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Posts posted by electrodoc

  1. [glow=red,2,300]***__-- TUBE BASE VOLTAGES CAN AND WILL!! BITE--__***[/glow]

    I'm not familiar with this model but providing the chip that you refer to isn't fastened to a heatsink then this procedure is a failsafe way of finding where the fault is. It can be used on any transistor driven gun array and i always employ this method.

    First check the drive circuit on the tube base, there will be a plug going from the tube base to the main board where the IC001 lives. three of these leads should be traceable to the red,green and blue drive transistor base connections. disconnect / cut the wires for the red and blue and swap them over. Then if your screen still lacks red there is a fault on the tube panel or possibly the tube itself, if your screen lacks blue then the fault lies within the RGB driver chip on the main board.

    Reconnect your swapped leads and then check the tube by following the track from the 'BLUE' drive transistor to the relevant pin on the tube base socket and desolder the pin, do this with the 'RED' pin also. Then with a thin piece of insulated wire soldered to the 'BLUE' tube base boards socket pad* (see picture) touch the other end of the wire to the tube sockets 'RED' pin.

  2. The filter is working very well now since changing C1, C2 and C3's values to those you specified ,thanx guru.

    However the frequency response is very dependant on the setting of RV1 and the intensity of the audio signal, with OR without the 3.3nf cap.

    The unit will be used in a very loud room and music volumes will be lower in some parts of the room and higher in others. So this problem is an issue which would need resolving.

    Changing the microphone type or adding desctrete extra stages isn't a problem for me, one i was toying with is the addition of the filter circuit here.


  3. When using a transistor as a buffer/inverter I find a simple way of remembering the rules for these jobs are as follows..

    To remember the transistor type when looking at schemetics
    I use Point iN Please and Not Point iN, these are for the emitter arrow directions and the voltage polaritys for them to work.

    For the polaritys i use the emitter as my reference and proceed by using each junctions P or N initial as the (P)ositive or (N)egative supply they need to get to switch through between Emitter and Collector.

    therefore a PNP to switch needs a positive current or feed to the emitter and a negative (Lower current) feed on the base for the collector to be positive.

    Hope this helps.

  4. Hopefully this new theory thread will help in my own and other users quest's to understand How these filters are worked out..

    A few questions to sart the ball rolling would be...

    1)..I can see that R2 + the volume control (RV2) sets the gain for the primary amplifier but what about R3 and R6, is R3 for stability and are R6 and R7 needed?

    2)..How do I work out the gain that I want and then work out the resistances required?

    3)..Is the gain affected by any bandpass filters and vice versa?


  5. ??? Thanks audio guru. I used a 22nf + a 2.2nf for the 18nf and the 3.3nf respectively ( numbers on caps where 223 (22nf) and 222 (2.2nf). If these capacitor code translations are wrong then please mention it.

    shurely these values should be ok? but it wouldnt play ball.

    The 2.2nf was tried between the current limited power output of R8 and T1 collector. also tried between the wiper of RV1 and T1's collector and between the wiper upto R8'S output. But to no avail.

    It would flash to the beat of the music but also flash to any other noise (ie talking in the room).

    Please help.

    thanks,, Rich

  6. I've decided to call RL2 a "latency control relay". this is because it LOOKS like it does nothing, but it was found that when the motor went into reverse there was a 10th of a second or so when the motor would go forward and then into reverse while the coil of RL1 would be pulling the contacts together when the motor was reversed. So RL2 was added for the properties of the time it takes for the contacts to close when power is added to the coil. Therefore as power from RL1's contacts are applied to the coil of RL2, both relays contacts are mode at the same time so power is applied to the motor at the point that RL1 has made its mind up which way to turn the motor, eliminating this latency problem.

    RL3. This was added to the door design to allow a change in speed as the door got to the mid open/closed point, this speed change is latched by a magnet riding in the centre of the door that closes the reed switch momentarily latching RL3 and putting the 10 ohm 7 watt resistor in series with the motor.

  7. I'm Building a 8X8 LED graphics display at the moment ran on the same principle so more posts on this to come.

    If any one knows how to scan a character and return a value that i can output to the port then that would be most handy

    to make it clearer i know how to do the opposite ie for the letter L, it would be 1,1,1,1,1,1,1,255. but i need to input that letter then have some code which will scan it and then return that binary result.. Idea's please??? preferably qbasic code if poss.

    Cheers Rich :-*

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