steefdebruijn

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About steefdebruijn

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  1. Ha! I knew that formula but didn't know if and how it could be put to use here :-) 3.9R gives me 166mA then. Should be enough for Megatron
  2. Thanx @mypasswordis. I will use Kevin's suggested ones then. I have lowered the current limiter to 3.9R. Should that be enough? (how to calculate this value?) Steef
  3. About load resistors to test the HV and LV sections of the PS. @kevin gilmore has stated somewhere in the Carbon thread 16K / 20W for the HV (per rail) 500R / 2W for the LV Can someone explain (or are these only valid for Carbon loads)? If I use 450V @ 150mA (to test with slightly higher load) I get values of 3K / 70W per rail (or two of 1.5K / 35W in series). If I use 12V @ 800mA (somewhat higher load) I get values of 15R / 10W per rail What am I missing? Tia Steef
  4. Package received. Thanks!
  5. Found another trafo manufacturer in Belgium (just around the corner so no excessive shipping fees I presume): http://www.monolithmagnetics.com/ asked a quote for one HV/LV and two filament trafos.
  6. Thanks for the follow up. Toroidy still a candidate then. Should I run for 13, 14 or 15 VAC secondaries for 12VDC regulated?
  7. Thanks for your feedback. I agree to use a lot of trafo overhead but I just stated the trafo should be able to deliver 120mA @ 365VAC output (because higher current == lower voltage). If 20V drop is too low how much should we account for? I used the 10% variation twice because the land line (theoretically) can go as low as 10% below nominal and 10% above nominal. Maybe account for both 10% line overload AND 20% caps overhead is a bit over the top though. So, if we get a 350VAC trafo and use 25V dropout (for example) we can handle max 4% lower land line before PS falls out of regulation (350V ×,96 (4% lower land line) ×1,414 (rectifier) −25V (dropout) = 450VDC). Right? I reckon our land line is pretty stable so indeed should not be a problem. About the cap rating: with nominal output of 350V on trafo we have nominal unregulated 494VDC on first cap. That is at 89% of its max voltage rating of 550V. 'The internet' states larger margins - 20-30% - for this but the common sense here is that's overkill? With these numbers a 550V cap accounts for a max of 11% higher landline before it gets out of spec DC from the rectifiers. That indeed seems pretty unlikely. If we can feed the Megatron with +-400VDC without problems that indeed may be preferable. Are there other changes necessary besides the PS resistors and the 21k voltage drop resistor on the Megatron board to get 300VDC for the little tubes (should be lowered from 21k to about 14k i guess)? Steef
  8. please bear with me but I try to understand the trafo/cap thing on the GRHV supplies. By reading this thread and the Carbon one from which the GR supplies emerged as far as I can tell we have to consider - 1.414 factor for rectified DC - minimum of 20V drop voltage across the regulator - 20% headroom on caps rating to assure long life - account for 10% max fluctuation of land line (230V here; governmental docs here confirm this) For 450V output I calculate 450(output) + 20(drop) = 470VDC prereg minimum / 1.414 = 332VAC minimum + 10%(max line flux) = 365VAC nominal output from trafo @ 120mA (which is the current the Megatron draws I read correctly). For the prereg cap we should use the max values. So 365VAC nominal + 10%(max line flux) = 402VAC max * 1.414 = 568VDC max prereg DC. Accounting for 20% overhead on caps to assure long life we come to 680V rating on the prereg cap. Am I way too conservative here, missing something or clearly not knowing what I am talking about? Steef
  9. I am very curious about your findings. Thanks in advance for any feedback on this.
  10. With these quotes and potential problems it is almost more beneficial to just get the Antek trafos and ship them to the Netherlands for the premium price. No fancy box to put on top of the case though... (and no 13/14VAC ones, just 15VAC so more heatsinking for the LV supply)
  11. I have a quote for the following custom trafos from toroidy.pl TS250VA PRI: 2x115V SEC: 2x 350V (300mA) 82/137 EUR/pc TS50VA PRI: 2x115V SEC: 2x 6,3V (3A) (note: with reduced off-load voltage) 26/68 EUR/pc Ex shipping etc etc of course. They can be delivered in audio grade (first number) and/or SUPREME grade (second number). I am thinking about the HV and two filament trafos in SUPREME grade on top of the chassis behind the tubes and the other three trafos in audio grade inside the chassis. Still pondering on the LV section; <learning mode>18-0-18 seems way too much for a +-12VDC output. Even 15VAC input (centertapped or dual-winding) seems a bit high for +-12VDC output. I selected the NJM7(8|9)12FA and if I read correctly they have an optimal input of 19V and a minimum of 14,5V. This suggests a trafo of 14VAC sec.</learning mode> Anyone interested in toroidy trafos (though it may be more economical to order directly from them because of shipping rates)? Ideas about the LV trafo? Steef
  12. Hi, I have a quote on the toroidy transformers. They advise 50VA 6,3VAC (2 windings) trafo with a lower than normal off-load voltage (normal 6,67V, for this application 6,4-6,5V). Are there more people interested? For the LV I think I will settle for the 50VA 15VAC version; if I understand the calculations correctly that will give me 5W dissipation on the LM7812 (and LM7912) with an input voltage in the middle of its optimal operating range of 16-22V. Steef
  13. No suggestion (because no experience) but will investigate if these can somehow be fitted: https://www.intertechnik.com/Shop/Cross-over-parts/Capacitors/Audyn-True-Copper-Cap/_-ATC022630_1768,en,6559,53292 https://www.intertechnik.com/Shop/Cross-over-parts/Capacitors/Audyn-Cap-True-Silver/_-ATS0221000_1768,en,6226,123941
  14. Thanks again, I rephrased my quote. Will not receive answer before next week with High End Munich going on this weekend.
  15. Thanks! Asked for a quote on separate 350vac 300ma and four 6.3vac 3a trafos. All with two windings and specs per winding. Will parallel the secondaries on two of them for the center tubes. What secondary is best suitable for the LV if we use 12vdc output? I would guess 12vac would be enough but maybe it does not provide enough headroom. Also no other mods necessary to the LV than using 78(79)12 instead of the *15 ones? (I think remembering from GRLV discussion that also zeners had to be lowered but maybe that is not applicable here) thanks for all your input and feedback! Steef On sockets. Will these do? http://www.jakeband.it/sockets.html