

Wasn't much to say. A succinct answer to a very specific question was all that is needed. I have already seen these pots failing in M90's for several years now, on several examples. The failure is in the nylon rivets breaking off very similarly to the M70 Alps slider feelers. Most likely this is due to several factors: 1: Nylon shrinks over time resulting in a looser fit between the rivets and the feeler holes resulting in fatigue breakage over time. 2: The increased usage of deoxidation solutions on these older gear might contribute to deterioration of the plastic parts faster than if they were not used and 3: loss of lubrication on both shaft and feeler/resistor areas might contribute to a generally "rougher" motion that further compounds the problem. Once the rivets are loose, it's not a matter of if but when they pots will fail. If the pots are still serviceable but the feelers are loose, then their life can be extended by promptly servicing them via gluing the feeler to the nylon block as well as the nylon rivets areas with plastic superglue to eliminate play. Once the feelers detach completely, then the chances of a successful repair diminishes significantly. It's extremely difficult to realign the feeler to the original mounting points and without the rivets, it just won't be as strong of a repair. One should keep in mind that the alignment is critical to proper operation, otherwise you will get weird operation results. For example, seeming proper operation on the lower range of operation but loss of balance control and stereo when knob approaches higher range.

As for laying the boombox on it's face, I'm presuming you aren't hammering the knobs with a ball peen hammer. So normal handling isn't going to break those pots. Understand that up until just a few years ago, broken M90 pots were virtually unheard of. Only recently with all the M90's approaching the same age are we now seeing this phenomenon. In fact, if you were to search the archives, you will find at least 1 thread by me speaking to this M90 pot issue. So unless nobody until recently changed batteries on an M90, then why in the world would it suddenly only become a problem now? Age, that all, plain and siimple. As well, if you look at how the pots and the feelers detach, then you'll understand that while you can certainly damage a pot, or a switch, or a grill by abusive handling, just simple normal handling by placing it on it's face isn't going to cause those feelers to detach. Furthermore, the knobs themselves will bottom out and prevent further inward motion of the shaft once the back face of the knobs contacts the front cover.

 

[trippy1313]

Hahaha. Duh.

Actually I had no clue, nothing new. But now I do.

 

[Transistorized]

As for laying the boombox on it's face, I'm presuming you aren't hammering the knobs with a ball peen hammer. So normal handling isn't going to break those pots. Understand that up until just a few years ago, broken M90 pots were virtually unheard of. Only recently with all the M90's approaching the same age are we now seeing this phenomenon.

That is an interesting point Superduper and Thanks for your input. It makes sense Oh and No sir. No Hammers better ever come close to my box and I for sure don't do this when replacing batteries :judge:

I am sure lots of folks have replaced batteries laying the box face down throughout the years with no issues and may get by doing it today however, (as you said) now that we are starting to notice that these are becoming more prone to failure with age/use, maybe what used to be acceptable may now require some reconsideration. This decision is entirely up to each owner. This post was more for those who may have never given this any thought (which applied to me before this post). Obviously nothing will last forever and I am in no way trying to persuade anyone to change their behavior with their current routines. Its your money and your box and your decision as to whether you feel this could benefit you or not.

Thanks to all of your replies on this I have a better understanding and feeling of my own on this subject and I have enjoyed hearing from you guys. Interesting points on both sides have been raised. I now know that not all stereos pots are as susceptible to this as the M90. For the M90 owner you may want to be more careful than years ago Father time affects us all and as a result we sometimes need to change our behavior to protect what is now known to be more delicate than it used to be (IMO).

So...from what I've seen in this post (about the M90 in particular) I'll avoid any unnecessary pressure being placed on the pots by keeping my box standing up at all times. Couldn't hurt right? After all, if laying on it's face supposedly won't hurt anything it then it stands to reason that Not laying it down (as a precaution) definitely wont. Other than being slightly more difficult to load batteries I can't come up with anything Negative about this. That I can live with

 

[redbenjoe]

i use a big cushee pillow --box goes face down --easy to load batteries- never a problem

 

[BoomboxLover48]

i use a big cushee pillow --box goes face down --easy to load batteries- never a problem

Me the same! Memory foam pillow!

 

[Ken]

No.

The Boomboxery Gods don't mess around. They cut to the chase. Busy fellows.

If you are rough with it, I'm sure it doesn't help. 99% of the time with my big blasters I will lay it face down on the bed then load it up. (like my women)

See #1. My preferred method, though.

i use a big cushee pillow --box goes face down --easy to load batteries- never a problem

Experience is always key. You can't be too careful with your pride & joy, to paraphrase Stevie Ray. ​

 

[crazygamer]

I´ve also thought about it, pots probably get damaged in case the box tips over to the front, this might result with damage. My battery loadings are always done on bed or mattress, but i don´t have such biggies anyway so there´s nothing to worry about for me