Another Rockford T1500.1bd issue

impactair · 13th January 2012, 02:23 AM

I seem to be getting my behind whipped by another T1500. This amp originally had 1 output fet shorted that I could tell. I replaced the channel and powered up only to blow another fuse. I checked all components on the audio side and everything seems ok. I powered up with a two ohm resistor and something buzzes for a few seconds, and then pulses, it sound like it's coming from the transformer but I am not positive. Also I noticed the power supply fets read around .70 volts between the drain and source on diode check, which seems low but none are defective. I have never heard an amp make these noises so any insight would be appreciated. Also after removing all of the p.s. fet's to check them outside the board, one was shorted. All were replaced.

timwebb · 13th January 2012, 02:32 AM

u checked the drive transistors and gate resistors?

impactair · 13th January 2012, 03:04 AM

Yes

timwebb · 13th January 2012, 03:06 AM

u try twisting on it to see if the voltage change? it could be a short.

bzhei · 13th January 2012, 05:00 AM

whenever i set rockford power series (non-elite) gains on the scope, everytime the signal level clips on the scope using a -10dB 40hz overlap track. i hear the buzzing sound. i've experienced it with all non-elite power series that sometimes even without a scope, you can tell the amplifier just clips @ -10dB 40Hz signal once you hear the buzzing sound. back down a little and the buzzing sound goes away.

maybe the gain pot is messed up?

Perry Babin · 13th January 2012, 06:21 AM

Only connect the remote and the ground (no B+). What is the DC voltage on each of the power supply FET gate legs?

Black probe on amp ground.

impactair · 13th January 2012, 01:56 PM

It is 12v, I forgot to mention that the voltage only drops after the remote is applied

impactair · 13th January 2012, 02:00 PM

I don't have any audio signal going to it, the guy I bought it from told me that it would buzz and put out distorted audio but when I checked it, it just blew fuses. If the gain pot was messed up it still should not cause the fuse to blow right? I thought the sound would just be distorted and, or humming?

bzhei · 13th January 2012, 03:13 PM

perry can shed light on this. i have his dvd and i'm also in the process of learning.

but i tried awhile ago, even the t6004 makes the buzzing sound inside the amp when -10dB 1kHz overlap signal is going through the amp. and with the overlap, the gain pot is set higher than when using 0dB. but yours doesn't have signal input yet it buzzes so it could be different.

brandes.cm · 13th January 2012, 03:37 PM

If you have 12V on the gate leads that would tell me the 3525 or TL494(which ever it uses) is not running. What are the voltages on that part?

13th January 2012, 02:23 AM	#1
impactair diyAudio Member Join Date: Oct 2011	Another Rockford T1500.1bd issue I seem to be getting my behind whipped by another T1500. This amp originally had 1 output fet shorted that I could tell. I replaced the channel and powered up only to blow another fuse. I checked all components on the audio side and everything seems ok. I powered up with a two ohm resistor and something buzzes for a few seconds, and then pulses, it sound like it's coming from the transformer but I am not positive. Also I noticed the power supply fets read around .70 volts between the drain and source on diode check, which seems low but none are defective. I have never heard an amp make these noises so any insight would be appreciated. Also after removing all of the p.s. fet's to check them outside the board, one was shorted. All were replaced.

13th January 2012, 06:21 AM	#6
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Only connect the remote and the ground (no B+). What is the DC voltage on each of the power supply FET gate legs? Black probe on amp ground. __________________ Links >> Basic Car Audio Amp Repair * Basic Car Audio Electronics * New Site * Basic Switching Power Supply Design * Basic Computer Skills << Links

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13th January 2012, 02:32 AM	#2
timwebb diyAudio Member Join Date: Jan 2010 Location: memphis tn	u checked the drive transistors and gate resistors?

13th January 2012, 03:04 AM	#3
impactair diyAudio Member Join Date: Oct 2011	Yes

13th January 2012, 03:06 AM	#4
timwebb diyAudio Member Join Date: Jan 2010 Location: memphis tn	u try twisting on it to see if the voltage change? it could be a short.

13th January 2012, 05:00 AM	#5
bzhei diyAudio Member Join Date: May 2011	whenever i set rockford power series (non-elite) gains on the scope, everytime the signal level clips on the scope using a -10dB 40hz overlap track. i hear the buzzing sound. i've experienced it with all non-elite power series that sometimes even without a scope, you can tell the amplifier just clips @ -10dB 40Hz signal once you hear the buzzing sound. back down a little and the buzzing sound goes away. maybe the gain pot is messed up?

13th January 2012, 01:56 PM	#7
impactair diyAudio Member Join Date: Oct 2011	It is 12v, I forgot to mention that the voltage only drops after the remote is applied

13th January 2012, 02:00 PM	#8
impactair diyAudio Member Join Date: Oct 2011	I don't have any audio signal going to it, the guy I bought it from told me that it would buzz and put out distorted audio but when I checked it, it just blew fuses. If the gain pot was messed up it still should not cause the fuse to blow right? I thought the sound would just be distorted and, or humming?

13th January 2012, 03:13 PM	#9
bzhei diyAudio Member Join Date: May 2011	perry can shed light on this. i have his dvd and i'm also in the process of learning. but i tried awhile ago, even the t6004 makes the buzzing sound inside the amp when -10dB 1kHz overlap signal is going through the amp. and with the overlap, the gain pot is set higher than when using 0dB. but yours doesn't have signal input yet it buzzes so it could be different.

13th January 2012, 03:37 PM	#10
brandes.cm diyAudio Member Join Date: Sep 2009 Location: Wisconsin	If you have 12V on the gate leads that would tell me the 3525 or TL494(which ever it uses) is not running. What are the voltages on that part?