freestompboxes.org

Hallo everyone,
I started my amp builder career with ROG Ruby, then Noisy Cricket, then Tube Cricket, then I moved to higher voltage amp IC: TDA 20x0.

I've built a bridge dual supply TDA2050 AMP. Until I supplied with 36V and voltage divider (low current, ±18V) it worked as expected and louder.
Then I moved to transformer ±18V and 6 elna 10mF filter caps and... probably I cooked my ICs.
A bit disappointed, I bought 2 modules from aliexpress, TDA2050 single supply single IC.
Then I tried to modify one from single supply to dual supply. Here the schematic.
The problem is that I find 1.8V on signal line and my + is 18 and my - is -1.8V.
Seems i forgot a resistor from - to GND.
Here pics.

Thanks

In other words.. can someone check last shematics to help me to troubleshoot why I cant achieve ±...V equal in both rails?

Im not using Transformer, Im using 36v and voltage divider (as I did initially with bridge amp) so it should work fine (if I modufied right the module).

Here the culprit module modded.

And here a schematic-module comparison

Please draw a clear schematic that includes everything you're using: PSU, volume pot and all.

I tried to modify one from single supply to dual supply.

Leaving the center tap open, i.e. using it as a unipolar/single supply seems much simpler than what you're trying to do.

I have several of these cheap power amp modules that I bought to play around with. I find it's much easier just buying a single +voltage power supply to use with these amps versus a bipolar supply (stand-alone off-the-shelf bipolar power supplies seem to be few and far between). The disadvantage is that you need the huge capacitor at the output to the speaker, but for low power guitar use it probably isn't a big deal.

Frank_NH wrote: ↑26 May 2023, 13:47 I have several of these cheap power amp modules that I bought to play around with. I find it's much easier just buying a single +voltage power supply to use with these amps versus a bipolar supply (stand-alone off-the-shelf bipolar power supplies seem to be few and far between). The disadvantage is that you need the huge capacitor at the output to the speaker, but for low power guitar use it probably isn't a big deal.

The module is single supply so your advice is no mod. Thanks for nothing.
I'm an expert in electronic DIY. Ive made very complicated layout like Kongpressor.
So my skill is not in doubt.

Probably Ive missed a PCB PATH that cause this.
When I connect 18V to the voltage divider (made by 3 parallel 470K resistors betweeen 3 poles) I measure
+ 9V
0 0V
- -9V
Then they start to change increasing + and decreasing - potential
After some minutes
+ 17V
0 0V
- -1.18V

The schematic are these.
Upper scheme is DUAL SUPPLY
Lower scheme is SINGLE SUPPLY module schematic.
PSU 18V or DRILL BATTERY 18V
Original module scheme Lower
Actual modded scheme Upper (see above)

Gebrey wrote: ↑29 May 2023, 13:43 I'm an expert in electronic DIY. So my skill is not in doubt.

My brother in Christ, you're the one who came asking for help.

The schematic are these.

No they fucking aren't! The volume pot's connection is important for your issue, and so is the PSU.
And it's still not clear why you're trying to adapt it for bipolar supply when you can easily use it as intended.

FiveseveN wrote: ↑29 May 2023, 19:26

Gebrey wrote: ↑29 May 2023, 13:43 I'm an expert in electronic DIY. So my skill is not in doubt.

My brother in Christ, you're the one who came asking for help.

The schematic are these.

No they fucking aren't! The volume pot's connection is important for your issue, and so is the PSU.
And it's still not clear why you're trying to adapt it for bipolar supply when you can easily use it as intended.

Can you please stop helping? And maybe be more clean at talking since we are in a public community?

My achieve is convert it to bipolar.
Since I really checked 10 times everything the only explaination is fried IC.

Frank_NH wrote: ↑26 May 2023, 13:47 I have several of these cheap power amp modules that I bought to play around with. I find it's much easier just buying a single +voltage power supply to use with these amps versus a bipolar supply (stand-alone off-the-shelf bipolar power supplies seem to be few and far between). The disadvantage is that you need the huge capacitor at the output to the speaker, but for low power guitar use it probably isn't a big deal.

These modules are very conservative and the effective power output is subpar. I would like to use bipolar since I have 2 batteries 18V and I want to achieve highest power changing the "parallel to speaker" resistor and cap to lower ohm.

I think my IC is dead.