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  1. Replies
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    It looks like a Jeffery circuit arrangement: ...

    It looks like a Jeffery circuit arrangement:

    https://www.americanradiohistory.com/Archive-Wireless-World/40s/Wireless-World-1947-08.pdf
    ...
  2. A quick look shows the LFO stage is modulating...

    A quick look shows the LFO stage is modulating the B+ supply to V2, which has both triodes in cathode follower config, as well as modulating the voltage at F. The V3 triode connected to V2 circuitry...
  3. The other aspects worth considering are the max...

    The other aspects worth considering are the max voltage anticipated across each cap in operation, and whether the amp has any existing bleed resistors for B+ (or whatever these caps are for), and the...
  4. Apart from possible motorboating due to poor...

    Apart from possible motorboating due to poor filter capacitors, that low frequency oscillation/peaking/motorboating is typical of feedback amps whereby the feedback rolls off but leaves a small range...
  5. DC bias imbalance in the OT primary half windings...

    DC bias imbalance in the OT primary half windings can significantly increase distortion at low frequencies in hi-fi amps. At some point of imbalance that may well become noticeable and may partly...
  6. Just read through a very interesting paper that...

    Just read through a very interesting paper that provides some example measurements that support the likely survivable level of turn-on peak voltage applied to a first filter capacitor....
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    I could suggest the simplest means to do heater...

    I could suggest the simplest means to do heater elevation in that bassmaster circuit is to disconnect the heater CT from the 0V ground, and connect the CT lead to say a 63V electrolytic positive...
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    I'd suggest posting a link to the entire amp...

    I'd suggest posting a link to the entire amp circuit - that will help identify where you what to go and what it will affect. This snips don't show what HV you are using, or where in the heater...
  9. Yes if filter and coupling caps have no leakage,...

    Yes if filter and coupling caps have no leakage, then at power on all those caps are likely to see max B+ across them unless the amp includes some bleed resistance down towards the preamp stages and...
  10. Yeh the electrolytic app guides have been quite...

    Yeh the electrolytic app guides have been quite devoid of good insight about over-voltage operation - but the Nichicon guide that Ian posted shows an informative Fig 2-4. A manufacturer will set the...
  11. I would suggest the query needs some more flesh...

    I would suggest the query needs some more flesh with respect to the amps you intend to use the caps in. I'd anticipate that the ripple current in many valve amps is substantially below the ripple...
  12. Perhaps try and get a few more measurements...

    Perhaps try and get a few more measurements points in open-loop first - see if you can get a gain value for 90deg, 135deg, and then see how your brain copes when trying to record values if the phase...
  13. Yes the typical bias supply circuit powered from...

    Yes the typical bias supply circuit powered from a HT tapping can allow a charging loop to still exist if a CT fuse blows - and that charging loop can cause the bias filter capacitor(s) to exceed...
  14. Fuses can be purchased with pigtails (for pcb...

    Fuses can be purchased with pigtails (for pcb mounting).

    The contact surface area made by most fuse holders with miniature cartridge glass fuses would have to be insignificant for valve amplifier...
  15. A circuit configuration like that needs a variety...

    A circuit configuration like that needs a variety of situations to be assessed, and there also needs to be some definition of what the load or loads are.

    For example, it could be powering a valve...
  16. All parts have their own failure modes and...

    All parts have their own failure modes and failure rates. There is no general comment that is applicable here. Understanding comes from assessment, so it would be good to locate the...
  17. Correct - and is why adding ss diodes in series...

    Correct - and is why adding ss diodes in series with valve diodes is so worthwhile, as the ss diodes pretty much eliminates valve diode arcing and failing, and the collateral damage to the PT that...
  18. I would recommend using 2x 1N4007 for each 'ss'...

    I would recommend using 2x 1N4007 for each 'ss' diode, without any additional balancing parts - with the proviso that your 1N4007's were bought as a single batch of new parts (ie. not the dregs from...
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    Just to add a bit on why humdinger pot can...

    Just to add a bit on why humdinger pot can sometimes be a benefit - the input grid is a high impedance circuit and can easily pick up hum through capacitance coupling from each heater wire. Some...
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    Nowadays there is also the option of using a...

    Nowadays there is also the option of using a small cheap dc/dc converter for powering preamp heaters from an unregulated dc supply.

    The convert could be a step up type, as per from raw 7Vdc with...
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    The hassle with diy'ing an AC mains powered...

    The hassle with diy'ing an AC mains powered switchmode (even using Vicor style parts), is that it is up to you to ensure the power supply is compliant to local safety regulations. That is especially...
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    For B+ supply, the most recent step-up dc/dc I...

    For B+ supply, the most recent step-up dc/dc I used has an isolated secondary, although I connected the primary and secondary circuits to the same 0V ground, but....

    One issue you may need to...
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    That particular unregulated dc/dc step-up module...

    That particular unregulated dc/dc step-up module has only minor sag with B+ load variation. But its B+ output also varies directly with input DCV, so any minor sag on the 12V supply effectively...
  24. I have used that module to transfer 12Vdc to...

    I have used that module to transfer 12Vdc to 6.3Vdc for heater powering. That type of buck converter has been used for decades because it can be made to transfer power very efficiently. I guess the...
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    A number of people have had threads on various...

    A number of people have had threads on various dc/dc obtained via ebay. I guess a concern is that these are not 'stock' items, so fine for diy but no guarantee on availability or quality.

    Some...
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    It seems to be a flyback configuration, and they...

    It seems to be a flyback configuration, and they have scratched off the IC labels (not an uncommon practice).

    It seems like a switchmode controller regulation issue - perhaps from too noisy a...
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    Yeh a bit off topic, but I had a few spare dual...

    Yeh a bit off topic, but I had a few spare dual gang pots so was wondering how I could use a spare gang to 'enhance' the tone function. My evil thought was to use the CW end of travel to act as...
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    One not-so-common use of bootstrapping is to...

    One not-so-common use of bootstrapping is to raise the gain of a pentode stage. Most find that an input pentode stage has too much gain already, but I wanted to see if I could get a minimalist 3...
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