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  1. Replies
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    I think that the Wa,g2 limiting value is intended...

    I think that the Wa,g2 limiting value is intended for UL applications; for this Hiwatt it's the Wa 'plate only' limit of 25W that's relevant.
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    392

    When reading Aiken, it can be helpful to bear in...

    When reading Aiken, it can be helpful to bear in mind that he's a Marshall guy, and when he talks about power tubes / amps, he's usually coming at it from an EL34 or 84 perspective.

    Something to...
  3. The 2 resistors form a potential divider, in the...

    The 2 resistors form a potential divider, in the same way that a regular volume control is a variable potential divider https://en.wikipedia.org/wiki/Voltage_divider.
    I wouldn't remove the resistors...
  4. 'Fraid not, there's negligible signal attenuation...

    'Fraid not, there's negligible signal attenuation across R117, so reducing its value will not result in any perceivable increase in sensitivity.
    However, there's some heavy attenuation at the power...
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    530

    If using a 100:1 scope probe, it's possible to...

    If using a 100:1 scope probe, it's possible to see the massive kV spikes on power tube plates of an amp overdriven into an inductive load; my concern is arcing across the switch body between the...
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    At idle maybe; it may cause problems if the...

    At idle maybe; it may cause problems if the switch was flipped whilst under load.

    My concern is that at high signal levels there are kV between the power tube plates of inductively loaded amps;...
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    Toggle switches aren't a good idea; too easy for...

    Toggle switches aren't a good idea; too easy for it to get knocked inadvertently, with potentially disastrous consequences; unless it's mounted internally, which would defeat the purpose.
    Schurter...
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    367

    That seems normal; there's no reason to suspect...

    That seems normal; there's no reason to suspect the OT is faulty at this stage.

    Consider that if both plates are at 490Vdc, the difference in winding resistances is having a negligible effect, at...
  9. The parameters of ecaps that fail with age / use...

    The parameters of ecaps that fail with age / use are ESR and leakage resistance. Unless you have checked those your testing was insufficient.
  10. How exactly did you check the caps? eg ESR...

    How exactly did you check the caps? eg ESR assessment.
    Schematic file or link?
    If no schematic available then best to raise another topic in that regard in the ‘schematic request’ sub forum.
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    Copper’s resistance temperature coefficient...

    Copper’s resistance temperature coefficient looks to be 0.393% / degree C, so an increase of nearly 64C would raise resistance 25%.
    Not sure but it seems feasible that even old school paper and...
  12. Replies
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    My preferred tube info search page...

    My preferred tube info search page https://bms.isjtr.ro/search.html
    Don’t even need to hit ‘return’!
  13. Thread: 6P14P-K

    by pdf64
    Replies
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    724

    If we’re happy that 6L6GC have a 30 watt plate...

    If we’re happy that 6L6GC have a 30 watt plate (design max), then el84 plates are beefier than 12 watts (design centre).
    As a reference point, 6V6 are 12 watts design centre, 14 watts design max. ...
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    Yes, fully bypass the shared cathode resistor, it...

    Yes, fully bypass the shared cathode resistor, it should be a quick easy comparison.
    It shouldn’t alter the gain and upset the balance because in normal use, within the linear range, the equal but...
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    Try making the paraphase shared cathode fully...

    Try making the paraphase shared cathode fully bypassed to see if that helps. Beyond the linear range, a positive local feedback loop somehow can get created there, causing horrid parasitic...
  16. That's fine, we've all done stupid stuff, but you...

    That's fine, we've all done stupid stuff, but you need to learn from this and accept that your thought process (to take gear off the light bulb limiter when it's obviously drawing fault current, then...
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    I find that flyback diodes tend to short out and...

    I find that flyback diodes tend to short out and cause the PT and OT to pass fault current; hence in practice they're much more of a liability than a benefit.


    Of course it may have been a bad...
  18. Thread: Modern gear....

    by pdf64
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    I think it's Ulrich Neumann (who's a member here)...

    I think it's Ulrich Neumann (who's a member here) https://www.amazon.co.uk/Guitar-Amplifier-Overdrive-Ulrich-Neumann/dp/132959665X
  19. It's not too big or invasive a job to fit such a...

    It's not too big or invasive a job to fit such a fan on to the amp chassis, see http://www.blueglow.de/FenFan.html for how it might be done.

    Nearly doubling a cathode bias resistor value is a big...
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    Exactly which model of twin reverb? With the...

    Exactly which model of twin reverb?
    With the classic type, the V3 cathode bypass cap is simple to lift one leg of; that will noticeably reduce the reverb drive level and also make the driver much...
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    It's worth giving the OT a close examination,...

    It's worth giving the OT a close examination, there may be an unused 8 ohm wire or terminal available.
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    Don’t Hammond make a replacement PT for the RI?

    Don’t Hammond make a replacement PT for the RI?
  23. Replies
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    Wow that’s cheap! The existing wiring should be...

    Wow that’s cheap!
    The existing wiring should be fine, just swap in another speaker. Careful when removing the female spade connectors, you don’t want to force things and have them open up, thereby...
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    I don't see any point in idling them any hotter...

    I don't see any point in idling them any hotter than any other 6L6 type tube in a BF type power amp, ie 30mA cathode current / 6L6. All such tubes have the same bogey characteristics.
    Why should...
  25. https://echa.europa.eu/substances-restricted-under...

    https://echa.europa.eu/substances-restricted-under-reach
    See cadmium sulphide
  26. Sticky: But unless you’ve also got the spec for the stock...

    But unless you’ve also got the spec for the stock OT, in regard of this issue, the spec of its replacement is of no benefit.
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    I've never tried one out, so thanks for the tip....

    I've never tried one out, so thanks for the tip. Any model you'd recommend? Do they create a notchy dead zone in the trem arm movement? I've been put off them by the fear that they will make subtle...
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    There are some good tips on the Kinman site that...

    There are some good tips on the Kinman site that worked pretty well with my strat. The key for me was having less than 1 turn of the string on the tuning peg.
    ...
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