Pioneer QX-949 CD4 red light

[maspadaro]

Hello everyone, I have taken my Pioneer QX-949 to be cleaned up but I have a question about the CD-4 red light. It's suppose to turn on whenever a CD4 LP is playing with the correct QUAD deck/Stylus... nothing to do withe the 30hz carrier level at that point. But is it attached to it? In other words it wont turn on the carrier level unless it reads that is playing a CD-4 LP correct?
The deck is playing beautifully and all functions/lights/connection are working except for that red light and I see that the carrier level is not activated..... I am aware that this deck CD-4 has always had issue and is not the best out there.

Any inputs would be appreciated

Miguel

 

[par4ken]

The CD-4 light will turn on when the unit picks up the 30 Khz carrier. The light may also (at times) blink on occasionally when a stereo record is played in the auto mode. If the light is not turning on then the demodulator is most likely not functioning.

 

[Doug G.]

Yes, the radar LED is part of the 30kHz detector circuit and so, will illuminate any time the demodulator receives a 30kHz signal strong enough for that circuit to "see" it from the turntable/cartridge. Sometimes, as par4ken said, the radar may blink or temporarily light with a regular stereo record if somehow, a 30kHz signal is output from the turntable/cartridge These are spurious signals. If it is never lighting up, either the turntable cartridge isn't outputting enough 30kHz signel for the demodulator to detect or the demodulator, itself is defective.

If the demodulator is otherwise working, presenting a discrete 4 channel output to the four speakers, I would suspect a problem just with the radar LED or it's driver. However, if there is no CD-4 performance, the demodulator, itself, is the problem if it's not the turntable/cartridge.

Doug

 

[maspadaro]

Yes, the radar LED is part of the 30kHz detector circuit and so, will illuminate any time the demodulator receives a 30kHz signal strong enough for that circuit to "see" it from the turntable/cartridge. Sometimes, as par4ken said, the radar may blink or temporarily light with a regular stereo record if somehow, a 30kHz signal is output from the turntable/cartridge These are spurious signals. If it is never lighting up, either the turntable cartridge isn't outputting enough 30kHz signel for the demodulator to detect or the demodulator, itself is defective.

If the demodulator is otherwise working, presenting a discrete 4 channel output to the four speakers, I would suspect a problem just with the radar LED or it's driver. However, if there is no CD-4 performance, the demodulator, itself, is the problem if it's not the turntable/cartridge.

Doug

TY for replying, its not the light or at least it wont matter, when I connect a CD-4 LP and connect the system and turn the Carrier level pot I get no difference in sound when I turn it Clock or Anticlockwise.
So a technical question, would turning back and forth the VR10/VR1 on the board help on this or the board needs to be fully check/ replaced? In addition I am looking at the AWX-051 Board.

 

[Doug G.]

I'm not familiar with the Pioneer receiver so I don't know what those two pots do but it's generally not a good idea to mess with the pots on the board. Have you tried adjusting the separation pots?

Doug

 

[barfle]

Hmmm. Are you getting the surround channels if the light is off? In that case, it’s probably just the light. In those days, it was probably incandescent, and may have burned out.

If you’re playing a CD-4 record, and you’re not getting the light or the back chanels active, there’s a laundry list of things it xould be, from tracking angle to cables to just worn-out records.

 

[MidiMagic]

Is your turntable CD-4 ready? It must have the low capacitance cables.

 

[par4ken]

Is your turntable CD-4 ready? It must have the low capacitance cables.

Even with high capacitance cables you should be able to get the CD-4 light to at least flash on. As far as I remember you can even get the CD-4 light to turn on using just a stereo cartridge. The demodulation would be just crashing distortion for sure, receiving a bit of carrier does not guarantee usable results. It sounds to me like his Demodulator is not functioning at all.

The Grado Superfluxbridger cartridges were said to not require special cables. Moving Coils being low impedance should also not need low capacitance cables. However CD-4 is problematical enough that I wouldn't recommend violating the rules.

I recently purchased a spare Decca Tonearm and the supplied cable measured 220 pF (82pF/ft). I would not use that cable for CD-4. I purchased some component video cables at a thrift shop the other day for a couple of dollars, they measured only 106 pF and are 6.5 feet long (16 pF/ft). I intend to cut one single cable in half (if not shorter) to replace the high capacitance ones. My point is that you don't have to spend a lot of money on fancy cables.

 

[Doug G.]

Yes, the radar lighting is just the start. Almost any good regular stereo cartridge will do that. There are really only two possibilities if the radar doesn't light, at all. Either the demodulator isn't getting a 30 Khz signal from the turntable/cartridge or the demodulator, itself, is defective.

Doug