Nakamichi CR-4 Only Recording on One Channel...need help!
I bought a used Nakamichi CR-4 from eBay and it turns out that it only records on the Left channel and not on the Right channel.
When I use the manual calibration function present on this deck, it calibrates the Level to 0db but only goes upto -20db when Bias is calibrated using TDK SA cassette even after turning the Bias knob clockwise to the max. I have also tried calibrating using an EX tape with the correct tape type and equilizer setting but still cannot calibrate the Bias to 0db.
I have aligned the playback head using test tapes but when I try to align the recording head height and azimuth using 400Hz and 15KHz test tones, it only outputs to the Left channel and I only get a very small voltage on the Right channel as compared with the left channel.
Also, when recording the 15KHz test tone the voltmeter displays 15KHz on the left channel but it barely registers 1KHz (and that is also fluctuating between 500Hz and 1KHz) on the right channel.
I did go ahead and aligned the recording head based only on the output readings of the Left channel in the hope that it may bring the Right channel somewhat back into alignment if it was very mis-aligned, but to no avail.
Any thoughts on what could be wrong with the deck, any suggestions on how to fix it? Any help will be geratly appreciated.
Re: Nakamichi CR-4 Only Recording on One Channel...need...
I AM AN AUDIO CASSETTE DUPLICATOR TECH,AND LAST WEEK AFTER USING MY IN CASSETTE DUPLICATOR TASCAM 2640,I FIGURED THAT I LOST ALMOST 95% OF ONE CHANNEL AFTER CLEANING WITH THE TASCAM HEAD CLEANER IT REMAINS THE SAME,SO I DECIDED TO USE CLEAN ACETON,AND I WAS SURPRIZED THAT THE DEAD CHANNEL CAME BACK LIKE A HERO WITH NO PROBLEM.
AMAZING WHAT A BIT OF ACETON CAN DO.
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Re: Nakamichi CR-4 Only Recording on One Channel...need...
Hmmm.....heres a really stupid question but........is the head clean ? There may be a bit of oxide shorting the one side of the head out. Try cleaning the head with a q-tip and some 99% pure isopropyl alcohol. If you have done that ( you seem to be more knowledgeable than most ), I would suspect either the circuit that drives the right channel record head, or the head itself. Is the head running flat against the tape?. Is there a record/play relay or record relay somewhere in the circuit ?. I think at this point you really need a schematic. Do you have the AC oscillator signal ( bias ) present on the right record head ?. I would try this first, then look into a manual.......Good luck...Rob
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If it plays back a pre-recorded tape OK, then the tape head will be good. If it doesn't you might have problem, with either the head or the pre-amp stage.
However if it is playing back OK but not recording, then you have problem in the record circuit. Some tape decks physically switch the circuit when you press record. Pushing the record button will cause a switch to move position. In some cases dirt or dust can get into the switch and it doesn't connect properly. Switch cleaning fluid will correct the problem.
However the record circuit itself could be faulty. Perhaps an IC has developed a fault on one channel, which will need to be replaced.
Watching what happens when you press record with the top cover off, showing the workings, might point to some movement of the mechanism to reveal a faulty switch.
It is strange that people go to belts when that has nothing to do with the problem at hand. The probably cause can be a defective record enable switch or there have been some Nak decks that have a defective capacitor in the Bias oscillator circuit. The only way to find out is to do the troubleshooting that is necessary. It may need belts but that does not stop a unit from recording. The deck is playing so the problem is with the Bias oscillator turning on. I bet it does not erase either.
This is down to the head alignment. Once that is corrected the sound will recorded normally and playback normally too. However any tapes recorded during the fault will not play right.
The head alignment can be corrected, using two adjusting screws located either side of the head. To get at them the door cover has to be removed. To align you play a pre-recorded good quality tape. You adjust the screws till the sound is bright and clear and only the sound recorded on that side of the tape can be heard. Best done with headphones. If you can use a commercial music tape. If you use the decks own recordings it might not be right.
If there is any damage to the head mounting you will not be able to get the alignment right.
PS use the right screwdriver for the head screws. These are very small and easily wear away. If you wear the screw head away you might have a job getting a new small screw that will fit.
It has a transport that needs attention. This is work for a Technician and they are still around but you need to find a good one. Nak units are best worked on by people that used to service them for the company. Tom in Nashville at HI Tech Service is one of those people.
If he had it done by a person who knows what he is doing he most likely used a 1/2 track tape recording device. These are different than 1/4 track unit as they are used professionally an for mastering. You would need to find a 1/2 track type deck to play the tape back- they are made by Tascam, Otari, Studer, Pioneer, Sony and other lesser brands.
This sounds like an recording pre-amp problem. Anything common to both channels problem faults are always connected with a device that has both channels going in and out of it. In this case I suspect a recording pre-amp IC.
It's a 4-channel recorder. That's four recorded channels in the same direction. You COULD use it like a standard 2-channel stereo recorder with bi-directional playback if you recorded only the front tracks. THAT would produce a 1/4-track stereo tape with two sides (directions).
In the photo, the front and back are clearly marked.
Oxide deposits on heads can restrict audio transfer to tape. You may need to do a deep cleaning of record head. Depending on how much deposits are on heads may need no more than alchohol and Q-tip. Be sure to clean erase head and drive roller. Afterwards, try recording, then use headphones in jack on recorder to check for recording on both channels. If this works, problem is not in rest of equipment set up. If you still need help, email me