Can't get CD-4 to work

[ress4278]

Hi,
This is my second question. I am stumped. I hooked my JVC 4-DD5 demod back up after hearing about all the exciting listening experiences people talked about. For years all I have listened to is SQ thru a S&IC. When I turn on the 4DD-5 all I am getting is a loud hum. The Dual 1229Q that I have is 2nd hand and may not have the correct cables installed. Is it necessary first to make sure that the cables out from the TT are the correct ones?
Thanks a million. Lance

 

[quadanasaziland]

Hi Lance!

This hobby can be a bear! If the 1229Q was playing your SQ stuff ok then your cables are probably ok. I don't know if we have enuff info here, I am assuming that you are using the Dual as your main table and that you now have it connected to the JVC demod. Dual TT's are hard wired with standard rca's. I had a 510 that I used for cd-4 and when ever I connected it some times I would have to rotate (twist) the wires at the rca's where connected to the demod to end that type of feedback or hum (old wires). Try doing that with all power off to every thing. Check the cart wires to be sure they are not loose, I use sugical foreceps. If there is a ground wire on the 1229Q make sure you have it properly connected. Get back to us with more info on your setup.

 

[ress4278]

Hi Lance!

This hobby can be a bear! If the 1229Q was playing your SQ stuff ok then your cables are probably ok. I don't know if we have enuff info here, I am assuming that you are using the Dual as your main table and that you now have it connected to the JVC demod. Dual TT's are hard wired with standard rca's. I had a 510 that I used for cd-4 and when ever I connected it some times I would have to rotate (twist) the wires at the rca's where connected to the demod to end that type of feedback or hum (old wires). Try doing that with all power off to every thing. Check the cart wires to be sure they are not loose, I use sugical foreceps. If there is a ground wire on the 1229Q make sure you have it properly connected. Get back to us with more info on your setup.

Hi Dave,
Thanks for getting back to me. Here's the setup: Dual 1229Q, AT 440 ML cartridge, (5-32000 Hz ) (I'm not sure if this will suffice for the carrier signal), 2 Amber amps, S&IC, JVC 4DD-5,
4 Fried Q5 speakers, assorted "above average" speaker cable and interconnects, Threshold preamp, KLH TNE 7000, (tick and noise eliminator). Let me know if that gives you enuf to go on.

 

[quadanasaziland]

Hi Dave,
Thanks for getting back to me. Here's the setup: Dual 1229Q, AT 440 ML cartridge, (5-32000 Hz ) (I'm not sure if this will suffice for the carrier signal), 2 Amber amps, S&IC, JVC 4DD-5,
4 Fried Q5 speakers, assorted "above average" speaker cable and interconnects, Threshold preamp, KLH TNE 7000, (tick and noise eliminator). Let me know if that gives you enuf to go on.

32k will light the carrier but above that I don't know, maybe some one more familiar with the 440 can chime in. The rest of the system is great so it seems that the JVC may be the problem. Open it up and see if there is any thing obvious if not then they go cheap enuff on ebay to spring for another one. The techs here still arn't restoring demods (other than CD-4 boards in the 7001/9001 that QB does). Bob will try a Panasonic 405 for me down the road, when I get around to sending him one.

 

[ress4278]

32k will light the carrier but above that I don't know, maybe some one more familiar with the 440 can chime in. The rest of the system is great so it seems that the JVC may be the problem. Open it up and see if there is any thing obvious if not then they go cheap enuff on ebay to spring for another one. The techs here still arn't restoring demods (other than CD-4 boards in the 7001/9001 that QB does). Bob will try a Panasonic 405 for me down the road, when I get around to sending him one.

Davwe,
I did a litlle testing: is this revealing in any way?
All volume controls down, 4DD-5 going thru the S&iC
1) 2 CH diract switch in he back of the demod in the off position, & the front selector switch in 4-CH. THERE'S A LOUD HUM.
2) Same except the front selector is 2 CH. DITTO
3) Front and back selector in 2 CH NO HUM.
4) FRONT 4 CH, back 2 CH THERE'S A LOUD HUM.
If this suggests anything, please let me know.

 

[sspsandy]

Davwe,
I did a litlle testing: is this revealing in any way?
All volume controls down, 4DD-5 going thru the S&iC
1) 2 CH diract switch in he back of the demod in the off position, & the front selector switch in 4-CH. THERE'S A LOUD HUM.
2) Same except the front selector is 2 CH. DITTO
3) Front and back selector in 2 CH NO HUM.
4) FRONT 4 CH, back 2 CH THERE'S A LOUD HUM.
If this suggests anything, please let me know.

The 2/4 channel selector switch in the back of the 4DD5 is notorious for causing this hum. Spraying it with some tuner spray and working it may clear it up. Also, I do not run the 4 output cables into the Tate, I run them into the 4 channel aux input on the receiver, run the Tate into the 4 channel tape monitor. :sun

 

[ress4278]

The 2/4 channel selector switch in the back of the 4DD5 is notorious for causing this hum. Spraying it with some tuner spray and working it may clear it up. Also, I do not run the 4 output cables into the Tate, I run them into the 4 channel aux input on the receiver, run the Tate into the 4 channel tape monitor. :sun

Thanks Sandy. I'll clean the switch and see what happens. The Tate is the only outlet I have for discrete playback. Does anyone else use their S&IC for CD-4 plyback?
Lance

 

[The Quadfather]

You can use the discrete inputs on the S&IC to connect a CD-4 demodulator. It works fine. I have also wyed the front channels to feed the matrix (SQ) inputs, so that the demod can be used as a phono preamp. It sounds like a bad filter capacitor in the demod, or the turntable ground is not connected to the demod. That demod is nearly 30 years old. It will need some capacitors replaced, if not all of them. I have two 4DD5 demods and I had to replace caps and a transistor, but once repairs were made, it is a very stable and reliable demodulator. It is not a bad idea to replace every capacitor, but it isn't necessary. Just make sure you get the bad ones. There will be several, more than likely. Good Luck!

The Quadfather

Thanks Sandy. I'll clean the switch and see what happens. The Tate is the only outlet I have for discrete playback. Does anyone else use their S&IC for CD-4 plyback?
Lance