1176 Rev A Output Transformer Windings

[Spencerleehorton]

Hi,
I have question for you all.

The standing DC current through Q6 is determined by the voltage on its emitter divided by R32 (39ohms), assuming that the transformer winding connected to Q6 emitter has zero resistance. If you work this out you get 56mA.

The voltage across Q6 is about 25V. This results in a dissipation in Q6 of 1.4W which it cannot deal with and gets very hot, resulting in thermal ranaway and burnt out R32.

If the resistance of the transformer winding connected to Q6 emitter is something of the order of 150ohms the working conditions of Q6 become much more sensible, with a standing current of about 12mA (2.2V/189ohms) and a dissipation of 300mW (25*.012).

So my question is, can anyone tell me the total winding spec. for the output transformer, particularly the details of the winding connected to Q6 emitter, particularly its DC resistance?

Regards

Spence.

 

[moamps]

...The standing DC current through Q6 is determined by the voltage on its emitter divided by R32 (39ohms), assuming that the transformer winding connected to Q6 emitter has zero resistance. If you work this out you get 56mA.
The voltage across Q6 is about 25V. This results in a dissipation in Q6 of 1.4W which it cannot deal with and gets very hot, resulting in thermal ranaway and burnt out R32.

2N3053  can withstand this dissipation if it is properly cooled.

.....So my question is, can anyone tell me the total winding spec. for the output transformer, particularly the details of the winding connected to Q6 emitter, particularly its DC resistance?

The feedback winding has few ohms IIRC.

 

[Spencerleehorton]

Could you be a bit more specific or scientific perhaps please? how many ohms exactly?

regards

Spence.

 

[moamps]

... how many ohms exactly?

1.65 ohms

 

[Spencerleehorton]

hi,

so the 1.65ohm is the grey/violet winding or the other wht red/wht blk winding?

Also are the other windings about 45ohms?

regards

Spence.

 

[Spencerleehorton]

After a fair bit of playing rand I've settled on this design, 600R windings turn out at about 145 ohm.

 

[Spencerleehorton]

well that didnt work either. back to drawing board!!!

 

[Spencerleehorton]

right i've managed to suss this out a bit more now, just only getting about 3H inductance so need to try a few more things out.
getting lots of hiss?
and the unit seems to be compressing but when plugging a bass in its not doing what it should.
lots of distortion when it should be compressing as well?

any ideas anyone?

regards

Spence.