Loddestuen
New Member
Hello everyone,
Anyone here with JVC CD-4 circuit experience?
I've gotten a quad amp from a friend - Its a JVC 4VR-5456X - and once cleaned up, it it in beautiful condition. I have cleaned out all the pots and contacts with Kontakt 60 -> Kontakt WL -> Kontakt 61 by the book and everything seem to work properly. All but the phono stage - it was completly dead in one channel :-(
After taking a look inside i saw A LOT of Hitachi 2SC458 with nasty black legs..
After changing about 40 of them on the CD-4/phono board, the tone control and one on each output amp board i was looking forward to listening in low noise music.. (I put in Fairchild KSA1845 as i usually do with Akai RtR and tapedecks)
The problem at hand after B-52'ing it with new transistors:
All inputs and tuner works so tone control and output amps is doing great, but the phono stage sound awfull. Both channels are now living again, but you can barely hear who's on the record. It sounds very distorted with only treble/high notes.
It sounds very much like in the very end of this video from VWestlife when he listens to the CD-4 sub carrier at 30KHz (5min 10sec):
I have the service manual, but there is nothing in here about measuring/checking and adjusting the CD-4 board.. Only FM/AM tuner alignment. (I could also use some guidance in setting the amp bias - as this is not mentioned either..)
I should have all the measuring equipment needed on my bench for this job..
Please help me ;-(
Kind Regards from Denmark
Jesper
Anyone here with JVC CD-4 circuit experience?
I've gotten a quad amp from a friend - Its a JVC 4VR-5456X - and once cleaned up, it it in beautiful condition. I have cleaned out all the pots and contacts with Kontakt 60 -> Kontakt WL -> Kontakt 61 by the book and everything seem to work properly. All but the phono stage - it was completly dead in one channel :-(
After taking a look inside i saw A LOT of Hitachi 2SC458 with nasty black legs..
After changing about 40 of them on the CD-4/phono board, the tone control and one on each output amp board i was looking forward to listening in low noise music.. (I put in Fairchild KSA1845 as i usually do with Akai RtR and tapedecks)
The problem at hand after B-52'ing it with new transistors:
All inputs and tuner works so tone control and output amps is doing great, but the phono stage sound awfull. Both channels are now living again, but you can barely hear who's on the record. It sounds very distorted with only treble/high notes.
It sounds very much like in the very end of this video from VWestlife when he listens to the CD-4 sub carrier at 30KHz (5min 10sec):
I have the service manual, but there is nothing in here about measuring/checking and adjusting the CD-4 board.. Only FM/AM tuner alignment. (I could also use some guidance in setting the amp bias - as this is not mentioned either..)
I should have all the measuring equipment needed on my bench for this job..
Please help me ;-(
Kind Regards from Denmark
Jesper