CD4 demodulator - left channels wont separate!!
OK to paint the scene:
I have a CD4 etc set up using a JVC 5436 as a switching unit for my quad stuff connected to a Sony DA5000 ES (170WPC x7) Receiver and Monitor audio radius 270 speakers.
I use a Tascam 234 as a 4 ch. mixing unit ( good VU meters - calibrated) with all 4 channels going though some Marantz equalisers first.
Somewhere in there I also have a Sony SQ decoder (2030) which I run a Nakamichi cassette player and an Akai GX635D Reel to reel player through and a JVC 4DD 5, spare cd4 demodulator. Finally a an Akai Quad 8 track and a denon 2910 which is fed directly to the Sony Amp. So most bases covered...
My Linn record deck has a Denon DL110 and that works well with the 5436 receivers inbuilt demodulator and the JVC 4DD5 demod giving about 20-25db of separation.
I am now trying to change to a JVC JA X9 Quad /CD4 amp as it has more 4 ch inputs than the 5436. Again I’ll just use it as a switching unit.
I would like to use the built in CD4 demodulator but am having difficulties...
I am setting up the separation using the VU meters on the Tascam but the left channels seem to be operating in unison even when the left separation control is adjusted. I have seen this before during the set up procedures for the others but no amount of adjustments to the carrier tone or L/R sep levels alters it in this unit.
If I make changes to the pots on the CD4 board (JVC TDM-13E) for the right channel then I can optimise the separation and unwanted noise levels of the right channels but changing them for the left channels has no effect at all?? I assume therefore that the left signal is not running through the board or the carrier tone is not recognising the left channel??
Further, if I switch mode from CD4 to stereo whilst running the channel separation tests and then come back to the correct input (CD4) then the left channels 'separate' for about 3 seconds then slowly revert to an equal level. Ie the rear channel loses it's separation from the front.
I assumed that this would indicate a duff component and tried using freezer spray on the caps etc with no luck. A transistor failure would be on or off - I think?? Maybe not??
Running my meter over the board I cannot find any unmatched values between the two channels and have checked as best I can for a short circuit.
Finally the CD4 light only comes on for a few seconds and then disappears and I confirm that the right channel shows good separation and responds to all pots on the Demod board.
I do hope that some of you may find this interesting and could make suggestions.
I have a full set of schematics if that helps and have already changed a suspect cap but to no avail.
Chris
OK to paint the scene:
I have a CD4 etc set up using a JVC 5436 as a switching unit for my quad stuff connected to a Sony DA5000 ES (170WPC x7) Receiver and Monitor audio radius 270 speakers.
I use a Tascam 234 as a 4 ch. mixing unit ( good VU meters - calibrated) with all 4 channels going though some Marantz equalisers first.
Somewhere in there I also have a Sony SQ decoder (2030) which I run a Nakamichi cassette player and an Akai GX635D Reel to reel player through and a JVC 4DD 5, spare cd4 demodulator. Finally a an Akai Quad 8 track and a denon 2910 which is fed directly to the Sony Amp. So most bases covered...
My Linn record deck has a Denon DL110 and that works well with the 5436 receivers inbuilt demodulator and the JVC 4DD5 demod giving about 20-25db of separation.
I am now trying to change to a JVC JA X9 Quad /CD4 amp as it has more 4 ch inputs than the 5436. Again I’ll just use it as a switching unit.
I would like to use the built in CD4 demodulator but am having difficulties...
I am setting up the separation using the VU meters on the Tascam but the left channels seem to be operating in unison even when the left separation control is adjusted. I have seen this before during the set up procedures for the others but no amount of adjustments to the carrier tone or L/R sep levels alters it in this unit.
If I make changes to the pots on the CD4 board (JVC TDM-13E) for the right channel then I can optimise the separation and unwanted noise levels of the right channels but changing them for the left channels has no effect at all?? I assume therefore that the left signal is not running through the board or the carrier tone is not recognising the left channel??
Further, if I switch mode from CD4 to stereo whilst running the channel separation tests and then come back to the correct input (CD4) then the left channels 'separate' for about 3 seconds then slowly revert to an equal level. Ie the rear channel loses it's separation from the front.
I assumed that this would indicate a duff component and tried using freezer spray on the caps etc with no luck. A transistor failure would be on or off - I think?? Maybe not??
Running my meter over the board I cannot find any unmatched values between the two channels and have checked as best I can for a short circuit.
Finally the CD4 light only comes on for a few seconds and then disappears and I confirm that the right channel shows good separation and responds to all pots on the Demod board.
I do hope that some of you may find this interesting and could make suggestions.
I have a full set of schematics if that helps and have already changed a suspect cap but to no avail.
Chris
