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RCA VCR MODEL VMT-400 Problem

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    RCA VCR MODEL VMT-400 Problem

    Hi all this is a shot in the dark...but VCR loads...but no other functions. The main capstan motor which controls most functions does not activate. Motor checks out good. Maybe someone has circuit board location , and common cap problems. Its been a long time without use...Thanks Al

    #2
    Re: RCA VCR MODEL VMT-400 Problem

    The first thing to check is the belts, the loading belt could be bad an not loading completely. Provide some pictures of the mechanism. This vcr is over 30 years old
    Last edited by R_J; 03-25-2020, 10:41 AM.

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      #3
      Re: RCA VCR MODEL VMT-400 Problem

      Thanks for reply RJ.....All belts are good. Capstan motor on top of large pulley, controls almost everything (play, ff, rew) It is not engaging after tape rollers pull the tape to head..therefore rollers pull back to position and unit goes to STOP.
      Two pics enclosed...Thanks Al
      Attached Files

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        #4
        Re: RCA VCR MODEL VMT-400 Problem

        Make sure the loading motor is loading the tape all the way, Those two small belts on the loading motor could be slipping and not loading fully. If the tape does'nt load all the way, it will time out and unload.
        If you grab the belt and pull it away from the pulleys, it should snap back. Those belts usually get like gum and when stretched, slowly shrink back.
        Does the video drum start up when the tape is loading?
        Also check the voltages coming from the power supply, they should be marked on the board near the plug.
        It could also be that the mode switch needs cleaning, these switches were usually ok but after sitting this long the contacts could be tarnished.
        Those pictures are too small (400x300)
        Last edited by R_J; 03-25-2020, 08:32 PM.

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          #5
          Re: RCA VCR MODEL VMT-400 Problem

          The video drum does not rotate. The loading motor is the only motor working...The tape up rollers go all the way up ( belts are good) When rewind and ff is pressed the clutch moves to proper spindle but does not turn ( since the capstan motor is not functioning) I traced the wires coming to the capstan motor from the circuit board...I was hoping to find some bulging caps ....but all look good. Thanks Al

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            #6
            Re: RCA VCR MODEL VMT-400 Problem

            Is the tape end sensor lamp, lit? These older vcr's used a small incandescent lamp.

            The drum should start spinning as soon as play is pressed and the tape starts to load, if the drum does'nt spin, the capstan motor won't be started either.

            One more thing to check is the tape end sensor lamp, if this lamp is open I believe it can cause this.

            Check that all the fuses are ok on the power supply, You could be missing (If I remember) 9 or 12 volts. If I recall there is a stxxx ic on the power supply that outputs a couple different voltages.
            Attached Files
            Last edited by R_J; 03-27-2020, 07:28 PM.

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              #7
              Re: RCA VCR MODEL VMT-400 Problem

              The lamp is infrared...impossible to tell if lit. But if the lamp was burnt out I don't think the tape up rollers would pull the tape to the head. The 3 power line fuses all check good. I traced harness from video head motor to circuit board, and no bulging caps. Do you believe the capstan motor would not function if the video head don't turn? It is very difficult to check voltages from power supply, without pulling half the set apart. Where would I find the mode switch? Thanks Al

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                #8
                Re: RCA VCR MODEL VMT-400 Problem

                The power supply should lift out, there may be one or two screws holding it in place. I guess I was thinking of an older model that used the lamp for the end sensor, this must be new enough to have the IR emitter.
                The drum starts before the tape is loaded, because if you wrap the tape around the drum before it starts, it likely won't start due to the tape wraped around it, or if it does start it will grap the tape an pull it from the cassette.
                The only time the capstan motor starts is in Play, FF or REW. or when stop is pressed and the tape is being wound back into the cassette
                As for the mode switch, I can't tell from the small picture, it is on the bottom, near the loading motor
                Attached Files
                Last edited by R_J; 03-28-2020, 02:37 PM.

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                  #9
                  Re: RCA VCR MODEL VMT-400 Problem

                  Yes, you were correct. The P/S came out with 2 screws. I measured AC going in (120v) and out of transformer are 9 pins. They all show DC current measuring from 28v-10v. So it seems the DC is going out. Unlike schematic, there are no voltages noted on circuit board. Thanks AL

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                    #10
                    Re: RCA VCR MODEL VMT-400 Problem

                    I checked voltage to capstan motor...and none is present. Harness to drum motor has 12 pins...getting 10.6 v on 3 of them nothing on others. Mode switch is working properly. Do you think anyone might have schematic? If not, it might be time to say good-bye. In any event thanks TJ for all your help and stay safe!
                    AL

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                      #11
                      Re: RCA VCR MODEL VMT-400 Problem

                      With just the tape loaded, rewind and fast forward should work without the drum spinning.
                      The capstan motor circuit should not be too complicated, The drum uses a 3phase motor with phase generator for speed control.
                      As for a service manual, I doubt you will find a pdf of it, someone might be selling a paper version. I would have had the service manual at one time but it is now likely a paper plate or toilet paper.
                      The closest service manual I could find would be for a hitachi vt33e It might help.
                      Last edited by R_J; 03-31-2020, 04:16 PM.

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                        #12
                        Re: RCA VCR MODEL VMT-400 Problem

                        On the Hitachi model, the capstan motor drive ic is on the power supply module. The RCA model might be similar. Like I said, without good pictures, it is hard to help.
                        Last edited by R_J; 03-31-2020, 08:22 PM.

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