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  1. kellys_eye

    Computer PSU Repair

    Check the devices bolted to the aluminium heatsinks - those that are located between the two heatsinks and not shown clearly in your pictures. It is probably the main rectifier for the 12V secondary side and is commonly a dual schotkky diode (in a single 3-pin package).
  2. kellys_eye

    Complete beginner help with finishing linear DC supply

    That constructional layout seems perfectly acceptable to me and would even work in a 'finished' device when suitably boxed/housed. If a PSU is derived from a mains AC source, as many SMPS devices also are, then the dangers are no different in terms of voltage and current. If it was down to...
  3. kellys_eye

    Rotel RA820A stereo amp no right channel

    Theoretically, with no signal input, the voltage at the fuses is 'zero' so if you are measuring -37V you have a shorted output transistor to the -ve supply line (Q622). That device needs testing/replacing but there's also the possibility that a transistor driving that device has shorted...
  4. kellys_eye

    Complete beginner help with finishing linear DC supply

    Those parameters give some indication of the power rating of the transformer (VA) and equates to 360 watts but the 3A rating is usually overstated so I'd give that transformer a potential 250VA rating. On the secondary side, after losses, this might deliver 200-ish VA to a power supply such as...
  5. kellys_eye

    Complete beginner help with finishing linear DC supply

    That's about right but getting 52V seems rather high - it is, of course, not under any load but the capacitors are rated at only 56V and that seems too close for comfort. Adding a load shouldn't see a drop from 52V to the expected 36V(ish) so something seems amiss. Make sure you measure from...
  6. kellys_eye

    Complete beginner help with finishing linear DC supply

    Show how you connected the secondary of the transformer to the rectifiers/capacitors. The 40-0-40 secondary would be the red-black-red wires. Note that the shortest wire between the two capacitors are likely unconnected and simply there to offer mechanical support to the soldering process...
  7. kellys_eye

    Complete beginner help with finishing linear DC supply

    Can you show us how you did this? The centre tapped transformer could deliver a dual-rail PSU solution which is often required for hi-fi pre-amp and output stage voltages. The difficulty is that you have a rather high DC level which makes the final design more complicated than it needs to be...
  8. kellys_eye

    i am Dean Smuth

    Q. If God is omnipotent can He make a rock so big He can't lift it?
  9. kellys_eye

    NASA MARINE ST50 TRIDATA

    You say the fault occurs on certain days so, presumably not permanently. When you tested it on a different display (PCB) and it worked then maybe it was a day there wasn't an intermittent fault. Check the cable back from the display to see if there are any junctions or joints in the cable...
  10. kellys_eye

    Vacuum tube tesla coil HELP

    What value are the three blue capacitors in series across the 50W resistor? You do know that the values don't 'add up' when they are wired in series? Other than that I'm not happy telling people how to kill themselves. That MOT looks dangerous a f*** I'l assume that if we don't hear back...
  11. kellys_eye

    NASA MARINE ST50 TRIDATA

    The SENDER is the device fitted to the hull of your vessel, nothing to do with the display or PCB. It could be something as simple as a fish lying under the vessel or even seaweed. Sure you know the basic principles of how these things work?
  12. kellys_eye

    NASA MARINE ST50 TRIDATA

    First, how do you know? What is your reference for the ACTUAL depth? and on that/those particular days? How great is the error? Secondly, is the error a constant or variable? If it's not erroneous digits (i.e. LCD segment error) then either get another sender and place it in a fixed, known...
  13. kellys_eye

    Rotel RA820A stereo amp no right channel

    There's no risk. The damage has been done. This isn't CMOS stuff so the risk of other faults happening are minimal.
  14. kellys_eye

    Rotel RA820A stereo amp no right channel

    Check the +37 and -37V rails then measure at either end of F601 and F602, report all you find.
  15. kellys_eye

    Rotel RA820A stereo amp no right channel

    That's not the track, that's just the topside print to assist with following the circuit layout - the tracks are under the board.
  16. kellys_eye

    Rotel RA820A stereo amp no right channel

    Too late! Usual issues, apart from capacitor ESR, would be a short in one of the amplifier output transistors but we must establish that the sections are receiving the right voltages and that there's no bad ripple (as a dud capacitor would introduce). Sure you didn't inadvertently cross the...
  17. kellys_eye

    Rotel RA820A stereo amp no right channel

    Did you use the correct rated fuse? 4A is not exactly common and replacing it with something larger is a no-no. What are F901 and F902 like? I'd check for distorted smoothing capacitors first (visual checks first) then we can start doing some basic test measurements assuming you have a test...
  18. kellys_eye

    Simple, or so I thought. Creating circuit to transform 24vac control to 12vdc.

    Bwahahahah! The only time you have real security is when you aren't wired into the net. Not that I'm mocking your application - some good work, kudos. But please don't use the word 'Alexa' in the same sentence as 'security'.
  19. kellys_eye

    Control 240v Electric Heater with ESP8266

    Why use a standard relay? Have you not considered an SSR or opto-isolated triac? In this way you can at least offer PID control rather than the simple bang-bang of a relay contact? It would also 'stretch' your programming abilities in a good way!
  20. kellys_eye

    PROMAX AE-566

    Wattage 'adds up' regardless of series or parallel wiring. That test board needs to be made up (or purchased) accordingly and will load up the relevant PSU outputs at which point you will measure the fixed DC values (or waveforms) according to the tests they specify. The resistance totals...
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