JVC PC 11 Compo tape deck grounding cable – where does it go?

[dubout]

I had issues with inconsistent speed when playing a tape. Also it would only wind forward even if you press the rewind button. I took it apart and found that a component of the mechanism was broken. It took me a few days and now, when wanting to put it back together, I can't remember where the black grounding cable was attached. Yeah, I know, stupid me ... I should have taken pictures.

I remember that on one side it is attached to the board. But on the other side it might have been attached to the frame of the tape mechanism or the small frame of the mic / mix mic / mic attenuator.

Can anybody give me a hint where the grounding cable has to go?

 

[Valde]

I can check it for you, just need to do an unboxing first

 

[Valde]

And here is the answer, the ground wire should connect to the frame of the transport. Do you by any chance have the service manual for this box?


Same part broken in your box? The one i got looks as unused as an 38 year old box can do, but still this pice of plastic is broken.

 

[dubout]

Wow, nice first picture Thank you so much! This is really of great help

Yes, it is the same part that broke at the same place in my box. I glued it yesterday with something that would translate to 'weld seams' and put in the spring, it still holds. I hope the glue holds up to its name.

Sadly I don't have a service manual. I googled quite a while but had no luck. This box seems to not have as many fans as the PC-5 Compo. I also think the bass could have more punch. But it is a very detailled and clean sounding box which I like alot.

Time to close the patient up!

 

[Valde]

I glued the plastic pice with "Loctite precision max" and wrapped it in polyester line for extra strength. I hope our glued plastic parts stay together! I have not used the PC-11 before, just tested it when i got it. "Unboxed" it today to check the ground wire, and had to fix it when it already was on the bench I like the tape deck, quality is way above average boombox quality (not the plastic). I checked the speakers and the souround is probably harder than the cone itself Maby because my box has been in storage sins early 90's? As you said, the sound is good, but missing some bass. Maby the souround will soften with use and the bass will be back

 

[floyd]

These are Kick-Ass Boombox if you invest in a pair of 5 inch car speakers and put them in the boombox it would be surprised how it sounds.

 

[Valde]

These are Kick-Ass Boombox if you invest in a pair of 5 inch car speakers and put them in the boombox it would be surprised how it sounds.

I like the look of the original speakers, but the sound could definitely been better. I did an power messurment of my PC-11, and for a boombox, it got power. Messured one channel Watts RMS @ 4ohm before clipping, 1kHz signal. Line voltage 243VAC.
Voltage selector switch set to 240V - 12.56 Wrms@ 4ohm
Voltage selector switch set to 220V - 14.82 Wrms@4ohm
I wouldn't recomend to run any boombox with the voltage selector in the wrong position, this was just for the test.
The PC-11 definitely got bridged amps, and can deliver some power to some descent speakers
Note!
Newer change the voltage selector with the boombox plugged in.
Never do this if the options is 220/110
Of course everybody in here knows this

 

[dubout]

Thanks for the technical details, Valde. I like the look of the ceramic speakers, too. It was an innovation back in '83 and maybe they sounded better when they were new?
Listening to electronic music I notice that you can hear all low frequencies, they are not cut out. They just lack the warmth and the punch. I first thought the boombox sounded tinny. But after a while I started to get into the way it sounds. It's not tinny at all. Plus it sounds fantastic at very low volume.

If it was my every day system I would consider JVC Floyds idea because I think he has a point. But with my occasional listens I like to keep it original. Custom changes on boomboxes often are a one way street.

 

[Valde]

I guess the speakers sounded better when new. They got cloth sourounds with some kind of coating that probably have hardened over time. Used it all of yesterday incuding six hours outside at high volume and concluded that I keep the original speakers. I got other boxes if I need lot's of bass. Maby soften or change the souround one day? Impressed by the sound quality, bild quality and the tape deck.

 

[Arbusto67]

Ok, this is an old thread but I stumbled in it and have to say that I acquired a PC-11 some months ago: the unit was in good gonditions, save for a corner in the right speaker caused by a not exceptional packaging, but it only works with an external power supply, even checked the fuse but it was good, was unable to understand why the embedded power supply is not working. I am commenting here because I noticed that the speaker surrounds were very stiff, almost like cardboard, and I read somewhere that the treated cloth surrounds can be softened with brake fluid. So I bought the cheaper brake fluid bottle that I could find and treated the surrounds using a q-tip, WOW, this made a big difference, now the cones can move freely and the sound considerably improved in the bass area.
In the end a very nice boombox, shame for the non working embedded power supply, do you guys have any idea about that?

 

[dubout]

I can only guess but the power supply problem could have something to do with the barrel plug. It sits beside the cable plug and maybe power supply and barrel plug are linked. Maybe it has corrosion or dirt and doesn't lead through. The cables from the battery pack go directly to the board, that's why they work. I had a faulty barrel plug once. It was broken inside and I had to jump it with a cable.

I never heard about brake fluid treatment for speakers. I understand that you only put it on the rubber surroundings and not the cone? And do you just leave it there? I would love to try but I am worried that it degenerates the rubber and destroys the surrounding over time.

Maybe one can treat other rubber parts like pinch rollers etc. with that method. Does anybody else have experiences with this and can say something about the long term effects?

 

[Arbusto67]

I did the brake fluid trick about one month ago or a bit more and yes, I only treated the surround, not the cone, all seems to be ok, you leave it there in a thin layer and the fluid gets absorbed by the surround. Thank you for the suggestion about the barrel plug, I'll investigate further.

 

[dubout]

I did the brake fluid trick about one month ago or a bit more and yes, I only treated the surround, not the cone, all seems to be ok, you leave it there in a thin layer and the fluid gets absorbed by the surround. [...]

[...] treat the cloth surrounds with brake fluid. It may seem odd but I used this method on the woofers in my JVC PC11, [...] after a couple passes with a q-tip wet in brake fluid [...], now the cones are free to move and the sound improved a lot. Consider that I did this 5 or 6 months ago and the surrounds are still OK, so no harm to them.

I wanted to give an update to the brake fluid treatment as Arbusto67 encouraged me to try it on my JVC PC11.

I treated the surrounds with DOT 4 brake fluid four times in the course of two days. It worked well and the boombox now sounds smoother and bass is more present. It still doesn't thump which seems self explanatory considering the size of the speakers, the time it was built and the age. But for a 5 Euro investment with no hassle – as the grills come off very easy –, it was worth a try.

I read on different forums and there are a few things to bear in mind. I can't give detailed explanations, though. (I flew over most texts, english isn't my native language and I am not a technician.) So take these tipps with a question mark and as a starting point for your own investigation.

- This only works on artificial rubber not on natural rubber. Natural rubber could be dissolved.
- Don't use this on foam surroundings as they would dissolve.
- Brake fluid DOT 3 is ok, DOT 4 is recommended, DOT 5 doesn't work.

In fact, I would only try this on speakers others already had their experiences with or where it doesn't matter if anything goes wrong.