It ain't bust, but I'll fix it anyway... JVC R-S7 receiver OR ' I just can't stop tweaking'

[yewneek]

Idle thumbs and the devil's work....

I just can't stop tweaking. However much it works, it can always be better. Right?

I've already got, but not yet replaced, the main filter caps for my JVC R-S7 receiver. Upgrading from 8700uF to 10000uF as I can't find the right value that physically fits. I've also got replacements for the rectifier diodes. Specifications met or exceeded.
I've gone with Nichicon FW as they're the ones that came up as suitable for specs and fit. £10 total give or take, another £15 for shipping. Not using Digikey again!

Anyway, what are thoughts on replacing the rest of the electrolytic capacitors?

I'm leaning away from touching the tuner section, but quite happy with the main amplifier, preamp, and phono sections recap. I don't fancy re-aligning the tuner section.
Just going by the Service Manual and making a list, there's 51 electrolytics to replace, but that's including the tuner stage, which I will edit out later when I inspect it internally to confirm.

It's not a rare beast by any degree, and there's plenty around on fleabay. I like it enough to want to bring it back to spec and use much improved modern components.

Thoughts welcome!

GB

 

[AnalogSteph]

This receiver is hardly the definition of a spring chicken, but large-scale recapping always brings with it the risk of introducing new problems as well. I would want to have an ESR meter testing at a reasonably high frequency like 100 kHz to check which ones are actually out of spec in-circuit, plus go through the schematic to identify those that haven't seen more than mere millivolts of DC in 40+ years (lower-voltage types like 16V or even 6.3 V in particular are quite likely to be toast, and may not come back to acceptable leakage current levels even with the gentlest of reforming, though it's worth a try if you have a lab power supply and multimeter good for microamps).

Electrolytics do not affect tuner alignment, their tolerances are way too great for them to be used in anything critical and they don't do well at RF. BTW, you are likely to find some orange Elnas near the stereo decoder, these are ultra low leakage types and potentially very long-lived (unless eaten by corrosive glue or unlucky enough to have had a bad seal). They never would have had super low ESR. Nichicon UKL would be a suitable replacement if needed (assuming films are not an option size-wise).

 

[yewneek]

Thanks! I've got the project slated for sometime in the next two weeks. WIll start with the filter caps and rectifier diodes.

No spring chicken but it works and performs! If it's to spec why trash a good receiver that's easy to maintain. It's far from being BPC from the 80s for the same price.

 

[restorer-john]

BTW, you are likely to find some orange Elnas near the stereo decoder, these are ultra low leakage types and potentially very long-lived

Incredible capacitors- the base is sealed with epoxy-like material.

Nippon Chemicon versions from 1976- still 100% in spec after 47 years:

@yewneek Why are you throwing a bag of parts at this receiver in the first place? Have you extensively tested the thing to determine what, if anything is not up to spec?

 

[DVDdoug]

...it can always be better. Right?

No... Once distortion and noise are below audibility, and you have flat frequency response (or the desired EQ), and enough amplifier power, etc. That's about it for the electronics.

Speakers & headphones haven't "evolved" to that point (yet?) and there will always be a difference with different speakers.

Or you can add some surround speakers (I like to use a "hall" or "theater" effect on my AVR).

Or, measure the speakers/room and do some acoustic treatment (and maybe some compensating EQ).

 

[yewneek]

I haven't given the amp a multi-tone test, I've previously realigned it as per the SM, and confirmed the power output at 1kHz clipping with a resistive load, but that was some years ago. I've done 20-20k sweeps for a cursory investigation, but nothing on the level of full testing like I did with Walkmans and tapes some years ago.

Not knowing if the electrolytics are out of spec, or not, doesn't really exclude the desire to get the thing back into what it was made, or indeed designed. I would reason the manufacturing techniques, QC, tolerances, are all improved since the late 70's.

Indeed I confirmed this with a bunch of caps that arrived from CPC today, Panasonic 100uF 25v and 220uF 16v. The 100uF were all between 100-103uF. This was confirmed with a DMM and a digital component tester. 20% declared tolerance, all within 3%. These are for a separate recap project of a phono preamp that sounds yuck. An experiment, combined with rolling opamps. You get the idea. Modern stuff is good, very good. Modern music is often rubbish tho.

Will it make it worse? Unlikely. Will it make it equal or better, this is what I'm doing it for. Will the current components last another 40 years?

Probably not, so, why not swap them out?

We now have access to the most incredible range of parts, made with the most refined processes, with tolerances and materials that are so controlled, that it would be unlikely for a mass-produced item 40 years ago to attain such theoretical levels. Would the maker, JVC, even have chosen to buy the best parts, instead of the optimal parts? I'm still buying optimal, but the parts are newer, better, known.

I'm absolutely interested in the orange Chemicons!! I'll be checking it out at first opportunity. I'll also be posting about it in this thread. How many of us do rebuilds? How many of us are interested in sharing experiences? Lots!

Audibility? We're mostly over the hill I'd wager, members of the hifi club. Can we hear beyond 12kHz? Can we erperience more than 14 bits dynamic range and discern the nuances? Blown if I could. Can I measure something to 20 bits? Actually, even with basic equipment and known properties, I'd say with a little learning and some decent empirical investigation, yes, probably. Can I do it now? Even if I could I'm not experienced enough to know what I'm looking at.


Do I still burn myself on a soldering iron? Every now and then...

 

[yewneek]

No... Once distortion and noise are below audibility, and you have flat frequency response (or the desired EQ), and enough amplifier power, etc. That's about it for the electronics.

Speakers & headphones haven't "evolved" to that point (yet?) and there will always be a difference with different speakers.

Or you can add some surround speakers (I like to use a "hall" or "theater" effect on my AVR).

Or, measure the speakers/room and do some acoustic treatment (and maybe some compensating EQ).

Yes. It's 40 years old, everything is 40 years old. 44 years old to be precise. I know I wasn't leaking half as much as I do now, back in 1979. Capacitors, I'm sure feel the same way.

Empirically, when making measurements, you need to have a zero-reference. Off-spec measurements cannot be relied upon when you've got a skewed base. Zero error simply must be eliminated.
Old components are unknown, and it's reasonable to assume the majority of electrolytics are off-spec. When replaced, the zero-error is eliminated. Empirical evidece needs a base.

 

[yewneek]

Replaced filter capacitors to Nichicon Fine Gold 10000uF/50v and upgraded rectifier diodes from 30D2 to 10A10.

Extracted caps tested to within specs even after 44 years. Glue remnants were removed with scratching and IPA.

Idle current was spot-on 5mV both channels following recap. Lead solder used.

Power board likely to be next. I may just stay away from the preamp/tuner board. Display LED's likely to be upgraded too. The current lot were pulled from cheapo Xmas tree lights!