This amp seems to be a bit of a stumper for me. I read the section on BD1500 on the DVD and am still a little confused as to what is going on with this amp.
It powers and is stable on the bench out of the sync. Rail voltage seems to be a bit confusing; either that or secondary ground has floated well beyond what I normally see, although now as I type this up I believe this amp really only produces positive rail voltate. Referencing amp's general ground, I see 112vDC at the rail and 56vDC on RCA shields. If i reference R44 which I believe is CT I see +57vDC and -55vDC at the rails, but I also see -55vDC on RCA shields.
Referecing RCA shields, I measure expected voltages on the opAmps except for U4, which may be dragging the regulated voltage down to +9vDC and -10vDC. To be more clear, the other three opamps are seeing +-13.5vDC on the power pins. U4 is showing ~0 volts on remaining pins except pin 1, which has -.65vDC on it. Both sets of LM3x7 regulators seems to be running hotter than expected.
There appears to be somewhat decent audio waves on several of the opamp pins but the audio path may not be reaching the outputs.
It powers and is stable on the bench out of the sync. Rail voltage seems to be a bit confusing; either that or secondary ground has floated well beyond what I normally see, although now as I type this up I believe this amp really only produces positive rail voltate. Referencing amp's general ground, I see 112vDC at the rail and 56vDC on RCA shields. If i reference R44 which I believe is CT I see +57vDC and -55vDC at the rails, but I also see -55vDC on RCA shields.
Referecing RCA shields, I measure expected voltages on the opAmps except for U4, which may be dragging the regulated voltage down to +9vDC and -10vDC. To be more clear, the other three opamps are seeing +-13.5vDC on the power pins. U4 is showing ~0 volts on remaining pins except pin 1, which has -.65vDC on it. Both sets of LM3x7 regulators seems to be running hotter than expected.
There appears to be somewhat decent audio waves on several of the opamp pins but the audio path may not be reaching the outputs.
Woow you are awsome at this stuff. Out of thousands of pins and test points all you needed was less than 20 check points.
Yes, this amp has been coming on with the protection LED lit. I didnt catch that in the first post because the amp seemed to be powering correctly.
I'm at work and will have to swap U21 tonight - I think its a TL072D if I recall and I have new parts.
Yes, this amp has been coming on with the protection LED lit. I didnt catch that in the first post because the amp seemed to be powering correctly.
I'm at work and will have to swap U21 tonight - I think its a TL072D if I recall and I have new parts.
This is a very common failure. If you would have posted that it was in protection mode, it would have been the first suggestion. This is on the following page of the DVD with variations on the way it fails and what to look for:
repair_tutorial/miscellaneousstuff/rockford/repairnotesrockford.htm
repair_tutorial/miscellaneousstuff/rockford/repairnotesrockford.htm
I replaced U21 with a new TL072C opamp and was able to get the amp to power and play some tones. The output sounds very distorted, almost like a Class-AB amp with a failing driver transistor. The scope shows somewhat of a decently clean waveform but something might still be a problem for this amp.
Seankane, I think you may be on to something. Now that I'm able to get some audio pumping through this amp I was able to run more effectively through the DVD troubleshooting and o-scope images.
On this amp there are two MIC4420CTs. U6 seems to be measuring fine: pin 1 on the scope is exactly like what is on the CD. The other MIC4420CT is U10. When I touch the scope to pin 1 of this 4420 the reading appears to be very unclear; and my test speaker attached to the terminals screaches bloody murder while my probe is, again; only touching Pin 1. U10 runs a lot hotter than U6 also.
Here is a shot of the waveform at the speaker terminals with a test speaker attached. This is a ~20v waveform (5v/Div) of a ~100hz sine wave:
Here is pin 1 of U6, a MIC4420CT:
Here is pin 1 of U10, another MIC4420CT:
On this amp there are two MIC4420CTs. U6 seems to be measuring fine: pin 1 on the scope is exactly like what is on the CD. The other MIC4420CT is U10. When I touch the scope to pin 1 of this 4420 the reading appears to be very unclear; and my test speaker attached to the terminals screaches bloody murder while my probe is, again; only touching Pin 1. U10 runs a lot hotter than U6 also.
Here is a shot of the waveform at the speaker terminals with a test speaker attached. This is a ~20v waveform (5v/Div) of a ~100hz sine wave:
Here is pin 1 of U6, a MIC4420CT:
Here is pin 1 of U10, another MIC4420CT:
this is a end of link but what is the start?
it is'nt www.diyaudio.com and it isn't Basic Car Audio Electronics
because i have a Power 551S and i would repair it
i bought this one and after 30min of utlisation no sound! and 40v on right output! i open the amplifier and i saw it has been ever repared regulator and transisotr had been changed! the 3 IRF540 are shorted so i decided to replaced 3 irf540 but after 30min they burn and i have 40v in the right output !
i have read BCAE on amplifier problem but my english is limited, i'm french !
Perry could you help me please?
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