I own a Nakamichi CR-7A. I recently bought CR-5A in order to share the wear and tear between the two (record on the cr7 and playback on the cr5). Unfortunately, the cr5's speed is a little slower than that of the cr7, enough so to get slightly different, noticeably, pitches on the two. Does anybody know of a device that could be used, without tampering with the inside of the machine, to speed one up or to slow one down? (maybe something to change the HZ on the power chord. Don't laugh; I admit my stupidity of electronics) TIA, Charles

You will have to open the deck to adjust the drive speed.
In the 60s and 70s there were some vinyl record players that used a motor synchronized to the AC frequency, but I don't know of any tape deck that does so.
Anyway, you would have to produce 230 V (or 110 V) which is quite dangerous

The motors in a tape deck are DC (direct current), not AC. A 60Hz or 50Hz AC line voltage is irrelevant for the speed of the motor.

Maybe, the problem could be the main belt in the tape deck. This belt stretches with the time and continuous use, producing a significant reduction and undesirable variations of the speed; that obvious are audible. This same problem also is present in belt drive turntables.

I would recommend you to change the main belt by a new one. This new belt must be EXACTLY the same than the original, not an imitation or replacement. You can acquire this belt in an authorized supplier Nakamichi. If this doesn't solve the problem, then, another possibility could be this: the speed from all the tape decks is calibrated by the manufacturer. This fine adjustment could also be deteriorated with time. This fine adjustment is a small potentiometer that is close to the circuit board of the motor.. but.. hey!!. Don't touch this adjustment!!!, this adjustment must be calibrated by a expert with adequate equipment, that could be also a local Nakamichi technical service. However, I doubt that this last possibility was the case. I believe that is more possible that is the main belt (as i mentioned before) which is causing the problems.

chas--
go to naks.com and join the naktalk list
also visit groups.yahoo.com and search for the nakchatt group
there you'll find the 2 best groups of classic nak deck experience and advice.
also try www.nakamichi.us which is esl labs -- the leading nak repair specialist.

your cr7 us excellent, and cr5 not far behind.

--jay

For simple decks with a single motor, you can adjust their speed with a simple screwdriver. The potentiometer for this is normally placed in the back of the motor itself, as the stabilizing electronics is sitting in the motor itself in most cases.

However, for a sophisticated drive like the Nakamichi you can screw EVERYTHING by simply changing speeds of a single motor. With some luck, there is a central potentiometer somewhere on one of the main PCBs, for exactly this.

If so, buy a master tape with a 1 KHz sine wave on it, connect a frequency counter to your outputs of both tapes and adjust them both, or one of them.

Christian