A60(+) Amplifier. Build this?

[htsz2006]

Thank you Paroxod4,
Now I translated your post...🙂I guess I should measure the capacitance between the base and the emitter of the transistor as in you picture...

 

[Berlusconi]

I have a multimeter at work. It can measure capacitance. Not sure what capacitor to measure..

Thanks!
Now, lets do this step-by-step' systematically. You should first de-solder these terminals with pins. I don't understand why they used that type of connectors in the first place. To remove terminals without damaging board use technique shown in the video below. Just learn, don't do anything on the board, just make sure you understand and know how to do it.
Also, take a photo of your transformer and share it with us here.

 

[htsz2006]

Hello! Thanks for your time! I guess they have used this kind of terminals because it is time-saving if they test them...plug and play and they have the Q.C. sticker on the board, so the boards should be tested...🙂

 

[htsz2006]

This is my transformer. I have always liked toroidals. Maybe I will upgrade it...it is supposed to be better. Does someone tested the difference in sound quality between toroidal and this kind?
It is powered on by this softstart...

I have used this transformer to power a TDA7293(perhaps fake one-because of the price...) based board and it sound like my KENWOOD KRF-X9060D
amplifier. I did not perform extensive comparisons...just left channel Kenwood, right channel TDA7293 board...powered by the below transformer 20-0-20 did not hear difference at low power..This transformer makes some noise...do toroidals makes this kind of noise..or are they silent?

 

[Berlusconi]

they have used this terminals because it is time-saving if they test them...

I guess so.
Just remove them carefully and provide a photo or schematics of yout transformer.
You will need additional transformer for on-board speaker protection 230VAC to 2X12VAC. 10 VA should be enough. Look at the attached data sheet.
Meanwhile, prepare bulb protection for testing purposes. Here is how.

 

[Berlusconi]

To help you select transformer for speaker protection, look at this:

 

[htsz2006]

Hello! Thanks for your guidance...
The photo of my transformer is at #924
I have measured the capacitance between base and emitter of the desoldered perhaps fake Toshiba 2sc5200 and the result is 6.16 nF. Can this be used without catching our house on fire?🙂 Or shall I return the product?
I have already ordered the transformers and I have read about the bulb protection, i will prepare the setup, I also have
https://eur.vevor.com/variable-tran...Kh92bQZDXQpJ0-OAbZLy6f82gAiAlSuRoC4ZEQAvD_BwE
(I use it to power my big fan...at lower voltage and rpm...)
i guess i could use the variable transformer to power at lower voltage the 33-0-33 transformer?

..thanks again for your help..

 

[Berlusconi]

Be carefull with speaker protection transformer it should be with two separate secondaries. There is another type. center tapped seccondaries. That kind if transformer will cause hum.
This is correct:

This is wrong:

 

[htsz2006]

Hello! I have ordered 2 separate transformers so it should be ok, I hope the 5W will be ok. 150W light bulb in series with the main power done according to post #925. Thanks to Berlusconi for that too...
Should I put thermal paste under the transistors and which brand?

 

[Paroxod4]

htsz2006 You are a good guy but I would recommend reading the whole thread. The questions and answers are all here. I don't think anyone will have time to repeat what has already been published many times, no offense intended.😉

 

[htsz2006]

Sorry, I have read all posts 2 times, but I do not remember everything...I will use the search.
Thanks again for all your help!

 

[Paroxod4]

Find assembly tips from Berlusconi. He has everything written in detail. Of course, there is a lot of information and it would take a long time to repeat, don't be offended. If there is something specific and unclear to you, we will of course help. But what paste and what to attach transistors to can be looked up on the Internet. I attach through aluminum oxide plates, I think that's what it's called, with thermal paste.

 

[htsz2006]

Hello!
This electrical isolation and thermal conduction is an interesting topic...I will research this more...
I have found some information about thermal insulators...Berlusconi wrote that alumina is a good one(thermal conductivity 28w/mK), so far it looks like it is the best by a lot...
If someone knows where to buy good ones, please share
I have found this..0.63mm and 1mm thickness, in theory 0.6mm would result in better heat transfer...but they do not list specifications
https://www.aliexpress.com/item/330...rl=scene:search|query_from:#nav-specification

Or this(but I have never bought from Russia...and now I do not know if I can buy...)
https://discountsell.ru/product/315765727297

 

[htsz2006]

I have measured the weight of one transistor...it is close to the weight of an original one= 9.75g

fake weight 7.2g according to youtube video

original weight 9.32g

mine possible fake 9.45g-because the inscription is not as it should be.

 

[htsz2006]

Is this ok?
https://www.aliexpress.com/item/100...uery_from:pc_web_image_search#nav-description

 

[Paroxod4]

I put all transistors on a 1mm thick plate with thermal paste, observing the dimensions. The weight of the transistor is normal, but this is China, I already wrote about the original, it has a different font and markings. I hope it will work.According to the datasheet, 9.75 grams were the first. Technologies change and become cheaper. Fake ones are usually below 8 grams.

 

[Paroxod4]

Go to Aliexpress in your country. There are many of these insulators there. Choose a good supplier and buy. Thermal pastes are different, I use Russian KPT-8. Look in your city, there are no problems.

 

[htsz2006]

Hello! Thanks for your information. I have found KPT-8 on aliexpress but does not deliver to Romania. I think I will use this thermal paste https://www.deepcool.com/products/Accessories/ThermalPaste/2021/11873.shtml.

Or this
https://www.arctic.de/en/MX-4/ACTCP00008B
But the thermal conductivity is not really specified...? I guess many products claim better values for profit..
Sadly, it seems that this false advertising is present in every industry...you cand hardly find out the truth. Only if someone test something you know.
Thanks again for all forum members who tests things and shares the truth and their experience with the ones who know less....🙂🙏

The best thermal paste types are electrically conductive, not good for mounting transistors.
If I mount the npn es pnp transistors on different heat sinks and isolated from the ground, could I use electrically conductive thermal paste?
How much poaste should I buy for the 32 transistors?
Thanks in advance!

 

[Paroxod4]

Any thermal paste will do, don't take an expensive one, but not an electrically conductive one. A thin layer on the aluminum oxide plate on both sides and press the transistor without fanaticism to the radiator. Be careful, don't split the plate.

 

[htsz2006]

Thanks, for you info.
Yes, these paste can get quite expensive, perhaps it could cost more than the board...🙂
But I can't estimate how much to buy. Can someone give me and estimate of the required paste in g for the 32 transistors?