Quasimodo results (ONLY)

[JeffYoung]

This thread is for Quasimodo results ONLY.

Please NO COMMENTARY HERE. (For comments, please use the Simple, no-math transformer snubber using Quasimodo test-jig thread.)

[Note: it might be nice to highlight any non-standard Cx/Cs values in red.]

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[JeffYoung]

Block RKD 160/2X15

Cx 10nF
Cs 150nF
Rs 26Ω


[Data supplied by SGK, http://www.diyaudio.com/forums/powe...using-quasimodo-test-jig-126.html#post5206652 post #253]


Hammond 229C40

Cx 10nF
Cs 150nF
Rs 577Ω

[Data supplied by luvdunhill, post #527]


Hammond 160H12

Cx 10nF
Cs 150nF
Rs 11.5Ω

[Data supplied by luvdunhill, post #528]


Nuvotem 120VA, dual 15V secondaries

Cx 10nF
Cs 150nF
Rs 42.5Ω

Nuvotem 80VA, dual 15V secondaries

Cx 10nF
Cs 150nF
Rs 39Ω

Nuvotem 50VA, dual 15V secondaries

Cx 10nF
Cs 150nF
Rs 38.6Ω

[Data supplied by B&W_arthur, post #351]

 

[JeffYoung]

Triad Magnetics VPT30-5330, dual 15V secondaries

Cx 10nF
Cs 150nF
Rs 22.6Ω

[Data supplied by Mark Johnson, http://www.diyaudio.com/forums/powe...using-quasimodo-test-jig-126.html#post5206652 post #255]


Antek 400VA, 18v

Cx 10nF
Cs 150nF
Rs 18.3Ω

[Data supplied by rickmcinnis, post #978]


R-Core 120VA, dual centre-tapped 18-0-18 secondaries

Cx 10nF
Cs 150nF
Rs 54Ω/54Ω, 69Ω/69Ω

[Data supplied by alexkosha, post #1219]

 

[JeffYoung]

Edcor #XPWR274 (Torpedo and Torpedo III), 200V B+ and 6.3V filament

B+ Cx: 6.8nF
B+ Cs: 68nF
B+ Rs: 760Ω

filament Cx: 10nF
filament Cs: 150nF
filament Rs: 12Ω


Bottlehead PT-10 (SEX), 160V B+ and 6.3V filament

filament Cx: 10nF
filament Cs: 100nF
filament Rs: 9Ω

B+ Cx: 10nF
B+ Cs: 100nF
B+ Rs: 400Ω


Torroidy 300VA, 240V primary, dual 36V secondaries

Cx: 10nF
Cs: 150nF
Rs: 12Ω / 14Ω


Torroidy 500VA, 240V primary, dual 18V secondaries

Cx: 10nF
Cs: 150nF
Rs: 7Ω / 7Ω

 

[EUVL]

Talema 70064K 25VA 2x18V
Cx 10nF
Cs 150nF
Rs 12Ω

Talema 70061K 25VA 2x9V
Cx 10nF
Cs 150nF
Rs 7.8Ω

Talema 70043K 10VA 2x15V
Cx 10nF
Cs 150nF
Rs 12Ω

 

[paulebappie]

R-Core Selectronic 30VA 2x9V
Cx 10nF
Cs 150nF
Rs 47Ω

 

[fabrice63]

Toroidal Selectronic 220 va 2 x 18 v

Cx 10 nf
Cs 150 nf
Rs 140 Ω

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[Mark Johnson]

Theoretically it would be possible to write a software "bot" which uses the data contained within these posts, to calculate the transformer secondary's effective leakage inductance. Cx makes it both impossible, and irrelevant, to calculate the secondary's effective self capacitance.

 

[KevinHeem]

Antek 400VA, 18v

Cx 10nF
Cs 150nF
Rs 18.3Ω

Jeff,
I've tested two Antek AS-4218, and one AN-4218 using the same Cx=10nf, and Cs=150nf. I'm coming up with a way different Rs values than you have posted, but consistent between the three transformers tested. How confident can we be that the values posted in this thread are accurate? I get what you're trying to do here, but I'm encouraging others to build their own Quasimodo/Cheapomodo and verify for themselves.

 

[JeffYoung]

The reports are all attributed, so I guess it comes down to how much you trust the skill of the reporter.

But by all means build your own: I did. 😉

 

[KevinHeem]

This chart shows my results testing an Antek AS-4218 with Cx=10nf Cs=150nf and Rs=6-10Ω. I'm using 7Ω in my actual circuit.

View attachment 10to6ohm.pdf

 

[dimkasta]

A mention of the primary configuration might also be useful. From what I remember from Mark's article, the optimal point differs a bit if the primary is wired in series (230VAC) or in parallel (110VAC)

 

[andrensairr]

Harbuch Electronics I2225FAM (500VA, 240V primary, dual 45V secondaries)


Cx 10nF
Cs 150nF
Rs 19.8Ω

 

[merlin el mago]

Selectronic R-Core (120VA, 240V primary, dual 18V secondaries)

Cx 10nF
Cs 150nF
Rs 110Ω

 

[Johnny Canuck]

Primrose Audio Toroids (two) (508VA, dual 120V primaries, dual 18V secondaries)

Cx 10nF
Cs 150nF
Rs 10Ω

 

[SyncTronX]

Antek AS-4218, 400VA, dual 18V secondaries, dual full wave bridges:
(Attributed to another DIYer who requested to not use his name.)



Cx = 3.3nf
Cs = 470nf
Rs = 16.9 ohms

 

[Mark Johnson]

Posted 08 December 2018 HERE

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[audiomusica]

Talema 2x115V, 2x7V, 2x12,5VA


Primaries in series for 230V operation and shorted (for snubbing)
Secondaries in parallel


Cs=150nF, Cx=10nF -> fosc ~ 625kHz(!)



Snubbing this small print torodial transformer I get values for Rs ~ 12Ohm.


Are such low values for Rs reasonable?

 

[kamis]

Results with Cheapo Modo , ANG low profile 2x30V, 24VA, fosc 10.5KHz .
Very high 24mH inductance. Standard C values, RS 770 Ohm.

 

[Mark Johnson]

Audiomusica, since you doubt your experimental results from No-Math Quasimodo, you have no other choice than to use math for verification.

Your numerical values of fosc (6.25E+5) and Cx (1.0E-8) indicate that the secondary self inductance L is about (6.5E-6) Henrys. We calculate L using the LC resonance equation.

The LC resonance equation: 2 * Pi * fosc = 1 / sqrt(L * C)​

Plugging this value for L into equation (A.11) of the Quasimodo design note, we find

R < 12.7 ohms​

Which seems to be in broad agreement with your experimental results. You were wrong to doubt them.