16mm Eiki motor voltage question - motor getting 240v??

[Steve Foster]

I have an Eiki NT-0 projector with the voltage selector. Serial # greater than 26135. In the 120v selector position, the motor is overheating (the windings are definitely burning, and it's a fresh motor). I measured the pins from terminal block 1 & 3 and 1 & 4 (see schematic) and read 240v. When I switch the voltage selector to 240, the motor runs fine & cool @ 120 volts, but the sound amplifier does not work. Questions — 1) Why is 240v going to the motor? 2) Can I wire to have the correct voltage going to the amp and 120v going to the motor? Can't figure it out which 120v lead to remove. I tried variations of removing one of the 120v leads at the motor and at the transformer, but motor just won't run in any of my attempts. Puzzled. Transformer stamped "NST 120 240 " and "580-115"

[Tony Bandiera Jr]

Replace the motor capacitor ("condenser") is is most likely shorted or way out of spec. It creates a phase difference in the motor and if it is bad, the windings overheat and the winding connected to the cap act like a transformer secondary and create heat.

That is, assuming the motor wiring is correct..you mentioned it is a "fresh" motor..is it an OEM motor or was it rewound recently? If rewound, it is possible that the leads were mismarked or connected wrong internally.

[Steve Foster]

The cap on the motor is new. Wondering why 240 is being sent to the motor in the first place with the selector in the 120v position?? It runs great under the 120v load.

[Tony Bandiera Jr]

Ok, but I ask again, is this the original motor or a replacement? I need to know this. Read on for why:

Now, from the schematic, it looks as though the motor is intended to run only at 240 volts, as it is connected to the 240 volt tap of the transformer. So, in 240v "mode" both the motor AND transformer primary are powered from that 240v tap.

In 120v "mode" the power transformer gets it's feed from the 120v tap on the transformer, and the motor uses that 240 tap on the transformer as its source of power (That part of the transformer acts as an "Auto transformer" Do a Google search to get the technical details as it is too complex to get into on this forum. Follow the brown wire and you'll see it. It is a very clever way to avoid having to have a dual voltage motor and it does work well.

Since the amplifier works normally when you use the 120v selection, but the motor does not, that means that the motor is not seeing the correct voltage as required by the motor.

Why? Because I am willing to bet that the motor is a 120v only type. So you have a 120v motor, that in the "correct" 120v selector mode is seeing 240v, which will make it burn. When you set the selector to the 240v position, the MOTOR is now seeing 120v and is happy, but the amplifier and other parts are now seeing only HALF of the required voltage (Feeding 120 into the 240 tap will result in only half of the design voltages on the secondary.)

If the motor is NOT OEM, but was rebuilt, there is a chance it is the correct voltage but was miswired by the motor shop. That is unlikely though since it runs ok as described above when in the "240 selector" mode.

So you have two possible solutions: One, get the right motor and change out the one you have now. IF it has an EIKI part number on it, I'll bet if you research it you'll find it is a 120v only model. If the part # says it is the right one, AND it was rewound, the motor shop screwed up.

The second solution, IF AND ONLY IF THE MOTOR IS A 120v model, AND if you have the know-how, is to remove the voltage selector switch and rewire BOTH the transformer and motor to be on the 120v tap ONLY.

Let us know what you find out about that motor.

[Steve Foster]

Thanks Tony! - You described the issue exactly. I didn't know the NT-0 series would have different voltage versions of the motor. The motor is an OEM NT motor (looks 100% identical to the original), but could very well be for a 120v-only machine. I'll take it out of the housing tomorrow and post back any part numbers I can find. Meanwhile, I'm keen on rewiring things so the motor can get 120v and the amp gets its full power. I've been deep into electronics repair, but with reel-to-reel tape decks at the transistor level, never with projector power supply issues. I will review 'auto transformer' theory in the meantime.

[Steve Foster]

It's a 120v motor!
Nidec 320-12601 stamped inside the winding cover. 50-60hz / 120v / lot 343 S16 on the blower housing label.

[Steve Foster]

So any idea how to rewire? On the voltage selector, the brown leads are on pin 6 and the black is on pin 3 per the first schematic.

[Tony Bandiera Jr]

So any idea how to rewire? On the voltage selector, the brown leads are on pin 6 and the black is on pin 3 per the first schematic.

Glad to be of assistance.

Easiest way to rewire I can see is to remove the brown wire from the 240v tap on the transformer and connect it to the black wire on the 120v tap. Leave the voltage selector in the 120v position. I would rather completely do away with the voltage selector, but since the schematic does not show the selector's internal wiring in each position, it's easier to just leave it alone. The important thing is to remove that brown wire from its source of 240v, namely that tap on the transformer. I would also make a permanent label placed on the projector's nameplate marking it as 120v ONLY.

[Mark Gulbrandsen]

I really enjoyed working on Eiki's. I used to work for a large suburban Chicago school district back in the 1970's (District 200). The district had just over 800 16mm projectors... and it's own film library to boot. About 575 of those 800 were Eiki, the rest were Kodaks Pagents. Aside from maintaining all them we had to inventory them once a year. Easiest projectors ever to work on. But the Kodak's also were not too bad.

[Steve Foster]

Sounds about right, Tony. Let me put your suggestion to the schematic, and see if this sounds right to you: 1) Cut the brown wire between pin 6 on the selector socket and the transformer. 2) Move the remaining brown wires currently on ac-terminal 1 to ac-terminal 2. Put selector plug in 120v position. Label.

(Here’s a quick description of the selector plug: the only wires on the projector’s voltage selector socket are the ones described — the brown leads are soldered to pin 6 and the black is soldered on pin 3. If the selector plug is in the 120v position, then the mains (black) connects with the brown transformer wire. If the plug is in the 240 position, then the mains connect to the black transformer wire.)

[Steve Foster]

Yes Mark — very simple to maintain and repair; rock solid. Now if I can just fix this stupid motor issue...

[Tony Bandiera Jr]

Sounds about right, Tony. Let me put your suggestion to the schematic, and see if this sounds right to you: 1) Cut the brown wire between pin 6 on the selector socket and the transformer. 2) Move the remaining brown wires currently on ac-terminal 1 to ac-terminal 2. Put selector plug in 120v position. Label.

That will work. I saw that the transformer has a 9 pin connector involved that would also make isolating the brown wire easy. Just cut the brown wire (pin 1) off right at the transformer side of the connector and securely tape a wirenut to the end of that transformer lead. (Best to also completely remove that pin 1 on the connector so it won't have a live wire stub sticking out. Otherwise cut far enough away from the connector to wirenut and tape that end too.)

As for the fuse, if it is part of the selector as the schematic implies, be aware that your method would bypass it. To prevent that, do step one on the lead at the transformer connector as I just suggested above. But, and this is important, for step two you MUST tie the brown lead from the motor to pin 3 on the selector socket. (Or splice the brown wire to the black from pin 3) If you simply move the browns to terminal 2 on the AC board you have bypassed the fuse.

if it is in a separate holder wired ahead of the selector socket, your method should work, but verify that the fuse is still in line with the incoming black wire from the power inlet/cord, and before terminal 2 on the ac board!

(Here’s a quick description of the selector plug: the only wires on the projector’s voltage selector socket are the ones described — the brown leads are soldered to pin 6 and the black is soldered on pin 3. If the selector plug is in the 120v position, then the mains (black) connects with the brown transformer wire. If the plug is in the 240 position, then the mains connect to the black transformer wire.)

Nope, that is backwards. Look at the transformer part and notice that the black is on the center tap of the primary, that is the 120v tap, brown is on the end and that is the 240v full primary tap. The way they word it is confusing and not clear since there are different types of selectors evidently.

Good luck..

[Steve Foster]

Looks good - I'll do the revision tomorrow and report back. And you are right — I got my selector description reversed (It says 240v right over the 120v pin & I let it influence me).

This will have me remove the 240v brown-wire from pin 1 on the transformer's male 9-pin connector), insulate it, and move the remaining brown wire from voltage selector socket pin 6 onto the 120v black selector socket pin 3 so that black & brown then occupy that pin. Properly fused. Thanks for your help and for sticking with me — you clarified my understanding of the circuit with every response.

[Steve Foster]

Works perfectly now - thanks again for your help in sorting this out, Tony.