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TDA 2030 Guitar amp build oscillation problem

Started by TK, September 26, 2017, 01:52:55 PM

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TK

Hi I was wondering if anyone can Help with a TDA 2030 audio chip guitar amp oscillation problem that I'm having with my amp build.

I'm using a Single supply and using the Schematic from the Data sheet for single power supply application.

After finally getting the chip to amplify a guitar signal from a tl-072 pre amp, and figuring out where to put the volume control and what size pot to use,, I've managed to get the set up working.. Only problem is,, It oscillates at a particular volume setting.. I'm truly stumped here.. I'm using the components listed on the schematic, but i'm wondering if there is some other component that has not been included? How do I stop this tda 2030 from oscillating? Hope fully some one can help. Thank you...

tonyharker

Can you show us some pictures and the schematic you used?

TK


J M Fahey

I bet the schematic is fine, oscillation problems come from poor layout or shielding, poor grounding, etc.

Jazz P Bass

Have you installed C3/ C9 (0.1 uf) & R4/ R10 (1 ohm)?

TK

Hi J.P.. Hi J.M.. Thank you for your replies,, Yes I have installed C3 (.1uf) and R4 (4.7ohm) .

Here is what I've come up with,,, I uninstalled C8(B?) from the Hi pass filter and reversed The polarity of C1 the input capacitor,,, Guess what?? The Oscillation totally stopped, Yaaaaaaaay,,,,,

I have one more question if I may,,, Do I really need to install the 2000uF capacitor on the output to go into the speaker? Aaaaaaaaaaaaand what happens if it is not installed? I realize that it is there to block the DC from hitting the Voice coil but,,??

phatt

Quote from: TK on September 27, 2017, 10:24:55 PM

I have one more question if I may,,, Do I really need to install the 2000uF capacitor on the output to go into the speaker? Aaaaaaaaaaaaand what happens if it is not installed? I realize that it is there to block the DC from hitting the Voice coil but,,??
YES tiss there to block the DC which will burn out the voice coil,,,, but If you just can't accept the science,, feel free to try it ;)

A cap at that point has the advantage of being a point where you can tailor the freq response a bit,,smaller values will wipe off excess bass if needed.
Phil.

TK

Hi Phil,, How will or does it burn out the voice coil? :)

Jazz P Bass

"How does a dc voltage burn out a voice coil"?

Heat.

g1

Yes, heat.
In this case, the heat is a result of the power going to the speaker.  Voltage squared, divided by the resistance of the voice coil.
Why does the power from DC burn the coil, when AC voltage usually does not?
DC is constant polarity, so the coil sits in place.  The usual heatsinking of the magnet and polepiece when the coil is moving from AC does not take place.
Often the DC is even big enough to push part of the coil out of the gap, and that part will burn first.

J M Fahey

Quote from: g1 on September 29, 2017, 01:37:22 PM
Yes, heat.
In this case, the heat is a result of the power going to the speaker.  Voltage squared, divided by the resistance of the voice coil.
Why does the power from DC burn the coil, when AC voltage usually does not?
DC is constant polarity, so the coil sits in place.  The usual heatsinking of the magnet and polepiece when the coil is moving from AC does not take place.
Often the DC is even big enough to push part of the coil out of the gap, and that part will burn first.


Fresh voice coil on right, burnt on left.
Notice the back area looks almost normal (it stayed inside the gap), but forward one which was pushed out (speaker cone pushed forward by positive DC) is toasted:



same but higher power amplifier involved:


notice burned glue and insulation and wire on its own travelled even forward.

TK

Ah, I get it,, That's crappy for sure... will place the cap in the positive side of the chip output..... Thanks you guys.

Jazz P Bass

Understand that the reason for the capacitor on the output is because the power supply is a single polarity.

Therefore the output will 'sit' at 1/2 of the supply voltage.
Which is Volts dc.

The cap is not needed on a dual supply because the output 'sits' at 0 Vdc.

TK

Very strange indeed. This is my first experience with these chips, so learning an amazing amount about them for sure... I've blown 2 of them up,, which is very frustrating for sure.. Had the last one wired up and everything was correct.. Voltage from the tl-072 was finally working and before I put it in the Chassis it worked,, after that nothing,, Crappy,, LOL,,, No output,, going to try another TDA2030,, Not sure if the issue was static or overheating or just being played with too much,,, Checked the temp with my lazer and it got hot but still under the radar,,, I'll take the dead chip out an install a new one and see what happens,,, Thanks for your Help.. Really super appreciated it for sure..

phatt

Q do you have the 2030 mounted on a heat sink?  If so is it electrically isolated from the heat sink. The tab is not ground so you always check that it's not shorted to chassis before you apply power.
Phil.