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  1. KrisBlueNZ

    Which voltage transformer for a laser printer

    I read John Sirutis's review. It sounds OK. If possible, buy it from Amazon in your country. They should be responsible for validating its safety and type approval. Your prices seem to show that the 3000 VA model is cheaper than the 2000 VA model. If that's true, then go for the 3000 VA model...
  2. KrisBlueNZ

    NAD T752 Repair - need 5.1V 2W zeners

    "PSU" stands for power supply unit. I think you're asking whether the transformer is OK or not. From those voltages, I don't see any problem. The negative side of C707 will measure about -21V DC relative to 0V. That's right. It doesn't mean there's a "short somewhere". Re D701~704, I suggest...
  3. KrisBlueNZ

    NAD T752 Repair - need 5.1V 2W zeners

    Those voltages on pins 9~14 look OK. Pins 9, 10, 13, and 14 should measure about 17~18VAC relative to the 0V rail of the circuit (the chassis). Pins 11 and 12 should measure 0V relative to the 0V rail because they're connected to it. To check the voltages on the other pins: 1. Measure AC...
  4. KrisBlueNZ

    Tank reverb

    Please don't start a duplicate thread on the same subject. You can post a new message on the existing thread. You can start with the basics, by telling us the brand and model number of your amplifier and your tank reverb unit. You can also Google those keywords along with "service manual" or...
  5. KrisBlueNZ

    Basic concepts PCB building and dsPIC

    Hello and welcome to Electronics Point :) A PCB manufacturer will send you a bare PCB. You can send it to another company to get the components installed, but that's only economical for large-quantity runs. So you'll need to source and install the components yourself. Yes, your board will need...
  6. KrisBlueNZ

    Next/previous switching a multiplexer

    Pullup and pulldown resistors are needed when a device (e.g. a transistor or a pushbutton) only pulls the signal in one direction, to ensure that the signal assumes the opposite state when that device is not active. In your circuit in post #11, R17, R19, R2, R4, R6, R8, and R11 are all pullup...
  7. KrisBlueNZ

    Create Memory/RAM

    Hello Raul and welcome to Electronics Point :) You're a beginner? Why not start with something simpler. Perhaps a spacecraft, or an MRI machine! :) Yes, you can make RAM from transistors... a LOT of them! I guess you're using the traditional "single bit static RAM" - a bistable multivibrator...
  8. KrisBlueNZ

    Next/previous switching a multiplexer

    Yes, and I don't find those arguments very convincing, except perhaps during development with SMT components. For one-off designs that are built up on stripboard (which I guess this is), it's easy enough to disconnect pins that have been tied to VDD or VSS if that is ever required. To the OP: I...
  9. KrisBlueNZ

    Next/previous switching a multiplexer

    Harald, does that mean you use a separate resistor for each unused input?
  10. KrisBlueNZ

    Which voltage transformer for a laser printer

    Sure, ask any questions here. I don't have much experience with 230VAC-to-115VAC transformers, but others on this site do.
  11. KrisBlueNZ

    Designing a Time Delayed Relay

    I don't know about how 220VAC is obtained in countries with 110VAC systems, but it doesn't matter; all that matters is that there's 220VAC between two wires. These wires can be connected through to the 220VAC motor to make it run. You break one of the wires in that path and insert that...
  12. KrisBlueNZ

    NAD T752 Repair - need 5.1V 2W zeners

    You should also check out this thread on the Usenet archive: www.electronicspoint.com/threads/very-hot-hot-zenerdiode-in-nad-t762.100781
  13. KrisBlueNZ

    NAD T752 Repair - need 5.1V 2W zeners

    OK, thanks for the info. Those zener diodes are just there to drop a bit of voltage to help regulators U702 and U703. Here's the relevant part of the schematic: If D716 has overheated, this could be due to a fault downstream - perhaps U702, or perhaps something that's powered from U702 -...
  14. KrisBlueNZ

    NAD T752 Repair - need 5.1V 2W zeners

    Zener diodes in different power ratings have different characteristics. Can you tell me the circuit references (e.g. ZD303, ZD304 or something like that) for the two you want to replace, so I can see where they are in the circuit? Then I should be able to tell you whether you can use a 5W zener...
  15. KrisBlueNZ

    Help needed for 12V lead-acid switched mode battery charger.

    Adam: OhMy wants to make a battery charger powered from 200~240VAC that can supply a fixed 14.4V DC at up to 30A with smooth current limiting. He is operating on a budget. We've suggested that he starts with a PC power supply and modifies it, but he says he can't get one. He wants to build one...
  16. KrisBlueNZ

    How to take photos of circuit boards

    If you ask for help with a faulty circuit board, contributors will often ask you for photos. This is important early in the thread, so we all know what we're dealing with. In almost all cases, photos will help. We may also see something in the photo that points to a specific fault. Here are...
  17. KrisBlueNZ

    Broken Cans (headphones)

    Thanks shrtrnd :-) I'll suggest it to the other moderators. There's no specific forum for MIDI equipment. Just start a new thread in this forum, Electronics Repair. Include the brand and model number, and photographs of the relevant parts of the insides, if you dismantle it. Also, please...
  18. KrisBlueNZ

    Help needed for 12V lead-acid switched mode battery charger.

    OK, I really can't comment authoritatively because I have very little experience with forward converters - my experience has been with flyback converters. Do you need external diodes across the drive MOSFETs? Or are the internal ones adequate? Are you planning to use 0.6 mm diameter wire for...
  19. KrisBlueNZ

    M2732A can not erase or program

    Also, different brands can have different requirements - VPP voltage, timing. That's why I asked for all the markings. Manufacturer, date code, full part number.
  20. KrisBlueNZ

    Next/previous switching a multiplexer

    Regarding non-volatility. There is no simple way to add it - at least, not that I can think of. It's so obviously the kind of thing that a microcontroller would do that I don't even like to think of how to add it to a "dumb" design. I think the answer would be to have the 40193 powered from a...
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