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Type: Posts; User: Hugo Holden

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  1. Replies
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    After some research in this area I would use a...

    After some research in this area I would use a product called Inox MX-3 because there are no issues with induced corrosion on metals containing copper & zinc (or any others) and it leaves a very very...
  2. Also, I just love the naming of computers and...

    Also, I just love the naming of computers and electronic components from the 1970's era.

    For example "Intertec Superbrain" very cool. And many other examples, companies like Signetics and...
  3. Wow, very impressed. I very much admire your...

    Wow, very impressed. I very much admire your never give up attitude. I'm am like that when it comes to repairs.
  4. That suggests to me that the designer, back in...

    That suggests to me that the designer, back in the 1970's, probably had a long history of designing in RTL and DTL and applied the idea to TTL.
  5. Looking at it, they paralleled two of the '05...

    Looking at it, they paralleled two of the '05 gates to make sure that the output got forced low, which actually would have been easier with a 74LS75 than the 7475 because the LS series have a higher...
  6. Interesting (unusual) Logic Technique.

    I'm in the process of building a replica of the Cromemco Dazzler. So I have been studying the circuitry to understand how it works and prepare myself for any technical issues that might eventuate.
    ...
  7. I would suggest, order the exact three small...

    I would suggest, order the exact three small transistors and the chopper transistor. Fit them at the same time (you have checked the diodes).And order a few extras.

    Load the 5V supply output with...
  8. One very interesting thing is to look at the way...

    One very interesting thing is to look at the way a 110/220V switched option SMPS was implemented in the 5155 computer.

    It also answers an interesting question, which could perhaps be posed in an...
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    I would like to experiment with this board. So...

    I would like to experiment with this board.

    So far I have experimented with the ALT 256 and ALT512 Boards and written articles on them, both of which I had to write my own software for.

    I...
  10. I agree, it can be done in steps so that the...

    I agree, it can be done in steps so that the ultimate spacing of the pins on each side of the IC matches the spacing of the socket entry points.

    The pushing down part you mentioned is very...
  11. Generally , wired in the 230V mode, the input...

    Generally , wired in the 230V mode, the input rectifier and filter system is wired as a full wave bridge rectifier (4 diodes) to charge the capacitor pair, but in 115V mode, it's wired (or switched...
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    Welcome. Apart from vintage computers, I got...

    Welcome.

    Apart from vintage computers, I got turned on to Japanese motorcycles when I saw the movie, in the 1970's, with Charlton Heston called the Omega Man, A post apocalyptic world where he had...
  13. The three associated transistors on the primary...

    The three associated transistors on the primary side are very important, two, acting as a latch limit the chopper's base current and the other the emitter current, so if they are not working the...
  14. The most likely reason why this would happen...

    The most likely reason why this would happen would be either the current rose too high through the chopper transistor, melting it's junction, or that it's collector voltage got exceeded. Previously I...
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    I'll give an explanation of retrace lines. In...

    I'll give an explanation of retrace lines.

    In the composite video signal, on either side of the sync pulses, the level of the video voltage is defined as "black level" .The meaning of this is that...
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    Generally non polarised caps are used in video...

    Generally non polarised caps are used in video monitors, not often because in use they are exposed to both DC polarities but because they require a low ESR. AS noted you will find them in...
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    The is RF interference or noise in the modulated...

    The is RF interference or noise in the modulated RF carrier or the RF carrier is very weak. Possibly the TV could be tuned to the wrong sideband, try altering the fine tuning controls. Check for any...
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    In my experience they tend to fail, when they do,...

    In my experience they tend to fail, when they do, shortly after power up.

    Though many years ago I was sleeping in a room that had a Singer electric sewing machine in it. It was switched on, but...
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    I wouldn't be too worried about those. The...

    I wouldn't be too worried about those.

    The great thing about the line power supply voltage, is that it has a very low internal resistance and it can supply the 110V to a 1kW bar heater.

    So if...
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    Impossible to make an educated guess of the video...

    Impossible to make an educated guess of the video issue without a photo of it.
  21. yes that would work.

    yes that would work.
  22. Replies
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    Possibly this contact re-directs the magnetic...

    Possibly this contact re-directs the magnetic field in a way that minimizes the interference with the CRT beam. If you can find a way to do this, whatever it is, then that may be the solution.
  23. Looking at the schematic, it is fairly...

    Looking at the schematic, it is fairly straightforward.

    A separate secondary feedback winding phased for positive feedback generates the supply to turn on the chopper transistor. This supply from...
  24. Normally to kill the bridge rectifier, something...

    Normally to kill the bridge rectifier, something else fails, for example the main filter cap fails or the chopper transistor shorts out, taking the bridge out with it, if any fusing doesn't save it...
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    Yes we agree. I think that thin type of copper...

    Yes we agree. I think that thin type of copper foil is intended as an electrostatic shield product, not an electromagnetic flux band application. So its a matter of folding/forming one up from some...
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