the power supply is still shorts out

 

Can you take a photo of it and post the image?

What were the exact part numbers that you used for the 2N2222 and 2N2907 transistors?

 

Hey,,,I ve found something new...As soon as i turn on the power supply,,,,i get the desired sine wave output but that lasts only for a few milli seconds and then the power supply starts shorting and the output distorts as well... Any idea what causes this kind of bizzare behaviour???

 

Right now im using BC639 and BC640 instead of 2N2222 and 2N2907 but the behaviour is pretty much the same....will post a pic of the breadboarding soon

 

Hey,,,I ve found something new...As soon as i turn on the power supply,,,,i get the desired sine wave output but that lasts only for a few milli seconds and then the power supply starts shorting and the output distorts as well... Any idea what causes this kind of bizzare behaviour???

Lack of thermal coupling between D1/Q1 and D2/Q2.

Low Vbe for the diodes being used. You'll need to change to different diodes.

I told you in the very beginning that thermal coupling between the diodes and the transistors was critical.
[eta]
You might be able to change over to 1N400x diodes. They will have a lower Vf for the same current.

 

Oh im sorry...i overlooked the thermal coupling bit...Is it possible on the breadboard...Hw do i do it?? is is even going to give a stable output by thermal coupling???

 

If you have some J-B Weld, that'll work - even the 5-minute stuff. You should have the diode body and transistor face held in contact with each other as the epoxy cures. A spring clothespin might do it.

 

and i decided to use 1N60S diode instead of a 1N914

 

so again,,,once i buy this J-B weld...do i join the pin of the transistor and the diode using it??

 

No wonder you're having problems.

A 1N60S is a Germanium diode.

It would have a very low Vf, and keep both transistors turned on.

You should use the L272, as you can't seem to follow any recommendations as far as discrete components.

 

Sorry i typed the incorrect name in...im using the 1N4007 and i have the same behaviour anyway...

 

Could you please explain what difference J-B weld would make and why it is necessary??

 

J-B Weld is one of the few "permanent" epoxies that are available in small quantities to the general public.

As I mentioned before, it would help a great deal in the thermal coupling of the two devices - however, you must couple them body to body.

If you are seeing the output waveform going downhill within seconds of powering on the circuit, then perhaps something else is way "out of kilter". R5/R6 may be too low in resistance.

I don't have models for the 1N4000 series, the 1N60x series, or the transistors you chose loaded into LTSpice. Your results will be difficult to predict.

If you stick with the components that were used in the simulation, you should get results that are similar to the simulation results. If you use different components, your mileage may vary significantly - up to the point of being reduced to a small pile of molten rubble.

 

Ok,,,i gave up on this circuit and now I am trying to get the power opamp l272 2 wrk...I get a the desired sine wave but it not very clean and the frequency range over which the amplitude remains stable is quite small. Im suspecting this 2 do with the low slew rate of 1v/Us of this opamp. Can any1 suggest a High speed power opamp that is affordable??

Thanks in advance.

 

Why should anyone suggest anything to you? You'll simply buy something else, and blame them for it not performing to what you think you need?

 

Hi Sgt,

I don't have models for the 1N4000 series,

Will this helps?

.MODEL 1N4001 D(Is=76.9p Rs=42.0m N=1.45 Cjo=39.8p M=0.33 tt=4.32u Iave=1 Vpk=50 mfg=Various type=silicon)
.MODEL 1N4004 D(IS=3.699E-09 RS=1.756E-02 N=1.774 XTI=3.0 EG=1.110 CJO=1.732E-11 M=0.3353 VJ=0.3905 FC=0.5 ISR=6.665E-10 NR=2.103 BV=400 IBV=1.0E-03 type=silicon)
.MODEL 1N4007 D(Is=76.9p Rs=42.0m N=1.45 Cjo=26.5p M=0.33 tt=4.32u Iave=1 Vpk=1000 mfg=Various type=silicon)

 

Hi Sgt,,,

When did I evr balme anyone?...Infact I am very thankful for all the help I got from here...If you are sick of my problems then you are not obliged to help...Il just get hlp from some where else or do something else. You do not have the right to blame me for my mistakes...It was nice knowing this forum...

Good bye.