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TDA2050 / LM 1875 - help!
TDA2050 / LM 1875 - help!
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Old 11th February 2011, 06:43 AM   #1
lukaslukas is offline lukaslukas  Canada
diyAudio Member
Join Date: Mar 2010
Unhappy TDA2050 / LM 1875 - help!

The Story: I recently bought a cheap bass amp from craigslist and for $40 bucks i got a great enclosure...the amp and speaker are just awful so i opened it up to see what could be done.

The amp section is based on a TDA2050 chip with a bunch of TL072 opamps.
I replaced the opamps and the sound was considerably cleaner. But the amplifier was nearly blown so it continued to hiss and buzz. I couldn't get a 2050 chip and had to use a TDA2030 which is more or less a less powerful version of the 2050. After destroying a chip while soldering - i didn't have any needlenose around to take the heat - i got it to work and the was ok. Still hissing, but considerably less!

Here's the problem: i upgraded the power supply caps from 2200uF 35V to 5600uF 50V and the worked for a minute or two but then started to break up and just sent DC to the speaker - i could see the cone stuck in one direction...

Is the poor TDA2030 chip fried or is it the caps? i've read that the exact voltage doesn't matter with caps as long as it's _above_ the minimum voltage supplied. I'm planning to swap the TDA2030 for an LM1875, but i don't want to kill that one too...

Any help appreciated!
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Old 11th February 2011, 04:32 PM   #2
pacificblue is offline pacificblue  Germany
diyAudio Member
Join Date: May 2008
Did you check the polarity of the caps. If they blow, they are usually the wrong way round. It is usually a good idea to connect the amp to the power supply only after making sure the power supply works as intended.

If the caps blew, that does not necessarily mean the IC is fried. The speaker might be however.

Capacitor voltage rating should be above the maximum voltage supplied which was obviously the case.
If you've always done it like that, then it's probably wrong. (Henry Ford)
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Old 11th February 2011, 04:59 PM   #3
lukaslukas is offline lukaslukas  Canada
diyAudio Member
Join Date: Mar 2010
Lightbulb Caps are ok.

If the caps blew, that does not necessarily mean the IC is fried. The speaker might be however.
The caps are ok, i only replaced them to see if they would improve the bass response The original speaker was very crappy and i replaced that as well. The sound is pretty good for a minute or two then the amp starts to crackle and pop, then DC goes to the speaker and i have to turn it off... I'm gonna try a new TDA2030/50 chip and I've ordered a couple of LM1875's... hopefully it was just my bad soldering
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Old 8th January 2012, 06:06 PM   #4
brianhutchins is offline brianhutchins
diyAudio Member
Join Date: Jan 2012
the reason why the tda2030 BLEW was not because of the caps issue, the tda2030 is rated for a max voltage of 18 VOLTS, while the tda2050 is rated for max voltage of 25 VOLTS, NOW, that's 7 VOLTS that the tda2030 couldn't deal with and thus blew the tda2030. when changing out parts, ALWAYS check the DATASHEETS between the two to SEE WHAT THE DIFFERENCES ARE!!!! WHEN IN DOUBT, meause the voltages going to the pins of the IC and SEE what VOLTAGES you have there, usually pins 1 and 3 (CASE). on tda20's, THAT'S THE MIN. VOLTAGE the replacement should have. now, you CAN take a tda2050 and have that take the place of a tda2030 because you DO have 7 volts to play with and you're more than within the specs, you just CAN'T put in a tda2030 where a tda2050 was because you'll over - voltage the chip, causing it to overheat, and ultimately blowing it like you did. i've seen some people blow a nice crater in the middle of tda20's just by doing that.
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