You still get 10V DC at the output?
If so, move on. Your problem is somewhere else.
First do a DC measuring and write it on the schematic. Look at the voltage whether it make sense or not.
Then use the scope to look at where the noise comes from starting with the input of the TDA7313, then at the output of the TDA. Find out where the noise starts.Go through the whole signal path and find where it starts.
Do it step by step logically, don't just jump into conclusion so fast. Find the source of problem and talk about it. Don't pull parts out so quick. You might have just pulled out a good regulator already.
BTW, don't border to measure the current drawn, If you have the clean and 10V, you are ok with the regulator.
Hello. Back to this unit, I've closed the cover with the problem "solved" by now.
Following your advice, I've focused to find the source of the noise. It was the TDA7313 causing the noise (the unit has 2 TDA7313, managing "zone1" and "zone2" outputs, and the Zone 2 was silent, just the Zone 1 was noisy. Since it was very intermittent, it was hard to catch it. Many times, with all the test setup connected, it didn't do the noise. Then I discovered that moving the volume up or down could trip the noise, specially when going to zero and keep going down with the "down" button.
What cheated me 1st time was that freezing the regulator, the noise stopped, but I think it was due to limiting the current or the voltage to the TDA. Freezing the TDA also stopped the noise.
What I did:
(after searching for a replacement locally, not available, found just the through hole version, not the smd IC)
The TDA is fed by the 10V regulator and a 15 ohm resistor, which drops around 0.4V (around 27mA at that resistor) The absolute max supply voltage for that IC is 10.2V, and supply voltage is 6 to 10.2V. Since freezing the 10V regulator stops the noise, I decided to drop the supply voltage a bit more to make the IC to run cooler. Replaced the 15 ohm with a 56 ohm resistor, and supply voltage at the IC came down to 8.5V.
Added a heat-sink to the 10V regulator, added a heat-sink to the TDA7313, and it worked silently for about one week, so I think the problem is fixed by now, in the meantime I'll get a replacement IC from the web, or if needed, swap the Zone 1 and Zone 2 chips (zone 2 is not used by the owner), but desoldering and resoldering those 28 pins ICs in that tiny board is not easy without the proper smd reworking tools.
BTW, what I write in 10 lines of text, took me weeks of going to the board, testing, assemble, disassemble, measure here, there, let it warm up, test it for weeks, and so. A couple of weeks ago seemed solved with just the heat -sinks, but putting an ear close to the tweeter, the noise was still there at a very low level.