Gtlab Forum

I recently disassembled a fried simul-class OT from a 2:90.
It was marked: 562004R-1 EIA606-540

The windings were (I may have missed a turn or two since the two primaries don't match):
74 turns in two layers (4ohm)
831 turns in seven layers (Primary part 1)
42 turns in one layer (8ohm) (in series with 4 ohm)
832 turns in seven layers (Primary part 2)
74 turns in two layers (4ohm)

The two 4ohm windings were paralleled.

There were no taps on the primary, except for the center tap.

I got 0.315 and 0.8mm wire for the rewind, but both these seem to be about 0.01mm thicker than what mesa used.
I hope it fits anyway...
EI Laminations:
Measured over entire primary:
DCR 86ohm
~9H inductance
~16mH leakage inductance when shorting 4ohm tap
17.5kHz upper -3dB frequency response with 4ohm load

108 laminations of each kind measures 95.2x79.7x37.2mm assembled.

Anatoly Kotelevets' Program results:

Выходная мощность(Вт) = 10.000 W
Сопротивление нагрузки(Ом) =  8.000 R
Сопротивление анодной нагрузки(Ом) = 3600.000 R
Площадь сердечника (кв. см) =  6.250 sm2
Низшая рабочая частота (Гц ) = 60.000 Hz
Ток анода (А) =  0.140 A

Коэффициент трансформации =  0.052
Амплитуда напряжение (В) = 268.328 V
Число витков 1 Обмотки = 2290
Число витков 2 Обмотки = 119
Ток 2 Обмотки (А) =   1.118 A
Диаметр провода 1 обмотки (мм) =  0.299 mm
Диаметр провода 2 обмотки (мм) =  0.740 mm
Максимальная Инукдиция в сердечнике (Гс) = 7031.250 Gs
Толщина прокладки (мм) =  0.267 mm
 

Can you post the program?

Available wire diameters?
Primary Impedance Ra=3600 Ohm / 6000 Ohm (3600 or 6000) or (3600 and 6000)?
Secondary Impedance 4/8 Ohm (4 or or (4 and ?

That's just for 3.6K(EL34-6L6) / 6K(6V6)
I only want 3.6K/4 and 8R outputs
for primary I will use 0.3mm wire, for secondary I have 0.7mm wire.

By the way, he takes bad technical terms and the conversations

Sorry, I wasn't sarcastic, I just want to find help.
I'm from Serbia, and It's much cheaper to wound transformer, over to get one from internet.
Can somebody explain how can I determine core size form flux density(in my case 5000Gs), power(10W), low frequency(82Hz)?
Here's http://www.valveheart-bg.com/index.html

Hi Guys,
I want to build EL34/6L6 SE power amp, but I also want to wound OT.
According to Valveheart, full calculation goes like this(for my example):
Power P= 10W(3.6K EL34-6L6SE)
Low freq response fd=60Hz
Primary Impedance Ra=3600 Ohm / 6000 Ohm
Secondary Impedance Rs=4/8 Ohm
Flux density B - 10000Gauss - 1T

According to Valveheart core dimension is determinated by the eq:
Q=sqrt( (Pout*G*10^6) / (fmin*B*Is)) - where:
- Pout is the output power
- G is coefficient of weight between copper and iron /G=1.5 - 1.0/
- f min is the lowest desirable frequency
- Is is the density of current in the wire - Ampere/sq. millimeter (1.5 - 2.5 A/sq. mm).
- B is Magnetic Field Intensity in Gs
I don't get this equation cause every time I calculate it I think it's wrong.
Here's mine example:
Q=sqrt( (10*1.5*10^6) / (82*10000*1.5))=3.5cm^2
I'm confused because of the lower equation, cause for the same input I get:
Q=20*sqrt(Pout/fmin)
Q=20*sqrt(10/82)=6.98cm^2
I wonder how they got 20?Can someone explain this to me
Q=20*sqrt(Pout/fmin) - but this applies for B-5000Gauss, and that's for HiFi, we need guitar OT, so we chose B-10000, other reason is, any power transformer core can be used, cause they are made for 10000Gauss - 1T.
So we get:
Q=10*sqrt(Pout/fmin)
Q=10*sqrt(10W/50Hz)
Q=4.47cm^2 - 6.25cm^2 core we will chosen

Primary turns:
n1=10^8/(4.44*B*fmin*Q)=10^8/(4.44*10000Gauss*50Hz*6.25cm^2)=7.2
U1=sqrt(Ra*Pout)=sqrt(3600*10)=190VAC
Np= n1*U1=1368 turns

Secondary turns:
Ns4=1368/(sqrt(3600/4))=45 turns
Ns8=1368/(sqrt(3600/8))=65 turns
Ns16=1368/(sqrt(3600/4))=91 turn

Primary current:Ip=Ia+Ia'
Ia=SQRT(Pout/Ra))*1000=SQRT(10/3600))*1000 = 52.70mA
Ia'=73mA(this is bias for tube)
Ip= Ia+Ia'=125.70mA

Secondary currents:
Is4=SQRT(Pout/4)=1.58A
Is8=SQRT(Pout/8)=1.12A
Is16=SQRT(Pout/16)=0.79A

Wire diameter:
wp=SQRT(Ip*0,001/3)*1,13=SQRT(125.70*0,001/3)*1,13=0.23mm - 0.3m wire is chosen
ws=SQRT(Is4*0,001/3)*1,13=SQRT(1.58*0,001/3)*1,13 = 0.82mm - 0.7m wire is chosen

Can someone who is experienced in winding OT's can confirm this, before i start wounding the transformer.

Thanks for the bias resistor, I draw +,-30VDC on the schem, not -30VDC~GND. And, are the feedback resistors (100R) OK?

Thanks.

Hi guys, I was designing guitar amp for my self, and I need some advice from more experienced guys.
So here is the schematic, please tell me if something wrong or need to be changed?
Here are the questions:
1.Can somebody give me formula for calculating bias current of
MOSFET-s
2.Where to measure it,
3.Could somebody calculate me bias current on the MOSFET's?

Thanks

Hybrid 45W.pdf

Here is original Diezel VH4 schematic, the only problem is, there are no component values, Peter wouldn't send me ?!?As my memory recall AZG has his own, maybe he could help us?

Diezel VH4.pdf

Hi guys, I solved the problem, so here are the samples (recorded with cheap PC mic):
Ultra Sample1.mp3 - dry
Ultra Sample.mp3 - wet

Hi guys,
I made a hybrid amp. Roccaforte preamp and 100W MOSFET (TDA7294) SS amp.
I designed PCB (for the rocca and TDA):
Roccaforte Schematic & PCB.pdf
Some pics:







But I have a problem, I have noise and hum in the amp, here is sample:
Rocca Problem.mp3
and here is layout how i connected the amp,internally:
Rocca Layout.pdf

What can be the problem? Help me to solve this.