"click"....hum...."click"....louder hum....repeat

[Jazz P Bass]

So here is the beast.



It's a 30 watt Lf, 15 watt Hf 'studio' monitor.

The TDA2052 expects a +25/ -25Vdc power supply to achieve 30 watts.

TDA2052.pdf

[daz]

the 1000uf caps are 35v, yes. But i already put the chip back in so i can't measure at the pads, and it's been in and out several times and i lost a couple pads and had to wire them to their destinations so i really don't wanna pull it again.

[daz]

Edit: Jazz makes a good point. Is there a plus and minus 42V?

Not sure what you mean....theres is of course + and -coming out of the 2 sides of the rectifier? Sorry, i'm dumb i know but i don't understand beyond what i just said.

[daz]

The TDA2052 expects a +25/ -25Vdc power supply to achieve 30 watts.

[ATTACH]33862[/ATTACH]

For the record, i already have that pinout. Been using it from the start.

[g1]

Why on earth would you put the chip back in?
The fault could kill your new chip, and it limits your ability to troubleshoot.
Do not connect the LF speaker as it is also in danger.

[daz]

Why on earth would you put the chip back in?
The fault could kill your new chip, and it limits your ability to troubleshoot.
Do not connect the LF speaker as it is also in danger.

I was using it to determine i anything I did was the fix. If it were just a bad solder joint fr example. With the chip in i can hear if the hum is still there.

[g1]

With the speaker disconnected is there DC on the output leads from the amp?

[Jazz P Bass]

Not sure what you mean....theres is of course + and -coming out of the 2 sides of the rectifier? Sorry, i'm dumb i know but i don't understand beyond what i just said.

The attached schematic shows a 'dual voltage' power supply.
http://music-electronics-forum.com/a...wer-supply.pdf
With your meter black lead on the Ground connection, with the Red meter lead you will read a + voltage at point '+VDC'.
And a - voltage at point '-VDC'.

We still do not have a definitive answer on exactly what these two power rails measure at.
Hint: +25Vdc & -25Vdc would be ideal.

After this fact is established, you can then measure the ripple voltage on the same two points. (with your meter set to read Volts AC).

[daz]

With the speaker disconnected is there DC on the output leads from the amp?

Yes, 23VDC ! So what component would I be most suspect of?

[daz]

Yes, thats what i was saying, theres + and - voltage but if you look at my reply i think g1 missed the - sign because i missed putting a space between the - and the word coming when he referenced your post about that. But that's why i didn't get what you were saying because i had already said there was positive and negative Voltage, i just shouldn't have used the + and - signs and i measured it across the rectifier. But he voltage measured from ground to each is 20VDC. The HF supply is 24VDC for both pos and neg.

The attached schematic shows a 'dual voltage' power supply.
http://music-electronics-forum.com/a...wer-supply.pdf
With your meter black lead on the Ground connection, with the Red meter lead you will read a + voltage at point '+VDC'.
And a - voltage at point '-VDC'.

We still do not have a definitive answer on exactly what these two power rails measure at.
Hint: +25Vdc & -25Vdc would be ideal.

After this fact is established, you can then measure the ripple voltage on the same two points. (with your meter set to read Volts AC).

[g1]

For starters, don't connect the speaker anymore until the DC at the output is gone. It will cook the speaker. You don't need to listen for hum, when the DC is gone the hum will be gone.

The voltage I was asking about was when the chip was removed. You said it was 42volts. That did not seem right so the question was whether there was plus and minus 42V when the chip was out.
Anyway, it was probably a measurement or communication error.
Something is causing the chip to put out DC. Check the DC voltage on pins 5,6, and 7 of the chip. The pin out is shown on the pdf in post #31.

[daz]

Ok, heres something i forgot to mention or maybe just didn't realize it the first time i checked. But the voltage at the speaker outs makes the meter bounce repeatedly back and fourth between positive and negative 20 volts or thereabouts. And now when i tried to measure pins 6 and 7 it bounces all over the place and i can't get any reading on any of them other than they seem to be staying around 1 or 2 volts. 5 reads nothing, just zero.

For starters, don't connect the speaker anymore until the DC at the output is gone. It will cook the speaker. You don't need to listen for hum, when the DC is gone the hum will be gone.

The voltage I was asking about was when the chip was removed. You said it was 42volts. That did not seem right so the question was whether there was plus and minus 42V when the chip was out.
Anyway, it was probably a measurement or communication error.
Something is causing the chip to put out DC. Check the DC voltage on pins 5,6, and 7 of the chip. The pin out is shown on the pdf in post #31.

[g1]

Well, whatever is the source of that DC bouncing on the inputs is your problem.
You have the good HF amp to compare to. I'm pretty sure you will find those voltages stable on the HF chip, at approx. 0volts on the inputs.

[daz]

Well, whatever is the source of that DC bouncing on the inputs is your problem.
You have the good HF amp to compare to. I'm pretty sure you will find those voltages stable on the HF chip, at approx. 0volts on the inputs.

The problem is i have literally checked every component on this thing and probably swapped out every cap on the board ! I just cannot figure out what else it could be. The biggest problem i have tho is that schematic. I'm pretty sure if i could read it i'd have fixed it long ago even with my minimal knowledge. I rarely have this much problem when i have a schematic.

[J M Fahey]

That crappy schematic is absolutely unreadable.

That said, since you seem to have a problem with a TDA2052, which seems to be AC coupled (is there a cap in series with the input?) , I'd just concentrate on it and strictly follow the datasheet example.

So KRK will get angry because you don't respect their "creation"?

F*ck off KRK !!!!! , they should provide a readable schematic to begin with!!!!!.

So think you have a cheap EBay generic TDA2052 powered "1000W PMPO" board before you, and make it work following the factory datasheet, using its suggested values.

Won't even comment what I do in such cases.