Burnt Propeller Project Board USB - anyone?

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  • When I was at Ft Monmouth I build an audio amplifier using 807 (ya, I know) output tubes. They had plate caps, so about 400 v exposed (ya, I know). ZAP!
    Re-inventing the wheel is not a waste of time if, when you are done, you understand why it is round.
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  • What do you mean? One of my favorite tubes is the 807.

    My all time favorite tube possession was a pair of enormous U19 rectifiers. Good for 2.5KV ! Sadly I don't have them anymore.

    http://www.r-type.org/exhib/aai0146.htm
  • ErlendErlend Posts: 544
    edited February 1 Vote Up0Vote Down
    this is going viral...

    At 11 I cobbled together a headset out of some metal band and two (old fashioned) telephone speaker inserts. Then I put it on my head and went on to connect it somwhere in the audio circuitry of a (valve based) radio receiver (tuned to Radio Luxemburg). I must have connected to the wrong place, because my head was hit by jolt, which I found out later must have been the 300 DC system. Fortunately my bed was just beside me, because I was thrown into it and only woke up 20 minutes later, when my mother came to investigate the silence. Obviously I did not tell her what had happened until many years later. But it took hours before I recovered.
    This event might explain if I appear strange sometimes...

    Erlend
    21st century - when everything changes
    "Better with a DAT and a COG than with a CAT and a DOG"
  • Hmm...An old friend of mine attributed his weirdness to having stuck his tongue into a light socket hanging over his bed at a young age...
  • At school (first year electronics), one of my co-students connected a 12V transformer to the mains, as we all did.. except that he connected it backwards: the 12V side to the mains, instead of the 220V side to the mains. Then he grabbed both of what he thought were the 12V wires, one in each hand. He flew several meters back.

    He definitely didn't seem to be "all there" the rest of the day.
  • If you want to experience an impressive reaction try backing into a spark plug on a small IC engine.
    In science there is no authority. There is only experiment.
    Life is unpredictable. Eat dessert first.
  • On a coincidental note, my brother in-law gave me a plasma TV, it went out on the original owner who gave to him, he had it repaired for $300, and it lasted for less than a year. Power supplies everywhere, the word plasma makes me think HV. I have never looked into one of these, always went for LCD.
    I wonder if something in it keeps a charge?
  • Plasma tv's do need a higher voltage to ionize the gas. Not sure of the exact voltage but it is lower than the 25KV or so of CRT's. Probably less than 200V for a plasma tv.
    In science there is no authority. There is only experiment.
    Life is unpredictable. Eat dessert first.
  • Kwinn, good to know, what I found on it so far relates to the power supply in the center, and also to bad cap's. It says on it 200-215V, If I can find bad capacitor's, I'll update that thread with what I found , board is only $33. But replacements aren't lasting.
    It looks like new, and would make a good display for the basement. There's no stand, so it needs mounted to the wall or ceiling. Not as easy to lug around, compared to LCD.
  • MikeDYur wrote: »
    Kwinn, good to know, what I found on it so far relates to the power supply in the center, and also to bad cap's. It says on it 200-215V, If I can find bad capacitor's, I'll update that thread with what I found , board is only $33. But replacements aren't lasting.
    It looks like new, and would make a good display for the basement. There's no stand, so it needs mounted to the wall or ceiling. Not as easy to lug around, compared to LCD.

    If you do find bad capacitors try to replace them with better quality low ESR capacitors, with at least the same and preferably slightly higher voltage ratings. Switching power supplies are hard on capacitors.
    In science there is no authority. There is only experiment.
    Life is unpredictable. Eat dessert first.
  • Perhaps the replacement boards were produced with the original production run and that's why they are not lasting.

    I was given a faulty plasma TVs and googled the normal faults. In this my model the horizontal and vertical drives were often at fault. So I checked and sure enough one was at fault. Since the two boards were almost identical I was able to meter the differences. There was a common driver module and I could tell the faulty one so I bought a new module and soldered it and hey presto, a working tv. Cost $13.50. Board cost would have been about $130.

    Have another to fix where the caps in the tiny standby power supply fail. Google says ~$6.00 for caps but I know I buy them for ~$0.50 :)

    But for these 10 year old tvs, for non-technical people, the service call and parts are not worth it.
    My Prop boards: P8XBlade2, RamBlade, CpuBlade, TriBlade
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  • kwinn wrote: »
    If you do find bad capacitors try to replace them with better quality low ESR capacitors, with at least the same and preferably slightly higher voltage ratings. Switching power supplies are hard on capacitors.



    Looks like a good time to replenish my electrolytic's while i'm at it. Here's some information on the subject I'll pass along.


    https://www.illinoiscapacitor.com/pdf/Papers/low_ESR_fact_or_fiction.pdf

    https://en.m.wikipedia.org/wiki/Equivalent_series_resistance

    Capacitors

    In a non-electrolytic capacitor and electrolytic capacitors with solid electrolyte the metallic resistance of the leads and electrodes and losses in the dielectric cause the ESR. Typically quoted values of ESR for ceramic capacitors are between 0.01 and 0.1 ohms. ESR of non-electrolytic capacitors tends to be fairly stable over time; for most purposes real non-electrolytic capacitors can be treated as ideal components.

    Aluminium and tantalum electrolytic capacitors with non solid electrolyte have much higher ESR values, up to several ohms, and ESR tends to increase with frequency due to effects of the electrolyte. A very serious problem, particularly with aluminium electrolytics, is that ESR increases over time with use; ESR can increase enough to cause circuit malfunction and even component damage,[1] although measured capacitance may remain within tolerance. While this happens with normal aging, hightemperatures and large ripple currentexacerbate the problem. In a circuit with significant ripple current, an increase in ESR will increase heat dissipation, thus accelerating aging.

    Electrolytic capacitors rated for high-temperature operation and of higher quality than basic consumer-grade parts are less susceptible to become prematurely unusable due to ESR increase. A cheap electrolytic capacitor may be rated for a life of less than 1000 hours at 85°C (a year is 8760 hours). Higher-grade parts are typically rated at a few thousand hours at maximum rated temperature, as can be seen from manufacturers' datasheets. Electrolytics of higher capacitance have lower ESR; if ESR is critical, specification of a part of larger capacitance than is otherwise required may be advantageous.

    Polymer capacitors usually have lower ESR than wet-electrolytic of same value, and stable under varying temperature. Therefore, polymer capacitors can handle higher ripple current. From about 2007 it became common for better-quality computer motherboards to use only polymer capacitors where wet electrolytics had been used previously.[2]

    The ESR of capacitors of relatively high capacity (from about 1 μF), which are the ones likely to cause trouble, is easily measured in-circuit with an ESR meter.
  • That's Equivalent Series Resistance.

    Moral of the story is use new electrolytics and keep them cool when in operation. Which can be tricky as they are often sat next to regulators and such in power supplies.
  • Cluso99 wrote: »
    Perhaps the replacement boards were produced with the original production run and that's why they are not lasting.

    I was given a faulty plasma TVs and googled the normal faults. In this my model the horizontal and vertical drives were often at fault.

    That is what I'm afraid of, getting this main PS in order is one thing. But this TV has large electrolytic's on almost every board. And one thing I do remember about Plasma TV's is they generate a substantial amount of heat. They are a current hog, this one is rated @350W. Maybe I will have to put the minimum amount of screws in the back, if I'm going to be servicing these boards on a regular basis.
    I bet this TV has less than 1000 hours use since it was made in 2009.
  • Heater. wrote: »
    That's Equivalent Series Resistance.

    Moral of the story is use new electrolytics and keep them cool when in operation. Which can be tricky as they are often sat next to regulators and such in power supplies.



    These TV's should have quiet vent fans, or at least have the heatsinks on the outside of the cabinet. It wouldn't be that hard to design the back with an opening around the parts that need cooling.
  • The culprit left his prints,

    I'm going to venture and say this board is crap.
    2656 x 1494 - 574K
    2656 x 1494 - 511K
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