P3A Problems!

[Josue Guedes]

Hello, mei first post here! I would like to ask for help to friends. I'm having trouble assembling a P3A amplifier, the transistor Q2 is hot, and I have about 4 volts DC in the output amplifier still works. What can I try to do to fix?

 

[jaycee]

Is D1 lit ? Check the values of R6 and R7. Q2 should not be getting hot at all. I'd recommend using a new Q2 when you find the problem.

 

[Josue Guedes]

Thank you for your attention! R6 and R7 are 560 ohms, D1 not lit, I am using pcb this article:

https://elprojects.wordpress.com/2014/11/21/rod-elliott-amplifier-p3a/

I'm using +/- 25 volt transformer that I have here.

 

[thimios]

Thank you for your attention! R6 and R7 are 560 ohms, D1 not lit, I am using pcb this article:

https://elprojects.wordpress.com/2014/11/21/rod-elliott-amplifier-p3a/

I'm using +/- 25 volt transformer that I have here.

Check the D1 polarity.
Post photos of your amplifier.

 

[Josue Guedes]

Good night, D1 is connected to the cathode in the -25 volt line, I'll check again! D1 is lit?

 

[de Ocampo]

An externally hosted image should be here but it was not working when we last tested it.

Not to be a skeptic but I wonder if this lay-out produces a clean sound. The location of the fuses does not look good, placing them near the input?...and stargrounding can be improved.

 

[jacques antoine]

Not to be a skeptic but I wonder if this lay-out produces a clean sound. The location of the fuses does not look good, placing them near the input?...and stargrounding can be improved.

In addition, the postioning of VAS vs. Sziklai driver recommended by R. Elliott is not respected in this layout which can result in thermal instability.

J.

 

[Project16]

In addition, the postioning of VAS vs. Sziklai driver recommended by R. Elliott is not respected in this layout which can result in thermal instability.

J.

I think with a small aluminum plate (heatsink) with Q5, Q6, Q9 would be a solution (be careful to isolate Q5 and Q6 of the heatsink).

Do you use a standard brightness LED (no high-brightness )?

 

[Josue Guedes]

An externally hosted image should be here but it was not working when we last tested it.

Not to be a skeptic but I wonder if this lay-out produces a clean sound. The location of the fuses does not look good, placing them near the input?...and stargrounding can be improved.

Good Morning! After correcting the problems will do the tests and my impressions post.

 

[Josue Guedes]

In addition, the postioning of VAS vs. Sziklai driver recommended by R. Elliott is not respected in this layout which can result in thermal instability.

J.

Initially I want to hear the result of this project. I consider buying the PCB RodElliot.

 

[Josue Guedes]

In addition, the postioning of VAS vs. Sziklai driver recommended by R. Elliott is not respected in this layout which can result in thermal instability.

J.

Yes, I can test this option! The heating occurs only in Q2, I'm thinking that the components I'm using are false. I tested a BD139 in Q2, and it was cold, I'll replace all the BC546. Thank you for opnion.

 

[Josue Guedes]

I think with a small aluminum plate (heatsink) with Q5, Q6, Q9 would be a solution (be careful to isolate Q5 and Q6 of the heatsink).

Do you use a standard brightness LED (no high-brightness )?

Led D1 is common, low brightness.

 

[jaycee]

D1 must be lit. It provides a voltage reference for Q3, which in turn sets the current drawn through Q1 and Q2. It is possible Q3 is faulty and is switching fully on. Measure the voltage on Q3's base with respect to V-, it should be about 1.7v

 

[Josue Guedes]

Good evening. D1 was reversed! I'm ashamed! All working now!

 

[Josue Guedes]

Now I need the transformer, toroid here is a fortune! common transformer has a good price! 25 + 25 Volt 12 Amp, what do you think?

 

[Ian Finch]

Why not read the recommendations of the designer? At least you will understand why certain choices are better than others and you can decide whether +/- 36V is right, is not too big and heavy, current is sufficient, hum too much etc.

 

[Josue Guedes]

Good Morning. Sorry, I did not express myself properly. In fact my question is whether common transformers are less than toroids, because in my country has low cost.

 

[Josue Guedes]

I did some auditions compared to Marantz 2226b, Diana Krall, Miles Daves, Patricia Barber, Tarja Turunem, and even with the poor supply, the amplifier was better!

 

[Ian Finch]

.....In fact my question is whether common transformers are less than toroids.....

Common E-I transformers are fine, if you bear in mind they radiate more hum and noise than toroidal, so you may need a larger case to allow spacing the transformer (and power leads) further from the amplifier. I suggest you listen to the amplifier output whilst you carefully (!) move the transformer or just the twisted leads about in the case before bolting down, until you get least noise and then fasten in that position.

If you are looking for best possible sound quality, even low noise levels become important. Otherwise, it doesn't matter what you use. Even cheap SMPS power supplies will work like any power supply if the current and voltages are adequate for peak output needs and grounding is correctly done.

 

[JMFahey]

in my country

Which is ???????
For a proper answer Forum members MUST state where they are, best answer depends a lot on that.

Fill your Country/State/City location like most of us did.