Separate CD-4 demodulator

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gvl_guy

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I bought a new old stock JVC about a year ago. When I received it in the mail, it would not turn on. I gave it to a local stereo store to repair it. They recapped it and said it needed a few new relays. It really hasn't been right, I'm not getting great CD4 out of it. I used the one in my receiver now. So just be careful, New Old stock might not be the way to go. The shop told me you really need a unit that has been powered on a few times and it's lifetime.
 

fredblue

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I bought a new old stock JVC about a year ago. When I received it in the mail, it would not turn on. I gave it to a local stereo store to repair it. They recapped it and said it needed a few new relays. It really hasn't been right, I'm not getting great CD4 out of it. I used the one in my receiver now. So just be careful, New Old stock might not be the way to go. The shop told me you really need a unit that has been powered on a few times and it's lifetime.
totally! this ol' stuff likes to be used! i noticed the "Blend" switch on the back of my Grundig demodulator has started leaking since i relegated it to the closet.. eek šŸ˜¬

also, gotta say i'm surprised to hear the Sansui outboard CD-4 unit is not just a 4DD-5 clone like almost all the others! šŸ¤Æ
 

Doug G.

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Years ago, now, I got both a Panasonic SE-405 and a Technics SH-400 and (I know I'm tempting fate) they have been perfect.
You should get the seller to guarantee the unit works and if he won't, don't buy it unless the seller will agree to pay for return shipping if it doesn't.

Demodulators are complex devices and it's difficult to correct problems in them beyond simple power supply cap. replacement. A CD-4 expert is needed and they are very rare, these days.

Doug
 

MyCuff

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Well ,I'm travelling to Oregon this summer. The QRX restore shop is only like 30 minutes away from Corvallis. Too bad I can't take the QRX as a carry-on. Anybody ever send one with them as luggage? Seems like it would more dangerous than shipping.

The CD-4 demod seller specifically says he is unable to test, which I believe. No way will he guarantee it.
 

Doug G.

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There is no way I would leave a piece of equipment in the hands of airline baggage handlers.

If the seller cannot guarantee function, he should agree to paying for return shipment if it doesn't work and you want to return it. There is no way you should be out any money, at all, if it's defective.

I have talked sellers into paying return for a defective product even when they state "buyer pays return shipping". Ethically, there is just no way the buyer should be out any money if something doesn't work, unless the seller specifically says the item is defective. Then, as a buyer, you take your own chance.

Doug
 

gvl_guy

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Is it the demodulator in your receiver that's bad? The QRX Restore was really nice working with me and my Sansui, walking this non-techie guy through some things and, if needed, I could have just sent the demodulator board to them. Unfortunately, I blew out something else after I opened it up and had to send the entire unit back. (Turned out to be a fuse. :rolleyes:) But they fixed the demodulator (replacing some resistors) and I'm back in Quadradisc action!
 

MyCuff

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Actually, As I recall, I sent them the demodulator board. Was it separate from the phono board? If so, I pulled out and sent both boards back in 2016-2107 time frame, and both boards tested good. They also did the full restore in 2015. I have faith in their work, but I think it's not the actual board but some sort of connection issue. I don't relish the idea of shipping the entire unit across country and back again. I greatly prefer the sound of the music hall phono preamp over the integrated phono preamp, for both stereo and quad, but that may be because there is just something not quite right about the phono section in general. If using the onboard phono, the right side is always weaker, and the VU meters objectively confirm what I subjectively hear. The demodulator does work. I can play CD-4 LPs and get 4 discrete channels, and I feel like I dialed it in correctly using the Sansui CD-4 test record. It just does not sound that good.
 

jupp369

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I bought a new old stock JVC about a year ago. When I received it in the mail, it would not turn on. I gave it to a local stereo store to repair it. They recapped it and said it needed a few new relays. It really hasn't been right, I'm not getting great CD4 out of it. I used the one in my receiver now. So just be careful, New Old stock might not be the way to go. The shop told me you really need a unit that has been powered on a few times and it's lifetime.
The JVC 54x6 have only 1 Relay for the speakers: it get's dirty, has to be cleaned with fine sandpaper. And it get's weak, need a slight adjust. Changing is nearly impossible.
But all the capacitors from 50uF up needs to be changed except the both big power (>6800uF), without any problems, easy to reach. The are leaking, see the brown sauce at their bottoms. ... and change the lamps to LED.
Than you got a good working amplifier, like new!

You can also add a new In / Out just behind the RIAA for recording and playback CD4 from DVD. Works good and saves your vinyl.
 

gvl_guy

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The JVC 54x6 have only 1 Relay for the speakers: it get's dirty, has to be cleaned with fine sandpaper. And it get's weak, need a slight adjust. Changing is nearly impossible.
But all the capacitors from 50uF up needs to be changed except the both big power (>6800uF), without any problems, easy to reach. The are leaking, see the brown sauce at their bottoms. ... and change the lamps to LED.
Than you got a good working amplifier, like new!

You can also add a new In / Out just behind the RIAA for recording and playback CD4 from DVD. Works good and saves your vinyl.
Actually, it was the JVC 4DD-5, so speakers shouldn't be any issue.
 
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