Need Help Repairing Pyle Guitar Amp after short circuit--only hums & pilot lite

[DrGonz78]

DrGonz78 seems to have more information [that I have a -/+18v power supply] & sees no instability problem.

Look and read this little tidbit... Note the statement on this page "If you have low impedance speakers use +/-18V supply." This was mentioned as way of saying if you running lower than 8 ohms then... do it this way.
http://www.youritronics.com/audio-amplifier-with-tda2050/

It is saying that if you run the chip at max power supply -/+25v supply that it will only be stable with an 8 ohm load. Now typically an amp designed with a 2050 chip the power supply will be run around -/+22vdc. So the power transformer will be a 32vac supply but with a split power supply that will be -/+16vac .

16 * 1.41 = 22.56vdc >>> We multiply the voltage by 1.41 as to figure out the added voltage when the AC is rectified to DC. So most amps I have come across running tda2050 chip will have very similar set up as what I have mentioned.

You can actually confirm your voltage on your amp with the chip disconnected. I would be guessing that the power transformer is 24vac w/ center tap and it results to a split power supply of -/+12vac. 12 * 1.41 = 16.92vdc. Check out your voltages on your amp to be sure.  :dbtu:

Note that when I say that a 2030 chip puts outs only 14 watts that is at 0.5% THD. It will dissipate up to 20 watts but at the expense of increased harmonic distortion. This is with a -/+18vdc power supply.

"Thanks to its high power capability the TDA2050
is able to provide up to 35 W true RMS power into
a 4 ohm load at THD = 0%, V S = ±18 V, f = 1 kHz
and up to 32 W into an 8 ohm load at THD = 10%,
V S = ±22 V, f = 1 kHz."

That is from the data sheet and it even implies that running it at 4 ohm load that you should use -/+18vdc supply. Makes sense to me more each time I think about it. Now confirm your power supply voltages to make sure. Which if a 2030 chip suggests -/+18vdc supply then I would think its very close to that indeed.

[phatt]

+1 what DrGonz said.

It's x2  current at 4 Ohms and that tiny little metal tab has to pass ALL that extra heat across to the heat sink. Not possible :lmao:, the chip would need a larger surface area. Tiss a bit like adding a V8 engine to a mini minor while still relying on the tiny mini minor radiator to dissipate the extra heat. Yes the engine will run and as long as you don't press the pedal it may idle and stay cool but no chance if you crank up the engine on a long drive. :duh :duh

Same for that Chip,, safe at lower supply voltage but not capable of dissipating the extra heat at full supply.

If your next Q is; Why can't I just use a bigger heat sink?
Because the surface area can't pass enough heat to the larger heat sink,, false economy.
The laws of fizzy stuff don't change no matter what the data sheet claims.
Phil.

[Roark]

I would be guessing that the power transformer is 24vac w/ center tap and it results to a split power supply of -/+12vac. 12 * 1.41 = 16.92vdc. Check out your voltages on your amp to be sure.....
Now confirm your power supply voltages to make sure. Which if a 2030 chip suggests -/+18vdc supply then I would think its very close to that indeed.

-------------------------------------------------------------------
The label on the Transformer says:
"TDB-15L-1,   
OUT: 12VX2,     
ACIN: 120V"

Is this the "split power supply of -/+12vac" that DrGonz78 guessed? [so I don't need to measure the Transformer voltage]?
----------------
Many Thanks to DrGonz78, again, for that detailed analysis!!

[g1]

Yes that is the 12V Dr.Gonz meant, I think you should be fine.

I'm not really in agreement with what the seller said anyway, at least not for this application:
"The TDA2050does not begin to taper off power at 18 watts.
So, the power supply may become loaded down trying to feed the chip."
Reading between the lines, he seems to be implying the original 2030 would have been limiting at 18W.  I think in a guitar amp, it would have just been clipping, (not tapering off) so any power supply limitation (causing instability) should have also been evident with the original chip.
In any case, worst case scenario is the chip burns up when pushed to hard into clipping, which is what we would expect happened to the original chip anyway.