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Type: Posts; User: Hugo Holden

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  1. Thank you. It is interesting that they are out...

    Thank you.

    It is interesting that they are out of stock of the fabric reinforced version of the belt, so they might have been a popular spare part, but they still have the rubber one.
  2. Commodore 1541 5.25" disk drive question.

    I bought a 5.25" Commodore 1541 disk drive unit. I want to use it in conjunction with my AIM-65 computer. I have also bought an AH5050 board and ROM to make it work (hopefully) when I get them.
    ...
  3. I find a good supplier for these sorts of things...

    I find a good supplier for these sorts of things is Digikey and only 74 cents each:

    https://www.digikey.com.au/product-detail/en/bourns-inc/4610X-101-472LF/4610X-1-472LF-ND/1089205
  4. It is almost certain that this capacitor is...

    It is almost certain that this capacitor is directly on a power supply line, with little else in series with it, or there would have not been enough current to cook it up.

    But sometimes there...
  5. Yes M is likely the tolerance.

    Yes M is likely the tolerance.
  6. Yes, it likely is in a supply bypass application,...

    Yes, it likely is in a supply bypass application, so you could use a 3.3uF 25V Tant or a 4.7uF if you wanted. The usual rule is don't go below the original rated voltage.

    For their uF size &...
  7. The black capacitor which shows a damaged casing...

    The black capacitor which shows a damaged casing (as Dwight predicted) is a 3.3uF 25V rated Tantalum type.

    The end with the taper and the + making is its positive terminal.

    It became customary...
  8. I agree with Dwight. With the voltages...

    I agree with Dwight.

    With the voltages available to the drive, it would be pretty difficult to overheat most resistor arrays of over a few hundred ohms. If you see a cracked resistor array, that...
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    I'm a bit confused because you said it was the...

    I'm a bit confused because you said it was the same under load in a previous post, but now the +5 and +12 go down under load ?

    Can you describe the load you put on the +5V and +12V outputs, was it...
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    There could be a clue there. It suggests you are...

    There could be a clue there. It suggests you are testing the supply with no load on it ? that is the only way it could take so long for the caps to discharge.

    Since the supply works on a feeback...
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    Hugo.

    Hugo.
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    ...If it turned out to be the heater supply from...

    ...If it turned out to be the heater supply from the LOPT causing the banding, I don't think adding an inductor could help as that will just tend to average the current, reducing the rms value and it...
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    Maybe if we could find the data sheet for the...

    Maybe if we could find the data sheet for the CRT, or had a true rms reading meter, we could work out the heater voltage, or a digital scope with an rms readout of the wave.

    If you could post a...
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    ....... what I suggested above is plausible....

    ....... what I suggested above is plausible. Looking at the schematic again, the phase of the ripple that would be in the 178V source, when its not well filtered, is opposite to that presented to the...
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    That is difficult to understand how increasing...

    That is difficult to understand how increasing the filtering on the supply rail results in increasing the banding (or fluctuations in CRT beam current). That might suggest that the signal causing the...
  16. For the most part, in most video monitors this...

    For the most part, in most video monitors this is, the DC axis of the video signal is not that important, because right at the monitor input, the connector is terminated with a 75R resistor (Unless...
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    Yes, the white glass diodes that are mounted onto...

    Yes, the white glass diodes that are mounted onto the three metal heat sink flags. But likely they are ok, because they are probably for the + power supply that is working, but they are easily...
  18. Well I guess they took some liberties and the...

    Well I guess they took some liberties and the composite signal is deviated away from what would be true NTSC standard, that a color TV or composite video monitor was "expecting" to see at its video...
  19. The sync tip is fine siting above zero volts, you...

    The sync tip is fine siting above zero volts, you could increase the pull up resistor value you have added so the level is closer to zero volts, but still just above it.

    It is very hard to tell on...
  20. "The old-type CGA card doesn't have the base...

    "The old-type CGA card doesn't have the base pullup resistor".

    That is not good at all.

    To get the resistor ideal : Put a scope on the video output, with the scope set on DC input. Put a...
  21. I wouldn't start unsoldering IC's yet, there has...

    I wouldn't start unsoldering IC's yet, there has to be a good reason found on testing to suggest one needed replacement, otherwise it risks damage and introducing other faults.

    The way to do it is...
  22. The big question is , is it definitely ok using...

    The big question is , is it definitely ok using the CGA output connector to a CGA monitor, but not on the composite output ?.. if so it cannot be anything to do with the image software or the card's...
  23. That V sync is normal, you are just seeing the...

    That V sync is normal, you are just seeing the leading edge of an H pulse just before the vertical pulse starts. Since the H and V pulses are mixed in an XOR gate, one has the effect of inverting the...
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    Yes I agree, looks like the B version. But still...

    Yes I agree, looks like the B version. But still worth checking all the diodes on the secondary side, and it would be D9 & D10 that need checking, but these look physically ok on the photos.
  25. Interesting that the Chroma also appears to drop...

    Interesting that the Chroma also appears to drop out and unlock, just prior to the H sync being disturbed. One quick test to eliminate an oddity in the chroma signal channel would be to disconnect...
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