Planet audio tt1250 works but have a high pitch noise on the speaker

ivkata · 16th December 2011, 11:51 PM

Ok got this amp on ebay, was sold to me as broken . the amp power on fine and dosent aper to ever been repaired . Audio is clear however there is a high pitch noise ( like jet engine noise ) that starts 1-2 seconds after the amp is powered. Noise is presented with or without rya connected ,with or without audio so i believe to be internal .this units have internal fan can the fan be the reason for the parasite noise

ivkata · 12:32 AM

and 1 min later no audio no noise now ,wtf

Opened the amp and tested the output rails I'm getting + - 54 volts witch i believe is more than enough . tested most of the op amps and they are fine , however IC111 appears to be getting -+ 54 volts as well and this is over the parts specs -KIA393P .will remove it from the board as defective by now and see why I'm getting that much power to it when the other one is getting +- 9

Perry Babin · 17th December 2011, 10:50 PM

You are not seeing ±54 volts on it. It's sitting on the negative rail (pin 4 connected to the negative rail) and pin 8 is 12v above the negative rail. I think you'll find only 12v if you place the probes directly on the two power supply pins for the IC.

ivkata · 17th December 2011, 11:33 PM

thanks perry i saw that as well ,my issue is that i was getting 54 v on all other legs of the op amp ,so its either my multimeter going crazy or its me . i don't have any kia393p ic i do have 4558d can i swap them out

16th December 2011, 11:51 PM	#1
ivkata diyAudio Member Join Date: Dec 2010	Planet audio tt1250 works but have a high pitch noise on the speaker Ok got this amp on ebay, was sold to me as broken . the amp power on fine and dosent aper to ever been repaired . Audio is clear however there is a high pitch noise ( like jet engine noise ) that starts 1-2 seconds after the amp is powered. Noise is presented with or without rya connected ,with or without audio so i believe to be internal .this units have internal fan can the fan be the reason for the parasite noise

17th December 2011, 12:02 AM	#2
ivkata diyAudio Member Join Date: Dec 2010	and 1 min later no audio no noise now ,wtf Opened the amp and tested the output rails I'm getting + - 54 volts witch i believe is more than enough . tested most of the op amps and they are fine , however IC111 appears to be getting -+ 54 volts as well and this is over the parts specs -KIA393P .will remove it from the board as defective by now and see why I'm getting that much power to it when the other one is getting +- 9 Last edited by ivkata; 17th December 2011 at 12:32 AM.

17th December 2011, 10:50 PM	#3
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	You are not seeing ±54 volts on it. It's sitting on the negative rail (pin 4 connected to the negative rail) and pin 8 is 12v above the negative rail. I think you'll find only 12v if you place the probes directly on the two power supply pins for the IC. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

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17th December 2011, 11:33 PM	#4
ivkata diyAudio Member Join Date: Dec 2010	thanks perry i saw that as well ,my issue is that i was getting 54 v on all other legs of the op amp ,so its either my multimeter going crazy or its me . i don't have any kia393p ic i do have 4558d can i swap them out

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