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    Double check that you have the bias cap wired...

    Double check that you have the bias cap wired with positive to ground. Also, check your voltages are stable at the PSU caps rather than at the other end at the tube.
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    It's really nice to watch how that metal curls up...

    It's really nice to watch how that metal curls up off the graver and I really do appreciate the skill this takes having tried this myself. I think it leaves a strong signature - the hand of the maker...
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    That, plus maybe filtering effects of the volume...

    That, plus maybe filtering effects of the volume pot at low volume (even with a treble bleed cap) as well as the speaker cone inertia and mechanical damping that's not being overcome by the signal....
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    Try grounding V1b grid, then V1a in turn - does...

    Try grounding V1b grid, then V1a in turn - does the hum disappear?
  5. Each wire is a connection to the start and finish...

    Each wire is a connection to the start and finish of each coil. Don't think of them in terms of grounds for the coils - they only become a ground when attached to a ground point. The bare wire runs...
  6. I have some cheap crimp tools that have come my...

    I have some cheap crimp tools that have come my way over the years and also some ex-military tools as well as AMP ratchet tools. The difference in crimp quality is considerable and with the cheap...
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    The actual parameters of an output transformer...

    The actual parameters of an output transformer can vary considerably and the most basic measurement of DC resistance can be very misleading. Actual impedance values also vary with different...
  8. There's an add-on reverb for the Randall MTS amps...

    There's an add-on reverb for the Randall MTS amps that's interesting and works really well. The PCB is bolted underneath the tray in the centre with the component side uppermost an is the full width...
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    Unless independently tested I take any approvals...

    Unless independently tested I take any approvals of Chinese power supplies as meaningless. I've used these (or similar) supplies for quite a while and they've been fine. Wherever practical I install...
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    I temporarily tried star grounding and this got...

    I temporarily tried star grounding and this got the hum down to Fender Deville levels. When I put it back to stock the hum was back. I checked every connection with my low resistance meter and...
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    I spoke to Hayden (Dave Green) and he pointed to...

    I spoke to Hayden (Dave Green) and he pointed to the ground being off channel 1 volume pot shell. I then saw it relies on the crimp between the shell and the rest of the pot being good - in this case...
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    FR4 is the stuff I now use and it's superior in...

    FR4 is the stuff I now use and it's superior in every way to phenolic. The remaining phenolic sheet I have gets used up for general engineering, or building low-voltage space-charge regen radios...
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    A good number of years ago two friends along with...

    A good number of years ago two friends along with my girlfriend (now Wife) and I hired a boat to navigate the Caledonian Canal from east to west in Scotland. On the way back we ran into a severe...
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    I used to experiment a lot with high voltage...

    I used to experiment a lot with high voltage stuff - Tesla coils, Wimshurst machines and Ruhmkorff coils. One of the main issues is leakage across surfaces of otherwise excellent insulators. Dust,...
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    Some phenolic board can absorb atmospheric...

    Some phenolic board can absorb atmospheric moisture; I have a full sheet, bought new from a UK manufacturer and selected on the basis of voltage rating. The first amp build I did with it had scratchy...
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    I went to pay for some items by card yesterday...

    I went to pay for some items by card yesterday and ended up having to use cash - the shop assistant said the systems couldn't handle the transaction volumes across the country.
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    I thought of UV for banknotes. I have a handheld...

    I thought of UV for banknotes. I have a handheld lamp for curing resin that's quite powerful - it reddens exposed skin and you have to wear the supplied goggles so it may work OK. There's nothing on...
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    I would't want to wipe down a vintage instrument...

    I would't want to wipe down a vintage instrument with it, though. A poly finish would be OK but cellulose could react. For the time being I'm handling with gloves, sanitizing as much as I can and...
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    What about guitars? I take in as many guitars as...

    What about guitars? I take in as many guitars as amps and they seem to me to be a greater risk.
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    I want one with three rotating pickups. That way...

    I want one with three rotating pickups. That way if I get three cherries in a row I get a gum ball.
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    That's quite interesting. It looks like there...

    That's quite interesting. It looks like there would be a lot of tooling costs to get the mechanism to this level of fit, finish and function. I wonder how many prototypes were made along the way?
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    Yes, I removed every screw and slid plastic...

    Yes, I removed every screw and slid plastic underneath every standoff to make sure there's no contact and still get about 4 ohms to chassis. The jacks are a regular type on this amp - also removed...
  23. A 1M linear pot may be close enough to get it...

    A 1M linear pot may be close enough to get it working OK. A CTS pot may have sufficient lug length to straighten them out and bend them into the correct alignment with two pairs of needle-nose...
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    Hayden Speakeasy ground hum

    I have a Hayden Speakeasy combo in right now that's got a really bad ground hum coming from the preamp (I've eliminated heater hum). It's a difficult amp to work on due to having layered boards...
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    Further investigation shows noise is also getting...

    Further investigation shows noise is also getting picked up by the screen of the reverb cables. With my original phones used for testing I though this was a problem fixed and there was insufficient...
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    The pots ground fine. With IC6 removed and pin 1...

    The pots ground fine. With IC6 removed and pin 1 grounded the noise is still there, so the problem is after this. I've had to park it to get some other repairs done, but it still doesn't make sense...
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    I replaced IC1 and no change. I got the amp to...

    I replaced IC1 and no change. I got the amp to where I thought it was good enough and at gigging volume there was just a little bit of noise with a phone held right against the amp, but nothing...
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    I rerouted the speaker wires away from the preamp...

    I rerouted the speaker wires away from the preamp and this has the same effect in reducing the noise as the toroid. The noise is certainly being radiated internally by the speaker leads and also...
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