Please:see this vintage amp PCB with TDA2020

[Peters8]

Hi guys!🙂
Please could you take a look at this amp PCB based on the vintage TDA2020:
http://pepina.org/snimki/5146220.jpg
My question is: does this PCB need a simmetrical power supply (I mean 18-0-18 Volt) or a "simple" power supply (with only the negative and positive poles)?
And if I want to get a stereo sound Do I need two of this amp PCB?
Thank you very much in advance for the help!😉
Best regards

 

[asuslover]

A simple chip power amplifier(not bridged) with a "simple" power supply( not symmetrical) will have a large capacitor (larger than 1000uf ) right before the speaker, so the capacitor will be between amp and speaker. I am not sure that I see that capacitor here but I see 2 fuses, I assume the amp uses an symmetrical power supply. I might be wrong! Unless you are trying to fix an old Reel to Reel Kashtan tape recorder, Let it GO!
I would not make a new project with this chip, low power chips are available , lm1875 is great one.
As far as I remember tda2020 is a mono chip, for stereo you will need 2 of them.

 

[FauxFrench]

I had one of these TDA2020 amplifiers I made MANY years ago. It worked for 40 years.
It needs a symmetrical 18-0-18V power supply and it is a mono (single) amplifier, so you need two chips for stereo.

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Today, the TDA2020 is rare and many modern amplifier chips perform better.

 

[ICG]

This amplifier IC needs symmetrical rail voltages. You could create symmetrical voltages from a single ended power supply, I wouldn't do that though.

 

[Peters8]

Thank you for the replies, guys!
Ok this is the missing part of that amp PCB based on the TDA2020 that the same company sells to complete the kit:

http://pepina.org/snimki/5120091.jpg

and this is the product description:

"10A power supply for MDA2020 (TDA2020) PEPINA KIT
+ 25V, -25V / + 12V, -12V,
symmetrical amplifier board + LM7812, LM7912"

Only the the transformer is missing.
Guys, another question about the power supply board on sell: what are those four metallic rings near the electrolitic caps?
Thank you 😉
Best regards!🙂

 

[Boydk]

Just DO remember, that it needs a heatsink mounted on the top, before you try out the efficiency of the TDA2020 🙂

 

[Peters8]

Just DO remember, that it needs a heatsink mounted on the top, before you try out the efficiency of the TDA2020 🙂

Thank you Boyd for your precious tip!🙂
Yes, don't worry about that: I've two very robust heat sinks from the 70s.
However, Boyd, could you explain what are those four meatallic rings on the power supply board? (I mean the picture I've posted above).
Thank you very much!😉
Regards

 

[PRR]

....what are those four metallic rings near the electrolitic caps?...

They look like rectifiers; specifically, rectifiers from a automobile alternator. That stud-mount package was used for other power applications, but I never saw it used for a few-Watt chip-amp. Maybe someone had an overstock of car diodes?

 

[anti]

Some Hi-power rectifiers. Meant to be screwed onto a large heatsink.

 

[Peters8]

Take a look at this picture, guys: Here we can see more clearly these strange electronic components on that pcb power supply:
http://pepina.org/snimki/417998.jpg
If someone knows exactly what they're, please let me know!😉

 

[asuslover]

Some Hi-power rectifiers. Meant to be screwed onto a large heatsink.

 

[PRR]

..Here we can see more clearly these strange electronic components on that pcb power supply...

Those are different: they have two tabs on top. They are SCRs.

The ones with a tab and a body are rectifiers, very boring things, and in this case much larger than they need to be for a small amplifier.

There is no "magic sound" here.

Do they work? Use them.

If they don't work, use any standard rectifier bridge. 100V 3A will be plenty for this amp.