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DrV

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    Dave Vallance

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  1. That's exactly right. You only need 100V to get the full nominal output. Any amp which is capable of driving 20 or 30 volts will give you enough level to identify speakers. In fact using the minimum required to be just audible will probably help overcome the problem of distinguishing multiple speakers in earshot that Brian mentioned.
  2. With high volume manufacturers like Behringer, pots are often slightly custom versions of standard parts from the likes of ALPS. If you buy half a million pots you can have any combination of value, spindle length, spindle style, orientation etc. you want. Can you post a picture of it? It might be a standard one.
  3. From my years of bodging motorbikes when I was a teen... I see you've already got the Plusgas out and copious amounts of that and a lot of patience will help but another aid might be to tap it all the way around with a hammer and drift or chisel held tangentially to the ring. Tap it in the unscrewing direction of course. You have a good surface to tap against with all the knurly bits.
  4. Silly me - yes, could easily be inductors. More likely in fact.
  5. 220 in that size of case almost certainly means 22nF but if that's the only marking then you'd also need to specify a suitable voltage and dielectric type. The working voltage needs to be at least the same as the supply rail voltage but ideally around twice that. So if your supply is 40-60V you'd fit a 100V part. Dielectric type would be polyester film. With a cursory search I can't see any cylindrical, radial leaded ones like that but there are plenty of axial lead or rectangular box types available. Edit: are you sure the caps have failed and that the black goop isn't just the adhesive holding them down? It does seem a different colour from the rest though.
  6. The driver circuits on the main PCB are constant current drivers so you won't be drawing any more current from the PSU. You could get a VERY rough measurement of the total power being consumed by just measuring the mains current if you have something to measure that safely. It won't be at all accurate but if you can compare the current drawn by an original unit and a modified one you should find it's a little less. It's just a reassurance measurement to set your mind at ease!
  7. Reducing the output voltage of the PSU won't increase the current at either the input or the output per se. However, the total power required by the old plates was 140W and the new ones require 180W. Therefore the current drawn by the original plates was 5A (140/28) whereas the new ones require 7.5A (180/24). If your PSU is indeed maintaining 24V under load you may well be stressing that beyond its rating. Where it gets more complicated is if the LEDs are being driven by a constant current driver rather than just being connected directly across the supply. In this case, if you haven't adjusted that current, then the LEDs will still be being supplied at 5Amax so there'll be no harm done. And if the new LEDs are more efficient than the old ones you may still get an increase in brightness despite the fact that you are running them at less than their rated current. Do you still have an old one for comparison? If so it would be worth measuring the INPUT current (i.e. the mains supply current) as that will give you an idea of the total power being supplied by the PSU.
  8. The device Sunray pictured is an IEC inlet with an integrated mains filter. He's recommending that you replace the existing inlet with one of these but that will depend on whether there's space inside your unit. Do you have any idea very roughly how frequently this sound happens? You just put "every so often" but are we talking about once or twice in a week of use or once or twice an hour (or minute!) I'm finding it hard to think of ways you can get a single "crack" with a long delay before the next one, other than some sort of static buildup or leakage charge which eventually arcs over. Any idea of timings? And a fuller description of the sound too - is it literally a single crack or is it more of a fizz taking maybe a quarter of a second or more?
  9. It sounds like two problems to me : the in ear monitor side of it (of which I have little experience) and the track(s) that you play through it. For the purpose of giving them a note I suggest using the stereo track option suggested above but rather than just a click track you play the first few bars of the song before the proper playback starts. A bit of judicious editing with Audacity (which is free so fits within your budget) and you can synchronise it to the main playback. You could even record the MD giving a verbal "1, 2, 3, 4" mixed on top of it. And if there are parts of a song where they have difficulty remaining in time or pitch the MD can come in again with more prompting. So you end up with a stereo track, one channel has the audience playback and the other has all the added bits. It all depends on how well the IEM is accepted (which I think would be the bigger hurdle).
  10. DrV

    X32 Problem

    I do quite a few SMPS repairs (fewer nowadays) and I also absolutely hate bangs but they can be avoided. If you remove the main switching transistor you can check that the control chip is producing a switching waveform without even connecting the mains by simply connecting an external supply to its Vcc and Gnd pins. You can put the mains supply in through a light bulb current limit (very old skool!) and wind it up slowly with a Variac. You can check components for shorts with a standard meter. Units that haven't actually gone bang in the first place are a bit easier as it's often the startup circuit for the chip that fails. Where the main switching transistor has popped just assume that the control chip will have died too and if it has then things like gate drive resistors have usually gone in sympathy. I'm not going to try and teach anyone to fix these - everyone has their own tricks, but generally there's a lot you can do without risking a bang.
  11. DrV

    Sennheiser cables

    You can check the size of a hole by putting the shank of a drill into it. You don't need every size eg. If a 2mm drill fits quite easily but a 2.5mm doesn't then it'll be 2.1mm. Similarly between 1.5 and 2 will be 1.7. Having determined what size hole you have you can apply the same logic to measuring the size of the pin. The outer part you can measure with a Vernier caliper (probably my most used measuring tool) or a micrometer. Don't have to use drills of course - cores of solid mains cable can be used but you have to calculate or measure them (Vernier again).
  12. DrV

    Sennheiser cables

    It'll be the centre pin. The outer almost always makes contact because it's a spring but the pin and the sleeve into which it fits are (usually) solid. Do what sandall suggested and replace it.
  13. Up to you but I wouldn't worry about a few kinks, provided it runs through everything smoothly. If it were supporting something that would be a different matter. And because it's permanently under tension the kinks don't really matter if you've got them straight before you wind it on.
  14. Knew I'd seen this somewhere... https://hallstage.com/wp-content/uploads/How-To-Cable-Winch-Operated-Tracks.pdf The key to making it as easy as possible is to detach the cable that goes through the little hole at the front end of the spiral (near the handle) and leave the rear one in place. Compress any tensioners that there are on the pulleys. Then wind the rear cable on by rotating the handle. Hold the handle in place and wind one or two turns of the free end of the cable (that should be all that's left) onto the front end of the spiral so that you end up with just enough cable to thread through the other little hole and into the other clamp. Get as much tension as you can into the cable before doing up the clamp. Run the tabs open and closed a couple of times and try to get a bit more tension into the cable. Once you've got the cable as tight as you possibly can, check your clamps are tight then release the tensioners.
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