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    A few years ago I was in a research post and lead...

    A few years ago I was in a research post and lead officer assessing the likely impact of Avian Influenza, which was seen at the time as as having a high likelihood of becoming a pandemic with high...
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    There's no way of knowing though how many people...

    There's no way of knowing though how many people have become infected, but show only mild symptoms and don't seek medical assistance. It could take a longer time to establish the true mortality rate...
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    The deaths numbers though are skewed by the...

    The deaths numbers though are skewed by the underlying mortality rate of the population group. That is, those people who would have died anyhow. The death rate in China is roughly 7.5 people per 1000...
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    One of the crap jobs is to remove a 3PDT switch...

    One of the crap jobs is to remove a 3PDT switch that's a press-fit in a double sided PCB before being soldered in with unleaded.
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    My thought with repairing an amp is to repair it,...

    My thought with repairing an amp is to repair it, not modify it along the way. Say you add capacitance and the rectifier fails - then you don't know if the added capacitance stressed the rectifier,...
  6. I wouldn't replace a component with one of a...

    I wouldn't replace a component with one of a different value just because it maybe looks wrong as the amp could have been running with this value for decades. If it's in a dropper string then 22k...
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    Sorry - I transposed the digits - I;ve edited my...

    Sorry - I transposed the digits - I;ve edited my post and the part you've quoted is correct.

    Set your DMM to diode mode as a more reliable way to test the transistor;
    ...
  8. Can you post some pictures of the adapter and...

    Can you post some pictures of the adapter and lead? A tingle is normal with an ungrounded Macbook, but a shock or tripping of the breaker is not normal at all. The problem with aftermarket power...
  9. I'm not clear - do you have two different...

    I'm not clear - do you have two different adaptors? you mentioned magsafe (macsafe) as well as a no-brand replacement.

    When you said you used the Magsafe adapter with a 3-pin outlet, did you use...
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    Dave Green at Ashdown recommends replacing the...

    Dave Green at Ashdown recommends replacing the 2SA1695 with 2SA1294, and the 2SC4468 with 2SC3263 in these amps whenever the originals short. While the amp is without its output transistors it's also...
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    His last activity here was in 2013, so he's...

    His last activity here was in 2013, so he's perhaps unlikely to see your request. Maybe try a P.M. and see if that gets to him.
  12. Is your power supply a genuine Magsafe? If not,...

    Is your power supply a genuine Magsafe? If not, what is it?
  13. Why not relocate the FET to the grid?

    Why not relocate the FET to the grid?
  14. I use something similar called Tectyl to prevent...

    I use something similar called Tectyl to prevent winter salt corrosion on cars and bikes, and some other outdoor stuff prone to rain exposure or workshop equipment subject to condensation.
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    Check the screw terminals on the boards - they...

    Check the screw terminals on the boards - they come loose after a while. The input and output level pots get really flaky - check these. A fried transistor stays fried and won't cut in or out with...
  16. I don't like silicone grease near contacts. It...

    I don't like silicone grease near contacts. It migrates, causes problems with resoldering and can prevent non-wiping contacts (such as found in rocker switches) from making contact. I prefer RS...
  17. CTS pots use a lot of interchangeable parts and...

    CTS pots use a lot of interchangeable parts and are easy to fix and service. I regularly rebuild them and swap donor parts from other pots to keep them going. So, yes - we need to know what's wrong...
  18. If you have some household ammonia you can dilute...

    If you have some household ammonia you can dilute it a little and use a q-tip to see if it removes the discolouration. If it does I'll bet the contacts are silver plated.
  19. It looks like silver sulphide, which initially...

    It looks like silver sulphide, which initially forms a yellow and blue rainbow-type discoloration and then eventually turns black. Note that the areas around the solder joins are protected with flux...
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    That's what I referred to as well.

    That's what I referred to as well.
  21. I've used RTV and it works fine. Even a thin...

    I've used RTV and it works fine. Even a thin piece of card or plastic wedged in if the gap is large - anything to stop the transducer from moving. It also can give can give an improvement in the...
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    Unless I've misinterpreted post #5, I think Enzo...

    Unless I've misinterpreted post #5, I think Enzo meant the same RC pair I was thinking - the ones that sit right across the amp output. The ones you refer to in the latest schematic are on the input...
  23. Sometimes it helps to put a dab of hot melt on...

    Sometimes it helps to put a dab of hot melt on the transducers if they're a loose fit. Also, a couple of drops of water-thin superglue on the edge of the winding wrap so that it gets pulled in and...
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    A failing component doesn't need to get obviously...

    A failing component doesn't need to get obviously hot to give thermal problems. Bias will drift slightly, and I always re-check after 20 minutes or so to be sure an amp is OK when warmed up, but...
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    Measuring AC at idle means oscillation. DC offset...

    Measuring AC at idle means oscillation. DC offset is OK. Are R18/C16 and their solder joints OK? I would disconnect PL1 and ground the input to the power amp to see if the problem still persists.
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    Even a cheap DMM has a resolution of 0.1mV....

    Even a cheap DMM has a resolution of 0.1mV. That's accurate enough for me for setting bias. The other way is to set it off mains current draw - turn the bias right down and then carefully increase it...
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    Also, plug your guitar into the 'Power amp in'...

    Also, plug your guitar into the 'Power amp in' socket and see if you get a clean sound. The controls won't work, but you're looking at this point to see if the power amp section is working as it...
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    I think it's perhaps instability, but I just...

    I think it's perhaps instability, but I just looked back through my notes and saw that the 220n cap in the output network can go open and the inductor solder joints crack so maybe the circuit is OK...
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