Open it for fix or no?

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grig15

grig15

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Jun 22, 2018
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Hello!!!

I have some awesome looking JVC 838. It is very mint looking. But sorry for this unit fans I don't like it as much as the other mid sizes that I have, and want to sell it. But the problem I cant decide to open it and try to fix the unit or leave it to more professionals and sell as it is. So I will try to explain what is wrong with it, and you suggest me to open for fix or no.


Problem 1: Stereo/mono switch
The radio is working good, but when Im switching it from mono to stereo position, it loses sound in one of the speakers, when Im playing with the switch I can get sound from both speakers. But in the biphonic mode it is sound very bad and low volume.

Problem 2: Cassette deck
When I push the button, cassette deck is opening very slowly (it must be easy fix, must be oiled I think). When I push play, it is trying to play slowly for 1-2 seconds and stops (relising play button like autostop).

Problem 3: Strange glue or something like that on cassette deck door (see photos)
When I looked under the tape sticker, it is some strange glue like something, and scratches (not sure). Can you help me to identify can it be some stock glue?, or it is something that happened after that by owner or etc... This is strange because overall it is very mint, why must cassette deck be that kind of destroyed I don't understand. And should I try to clean it with something like alcohol?
And Im also interested how much will be approximate price difference for working unit and not working unit?

Hoping for help and suggestions.


Thanks
 

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Hisrudeness

Hisrudeness

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That’s looks pretty good. Like JVC 550’s half the fun is trying to find one that’s not to dinted up on top.

I have a soft spot for these. The styling is bold but classic and in my opinion yours is a good example and worth the effort to restore. The Biphonic thing is weird but that’s part of the charm of the box. As far as worth, I’m not sure as the EBay prices have muddied the waters. I paid £110 for mine but that was many years ago.
 
T-STER

T-STER

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Jul 14, 2014
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Yeah this is worth a fix if you have some minor technical skills.

The deck will need a full overhaul, new belts, possibly rollers, lube etc and it will probably be fine.

Stereo switch could be as simple as some deoxit needed although i have a similar problem on one of my Sharps and have not been able to solve it. One of the better tech guys will chime in on this im sure.

Deck door may clean up with some isopropol if its glue residue or finding a new door shouldnt be too bad with some patience.
 
Hisrudeness

Hisrudeness

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T-STER said:
Yeah this is worth a fix if you have some minor technical skills.

The deck will need a full overhaul, new belts, possibly rollers, lube etc and it will probably be fine.

Stereo switch could be as simple as some deoxit needed although i have a similar problem on one of my Sharps and have not been able to solve it. One of the better tech guys will chime in on this im sure.

Deck door may clean up with some isopropol if its glue residue or finding a new door shouldnt be too bad with some patience.
Click to expand...
Yeah that glue doesn’t look original. Looks like cement style or something. A pity about that.
 
Superduper

Superduper

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The glue is probably due to someone trying to stick that sticker on, whether to reaffix an original or glue on some kind of repro. It’s going to be hard to get the residue off without damaging the base material.

The stereo switch issue could be needing cleaning or it could be more problematic (bad slide control which has lost one channel). The reason you can get both speakers in biphonic or expand but not stereo is because the system mixes the channels in those modes (but not stereo) which occurs after the slide controls but before the amp. If a cleaning of the stereo mode switch doesn’t clear that up, then there is a strong possibility of failed sliders and the issue probably affects up to 1/3 of the 838’s out there.

If you are wondering whether you can get more money (net) from selling it before/after repair, and you are going to pay a professional to get it repaired, most likely best to sell it as-is. If the stereo switch merely needs cleaning, maybe you break even but if one (or more) of the slide switches need repair or replacement, then the bill might be high, or worse, the technician might refuse to repair it since those slide controls are no longer available. In that case, the box won’t be 100% fixed but you will still need to pay for diagnostics to get it back.
 
grig15

grig15

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Jun 22, 2018
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Thank you very much for response! I will notify about updates.


Superduper said:
The glue is probably due to someone trying to stick that sticker on, whether to reaffix an original or glue on some kind of repro. It’s going to be hard to get the residue off without damaging the base material.

The stereo switch issue could be needing cleaning or it could be more problematic (bad slide control which has lost one channel). The reason you can get both speakers in biphonic or expand but not stereo is because the system mixes the channels in those modes (but not stereo) which occurs after the slide controls but before the amp. If a cleaning of the stereo mode switch doesn’t clear that up, then there is a strong possibility of failed sliders and the issue probably affects up to 1/3 of the 838’s out there.

If you are wondering whether you can get more money (net) from selling it before/after repair, and you are going to pay a professional to get it repaired, most likely best to sell it as-is. If the stereo switch merely needs cleaning, maybe you break even but if one (or more) of the slide switches need repair or replacement, then the bill might be high, or worse, the technician might refuse to repair it since those slide controls are no longer available. In that case, the box won’t be 100% fixed but you will still need to pay for diagnostics to get it back.
Click to expand...
I have JVC M70 for parts, can I found similar switch in m70?
 
Superduper

Superduper

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I'll have to check to see if the M70 and 838 taper and resistance values are the same or not. Get back to you about that. Usually, the feelers inside the controls break off and if not lost, can be reaffixed by taking the controls apart. If they are lost, then the feelers inside the JVC M70 controls are the same and can be cannibalized to repair. During repair, DMM the traces to make sure they are not broken, which happens in about 40% of the broken sliders. Physically, I think the bass and treble sliders might actually transplant (again, I need to check to see if the specs are the same or not) but there is no M70 equivalent for the balance slider on the 838.

One word of advice regarding the 838. Regardless of whether you or your tech performs work on the tone board, make absolutely sure that the main and tone boards are desoldered first BEFORE attempting to unscrew and remove them from the chassis. These two boards are soldered together along an edge, probably 20 or 30 pads to desolder. Those are not structural joints and any attempt to remove the boards together while tethered will almost certainly result in the pads and traces and solder joints getting broken. More than 1 member has, for whatever reason, did exactly that. Once the solder pads and traces lift and pull off, any repair will look awful and appear to be a hack job. If you were to resell it later like this and the buyer removes the back cover and sees the mess, he/she likely won't be very happy with it. Just fyi.
 
Superduper

Superduper

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Looks like one slider from an M70 is compatible with the RC-838 but the other is the wrong taper: A vs B. I think the compatible one will be the bass slider. The balance slider of 838 (also a commonly failed component) has no equivalent on the M70. Also, the volume controls are totally different so those are not interchangeable either. The best thing to do is to rebuild them using bits from a donor slider. The internal feelers (there are L and R oriented ones, not swappable) are generally interchangeable on all the alps sliders except on the 838 volume control which I've never looked inside of because I've never seen one of those that failed yet, clearly a better design on that component than the other ones. Understand that in general, the original repair path has always been to replace those sliders when they failed. Only in recent years that they are no longer available from JVC are we contemplating disassembling and repairing them, as it is the only way to keep these running. However, not all techs will do that.
 
grig15

grig15

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Jun 22, 2018
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Superduper said:
Looks like one slider from an M70 is compatible with the RC-838 but the other is the wrong taper: A vs B. I think the compatible one will be the bass slider. The balance slider of 838 (also a commonly failed component) has no equivalent on the M70. Also, the volume controls are totally different so those are not interchangeable either. The best thing to do is to rebuild them using bits from a donor slider. The internal feelers (there are L and R oriented ones, not swappable) are generally interchangeable on all the alps sliders except on the 838 volume control which I've never looked inside of because I've never seen one of those that failed yet, clearly a better design on that component than the other ones. Understand that in general, the original repair path has always been to replace those sliders when they failed. Only in recent years that they are no longer available from JVC are we contemplating disassembling and repairing them, as it is the only way to keep these running. However, not all techs will do that.
Click to expand...
Thank you very much for such beautiful and detailed reply. But as much you informing me, more Im afraid to open it. Because Im not sure that my skills will let me open the switch and accurately repair it. Don't want to ruin beautiful box. Better to sell how it is, so the new owner can repair it and enjoy. I want to get some good m70 in place of this.

Thanks again for great help.

Reli said:
That sticker is awesome. Protect it at all costs.
Click to expand...
Reli said:
That sticker is awesome. Protect it at all costs.
Click to expand...
Reli said:
That sticker is awesome. Protect it at all costs.
Click to expand...
 
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