Improving the sound quality coming from a Nikko ND-390 II, anyone got a schematic?

[freax]

I've got myself here a Nikko ND-390 II and I've just soldered in a Nichicon MUSE 1000uF capacitor as the old one was looking a bit aged.

The belts have been replaced with brand new ones, so the hard part is already done.


Got a schematic someone could scan so I can improve the high end performance of this unit from 1985?

Are these heads heavily worn? What about the capstan rubber freewheel?

I put some copper tape on the back for shielding and I'm about to add my own special taste, a couple of BNC sockets, to the back, you might notice that I've insulated the mains wiring with a strip of duct tape, just to be doubly sure, especially if I'm going to be modifying this unit or improving its peformance.

Here are some more shots of its innards:

View from the trap door:

Notice the bnew Nichicon MUSE at the bottom right, this is where power comes in.

[freax]

Direct line output from the opamps:

[freax]

Will have to clean the pinch roller vigorously tomorrow, otherwise this excellent deck is a total loss as on record and playback its got quite a bit of wow and flutter.

No matter I've got several other decks to choose from, might setup the Pioneer tomorrow and maybe a Marantz later on.

[Mooly]

The W/F could be a backtension problem. Something like a sticky surface on the hub the backtension band runs on (assuming it has one)

[freax]

Originally Posted by Mooly

The W/F could be a backtension problem. Something like a sticky surface on the hub the backtension band runs on (assuming it has one)

I fixed the problem.

I checked the flywheel hub and it was spotless, so was the motor shaft, I also hit the rubber pinch roller with some 1200 grit wetted wet and dry.

I think the problem with the wow and flutter was being caused by the tape counter, the cheap plastic cogs in the tape counter had after all of these years turned into dried out unlubricated rough edged mushy plastic.

I'm not sure if it was either one of those but I'm betting that it was the tape counter.

This tape of Billy Joel live at Yankee Stadium in 1990 plays perfectly on the Nikko now aswell as a portable Sony Walkman WM-FX171 with zero symptoms of wow or flutter.

However both the Sherwood DD-1032C that I own and the Pioneer CT-W103 show huge symptoms of wow and flutter...

I don't think I'll bother repairing the cheap and nasty looking sherwood or pioneer.

It would be good if I could get ahold of an EG510ED-2B 12v DC motor, would be able to replace the probably tired old motor then, I'll have to go hunting for one.

[freax]

apparently the EG530AD2B is a good substitute for it:
Tapeheads.Net - View Single Post - Nakamichi Motor

Another option is an EG530KD-2B. It a two speed motor. All you do is buy a small 5K trim pot and connect it to the two extra terminals and you are good. May stores have them in stock. Here in US it's Audio Lab of Georgia.

Once installed, you adjust the trimpot for correct speed using a speed tape and counter.

EG500AD2B = EG-530AD-2B MABUCHI SPINDLE MOTOR | eBay

[Mooly]

It could well have been something like the tape counter, particularly if there is old dried grease around there.

Motors tend to be pretty universal in mounting and fall under single or twin speed CW or CCW rotation. There might be a speed pot behind that sticker on your motor. Some ancient motors (often in car audio) used a mechanical governor where the commutator windings were routed through contacts on sprung weights. As the motor speed increased centrifugal force opens the contacts and the speed stabilises. These motors often had huge torque.

Yours is most likely a 12 volt CW 2400 rpm type with an electronic regulator on board. As a spares item they seem to have dropped off the radar nowadays, used to be able to get universal motors very cheaply.

[freax]

I suspect my wow and flutter issue is inside of the motor, did it again tonight.

I bet that motor hasn't been lubed in 30 years.

Everything else seems to be in pefect condition.

I'll take it apart tomorrow and lubricate it with some motor oil.

If I can save the motor then I'll save $10.