MUTR-kit circuit diagram

[Klaas Robers]

Yesterday the MUTR-kit was delivered in Valkenswaard. Now I could measure and find the remaining parts in order to backwards engineer the electronics of the board. Some wirening is hidden below the motor and that makes life less easy.
The diagrams are copied more or less from the website of the NBTVA, however that is already mentioned in an add on sheet that comes with the kit.
This diagram is of the Version 3 Revision 3 board. A change in respect of V3R2 is the addition of C6.

[Ralph]

The diagram is very helpful Klaas as I am awaiting my own MUTR kit. I intend to customize/modify it in the end, so it is always useful to know where the various bits should have been!

Ralph

[Klaas Robers]

Ralph, it worked immediately after assembling. However there are a few things:

1. The kit uses a red LED. That gives less light than an orange-yellow LED because our eyes are less sensitive for red. I think that I am going to change it.

2. The diffuser is far too transparent. The center of the picture is much brighter than the edges. I will look for a better diffuser.

3. The picture synchronises good, but with the sync bar exactly in the middle of the viewing window. I don't know yet how to change that. The framing can be shifted with the speed control, but then the synchronisation is less stable and tends to speed up the disc to too high speeds.

4. The CD that comes with the kit doesn't run in a CD-player. It is written in a weird CD-ROM data format, in stead of wave files. So it is not an audio CD. Also the sync stops each phragment and resumes each next phragment. It took me an afternoon of processing and recording a new CD-R to make an audio CD with uninterrupted sync.

[Ralph]

Klaas,

Your comments are quite helpful, especially in light of other postings with respect to the kit:

1. "The kit uses a red LED. That gives less light than an orange-yellow LED because our eyes are less sensitive for red. I think that I am going to change it."

I can see that optimum use of some alternative LEDs might require some modification of the LED modulator and operating voltage.

2. "The diffuser is far too transparent. The center of the picture is much brighter than the edges. I will look for a better diffuser."

The "workload" of the diffuser is increased by the use of a single LED against the relatively dark background of the LED circuit board. I think one could surround the single LED with a small reflector array that would result in more uniform illumination of the image field, perhaps making the choice of the diffuser material less critical. Of course a small array of even four LEDs would also help, but that puts us back to #1 and some mods to the LED driver.

3. "The picture synchronises good, but with the sync bar exactly in the middle of the viewing window. I don't know yet how to change that. The framing can be shifted with the speed control, but then the synchronisation is less stable and tends to speed up the disc to too high speeds."

If the sync bar is horizontal (a line sync phase error), a slight lateral shift in the position of the optical sensor should eliminate the problem.

In any case, if I didn't enjoy tinkering, I would buy a television set and not a televisor!

Cheers,

Ralph

[Klaas Robers]

Ralph, I will look for the problems to solve. One solution for the LEDs is to make a new LED-board that has a connection to an extra battery to increase the voltage (LEDs in series). It is now already marginal.

The optical sensor is in a fixed position, clever designed, but unhandy in this case. I have to see wether I can rotate the stroboscopic disc in respect to the Nipkow disc without ruining them.

[Ralph]

Klaas,

Would it be practical to make a xerographic copy of the strobe disc that could be applied over the current disc once the optimum position had been determined?

Ralph

[Lawnboy]

Klaas, would this 6v motor control circuit work well with the club's sync separator PCB, or would it need to be upgraded to 12v?

[Klaas Robers]

Oh Ralph, that is a good idea. I am going to do that. But first I have to decide what the optimal position is.

Lawnboy, I think that the motor control circuit will work as well at 12 volt. Most important is to find out at which voltage the motor runs the correct speed. I just found out that the MUTR-motor runs the correct speed at 2,2 volts, which is rather low for a moror. It is not bad if the motor runs the correct speed at about half the supply voltage. So if your motor runs 12½ rev/sec at 6 volt then your supply voltage should be 12 volt.

In any case the supply voltage of the sync separator board and the motor control board should be (almost) the same. The sync pulses that go into the 4046 circuit should have the same amplitude as the supply voltage of the 4046. Yes you can do something with resistors to lower the amplitude of the sync pulses of course. But first run your disc motor, place a stroboscopic disc on the spindle and run it on a variable voltage to find the voltage at which it runs the optimal speed.

[Ralph]

I think you can estimate the new position with some precision based on the location of the sync bar. If it is centered, then mounting the new strobe disc offset (either direction) by 1/2 of a cycle on the strobe pattern would probably do it.

Alternatively, you can spot mount the new disc pattern (rubber cement, etc.) at different offsets. Once it is behaving, cement it permanently into place.

Ralph

[standard8films21]

A new member here - Very happy to see a circuit diagram for the MUTR televisor !

I have been playing around with my MUTR televisor for a month or so. Results as follows :

- Replacing diffuser greatly improved picture quality, but did not eliminate the "hot spot" in the middle of the picture. This was fixed by adding some additional pillars to mount the LED further away from the diffuser. The additional distance allows the bright disk projected by the LED to become bigger than the overall image size.

- I have also found that the picture is most stable with the sync bar right in the middle of the viewing hole. This seems to be supply voltage and "warmup" sensitive. With fresh batteries after 15 minutes of running, I can get a stable picture in the middle of the viewing hole, but this drifts off as the supply drops. Worse with nicad batteries, because they are only 1.2v to start with. A bench power dupply running a touch over 6v fixes this problem.

- Sticking some bits of cardboard to the diffuser will mask off the extra images above and below the primary image.

Regards

Nick
Bristol
England

[AncientBrit]

Welcome to the forum Nick.

re diffusers I think it was Klaas who suggested using a pair of diffusers in tandem with a space between was better than a double thickness with no gap.

Not sure whether milk "bottle" container material would be of use.
It's not too dense.

Elsewhere others have suggested semi-opaque "Scotch" tape.

Regards,


Graham

[Panrock]

I have also found that the picture is most stable with the sync bar right in the middle of the viewing hole.

I carefully stripped off the paper sync wheel and re-positioned it half a line round to try to get rid of this effect.

To remove the 'hot spot' I used a drafting-film diffuser and a wider angle, white LED.

Steve O

[Klaas Robers]

Oh Steve, is that a way that leads to success? Is the sync wheel just self adhesive and can it be removed? That would be nice.

I think that I will firstly scan the sync wheel into my computer. Then, if the peeling goes wrong, I can make myself a new one on the printer.

I also measured the voltage at the gate of the IRF 530. When the disc is synchronised the voltage is 1,9 volts. The voltage at the drain was 3,7 volts (= 5,9 - 2,2 mentioned earlier).

White Line.....
The front of the MUTR-kit comes with two lines engrave. I hadn't removed the protective foil yet. Today I filled the engraving with white paint and then after some drying I removed the foil. This gives a nice line around the edge and a line around the sticker in the centre. The MUTR webside told about a guy that filled the engravings with white filler wax. ??? I haven't that stuff....
I know Denis had too white lines painted on this Televisor replicae. He knew a Belgian guy that did this by hand for him..... His replicae had the same shade of brown. Looks good.

I didn't like to run the kit always from batteries. So I mounted two bushes for 2mm banana plugs in the rear panel. The batterybox got these, as well as a 6V DC-adapter that I saved long ago. Now the Televisor can run on this adapter as well. For a quick show the batteries are still available.

[Lawnboy]

can someone tell me what kind of capacitors the motor circuit uses, and the pinout for that transistor? i am trying to make a layout so i can build it separately for my system.

[Klaas Robers]

The 100nF capacitors are foil capacitors, the 22uF is an electrolytic capacitor and a max. voltage of 10V or more.

The pin-out of the IRF530 is, when the type number is readable (pins down):
Gate (to C4, R18 and R19), Drain (to motor), Source (to 0V).

Yesterday I did some interesting experiments with the MUTR kit. Firstly I soldered a 22 ohm resistor parallel to the motor. In fact it could replace the diode D7, but the diode does no harm. Then with the oscilloscope to the long leads of the resistor I observed the voltage accross the motor. Now I could see that sometimes the motor synchronises correct, sometimes it is one line leading, sometimes one line trailing. Until now I didn't find a setting in which the motor synchronises always correct.

The correctness of frame sync can be observed at the TEST CARD. When correctly synchronised there is one white line left and on right of the characters of "CARD". When not one is missing and you see too one inverted line left or right of the "checkerboard".

Switching off and on might change the synchronisation, but when wsitching off too short the microprocessor may be "hanging" and no video or rubbish video is generated. So switch off long enough to assure a proper reset of the uC.