Marantz CD-400B problem

[rxc]

Hi there. I am a newbie to this group, and I hope that someone can give me some ideas. I have a Dual 1249 turntable and a Marantz CD-400B demodulator, but am having problems with the Marantz. The turntable is putting out a good signal, but it is not getting thru the phono-preamp section of the CD-400B. The light on the front of the unit comes on as normal, but nothing comes out of the 4-channel output. When I look at the direct 2-channel output, I see the direct signal from the turntable. Having read a few posts on this group about recapping projects, I suspect that maybe the CD-400B needs to be restored. Has anyone else seen anything like this?

Thanks in advance for any insights.

Ralph Caruso

 

[mtgc]

Welcome to the wonderful world of quadraphonic sound reproduction. You will find in this Forum a group of knowledgeable people on almost any facet of 4 channel sound reproduction.
A few questions about your setup. How long have you had this setup? What are you using as an amplifier for the CD-400B? If the radar light comes on, usually that indicates that at least the decoder portion of the CD-400B is working properly, and if you get a signal when you set the CD unit to direct, then at least portions of the wiring within the CD unit are good. Have you tried putting signals into the aux inputs to see if you get any output from the CD unit? Also, although I am not sure, I suspect that the CD unit has a relay that operates to supply 4 channel outputs, so you might check that relay and see if it is operating properly, and also give it a dose of De-Oxit contact cleaner.

I am sure that some of our Marantz guru's will step in with much better advice than mine, but at least here is a place to get started.

Good luck and again, welcome to the wonderful world of quadraphonic sound reproduction.

MTGC
Michael

 

[rxc]

Thanks for the quick reply. I am the original owner of both the turntable and the 400B, having bought it back in the 70s. I also had a 4-channel Heathkit that I built to play all the quad records that I bought. Unfortunately, the Heathkit died, probably due to leaking capacitors (it had two ENORMOUS electrolytic caps in the power supply that leaked, and I could not find any replacements for them). So, now I have a very large record collection that I want to transfer to my computer, and am trying to get enough hardware working to make the transfer. I am not worried about getting the quad sound transferred - just stereo would be fine for me. Unfortunately, the 400B was the front end phono-preamp, and it is not working. I hear a relay click when I turn it on, and have opened it up to look for obvious problems - the fuses are fine, and no signs of leaking caps.

My wife is losing patience with this project, and if I can't get the 400B working, I will just buy a stand-alone preamp, but I thought I would see if anyone else has seen this problem, and maybe there is a quick fix. But I am not really ready to do a complete cap replacement project.

Once again, thanks for your help.

Ralph Caruso

 

[mtgc]

Ralph,

Find the relay that is clicking and give it a shot of contact cleaner. Sometimes you will have to remove the relay cover to get to the contacts and do this carefully as you can cause contact alignment problems if you are not careful.

Out of curiosity, what Heathkit did you have? I still own an AR2020 which is the center of my den system. I don't use the Heathkit decoder since it was non-steering non-logic, but the amp itself and associated tuners are absolutely fantastic.

Good luck on your project.

MTGC
Michael

 

[rxc]

Michael,

I believe that it was an AR2020, and I may even still have the manual somewhere. It was a great unit. Thanks for the hint - I will give it a shot tommorrow AM.

Ralph

 

[rxc]

Well, after some more thought, I realized that I had connected the computer into the "2 CH Direct Out" connections, and once I changed to the "4 CH Out" jacks, all works well. Turns out the 400B still works, and I didn't have to clean any contacts, and I don't need a new phono-preamp. I did clean all the other possible contacts/jacks, and had to tweak the separation controls to get an output that sounded good without distortion, but now the project to capture a whole bunch of vinyl is on track.

Thanks much for your help.

Ralph

 

[mtgc]

Glad it worked out for you. Good luck on the transfers.

MTGC
Michael

 

[aelfric]

This topic looks fresh enough and I do have a problem with the CD-400B demodulator as well, so maybe one of the more experienced collegues will be able to help.

To put it simple, the left channel doesnt seem to work at all. The 4 CH logo lights up, and the radar does light up when fed a CD-4 signal from the turntable. The right channel plays front/rear, the left does not. The right channel plays with no matter which signal, the left one doesn’t.

I checked that the TT signal and it works fine over both channels when used with another phono preamp. It also works on both channels when plugged into to the Marantz and returned through direct outputs.

I looked inside and the fuses are fine, inside the Marantz looks extremely clean, it’s hard to believe it’s well over 30 years old. No sign of parts burnt, leaking, etc.

Is there anything simple I can try myself? Second question, the available diagrams for the CD-400 (not 400B) – will they be helpful for the repair shop (...if I find any willing to deal with something that esoteric)?

The set up is Bang and Olufsen 2400 turntable with the MMC 20CL cartridge + JVC 4Vn-880 integrated amp

Thanks in advance

Michal