amp powers up, puts a very muddy sound out, also red light under glass lights up. Amp was given to me so i know very little about it, but from what i have been told this is a quality piece, so i would like to give it a shot of repairing. Any good ideas on where to start would be great, amp has rust on it so i am assuming it got wet. also have a mtx blue thunder that gets buzzing noise when key turned past acc. , i use other amps on the same wiring set up , with no problems, so thought this one may be a little easier to start with, had it apart and found no visible leg breaks are loose ends. Thanks in advance, Phil
Have you adjusted the crossovers built in for the channels ? Perhaps someone had it setup for bass usage this would explain the muddy sound easily. Try adjust the selector switch for each set of inputs to bypass the crossovers.
As for the leds there are two for each channel on the main board and that means you should see 8 total if all the channels are still working properly.
The rust is common for this amp if it has been exposed to moisture, the Titanium coating is prone to having rust develop underneath and on the edges and from there on its all down hill for the finish. PG does not have any replacements any longer nor do they refinish amps like they use to many years ago.
Oh any noise you may get from the amp try moving the RCAs at least 4 inches away from the power wires. These like Macintosh amps are prone to induced noise into the RCAs via magnetic field coupling effects of having the RCAs too close to the power wires feeding the amp. Had this problem myself many years ago...live and learn eh?
As for the leds there are two for each channel on the main board and that means you should see 8 total if all the channels are still working properly.
The rust is common for this amp if it has been exposed to moisture, the Titanium coating is prone to having rust develop underneath and on the edges and from there on its all down hill for the finish. PG does not have any replacements any longer nor do they refinish amps like they use to many years ago.
Oh any noise you may get from the amp try moving the RCAs at least 4 inches away from the power wires. These like Macintosh amps are prone to induced noise into the RCAs via magnetic field coupling effects of having the RCAs too close to the power wires feeding the amp. Had this problem myself many years ago...live and learn eh?
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mtx
i'm pretty sure its an internal issue with the mtx as well as the PG. The PG is in overload protection mode upon being turned on, and the mtx has noise and the rca's are on the opposite side of the car all the way to the amp in the trunk, i have another mtx amp running on the same wiring currently with no noise issue. By the way the mtx amp is a blue thunder 752, bought it off ebay and had noise from the start, the rca plugs are loose coming out of the amp, but the connection is good, is it possible the noise is caused by a bad rca plug?
i'm pretty sure its an internal issue with the mtx as well as the PG. The PG is in overload protection mode upon being turned on, and the mtx has noise and the rca's are on the opposite side of the car all the way to the amp in the trunk, i have another mtx amp running on the same wiring currently with no noise issue. By the way the mtx amp is a blue thunder 752, bought it off ebay and had noise from the start, the rca plugs are loose coming out of the amp, but the connection is good, is it possible the noise is caused by a bad rca plug?
Well the protection circuitry usually does not lie about this amps condition, so I would best say you have at least one damaged channel. The last one I repaired had a blown transistor in the VI limiter stage which caused this condition to occur.
Could you please read the DC voltage present on each speaker terminal pairs and let me know what that reading is. The most likely culprit will be the channel with high DC output across the speaker terminals. By high I mean 30 milli-volts DC or higher reading, possibly drifting with heat.
PG used the same design in most of their gear and the common areas of this sort of thing to happen are located around the red leds in each channel. The other big failures will be the outputs and drivers possibly. But these are the common failures i am describing.
Also please check all the green bodied resistors as these are fuse safety resistors and they open up just like fuses to protect the amp in case someone gets too zealous driving the amp into the neither regions of reality. Several of these are located under the flat panels of the heatsink, and to reach them the amp must be completely disassembled to access them for inspection. If you do this you will need some heatsink compound to reassembly the amp properly afterwards.
The most likely channel to be damaged are the rear channels as lots of folks like to run these in Sub mode and try driving a three channel system. this usually kills one or both of these channels due to excessive over drive and heat build up since these channels have the smallest sink surface area to begin with.
If it sounds like i have seen a few of these well I have and these are the common things I have dealt with.
As for noisy RCAs lift the crossover board off its standoffs and inspect just behind the RCA connectors looking for two beige 1/8 watt carbon comp resistors. They may be burnt black and beyond recognition. They are 100 ohm and they are the RCA ground fault protection, and they burn up and open when excessive current passes through the RCA ground shield. Again this is a common issue when these amps are abused badly.
Without some voltmeter readings inside this amp this is the best info I can give without seeing the amp first hand on my bench...
thank u
i will see if i have some time to check some of that stuff later today, watchin my 2 year old son right now, and he thinks he needs to help me with everything, and the last time i attempted to install some components in the rear deck he climbed in my car and tried putting his hand thru the cone on the driver. But again, thank u for a starting point, i will most likely just try to fix the mtx myself, and if i have any luck, then i may try the PG, but i took the cover off, and got a little scared when i seen the boards mounted on top of each other.
i will see if i have some time to check some of that stuff later today, watchin my 2 year old son right now, and he thinks he needs to help me with everything, and the last time i attempted to install some components in the rear deck he climbed in my car and tried putting his hand thru the cone on the driver. But again, thank u for a starting point, i will most likely just try to fix the mtx myself, and if i have any luck, then i may try the PG, but i took the cover off, and got a little scared when i seen the boards mounted on top of each other.
Don't let the stacked board worry you. The ribbon cables are very durable. Just fold the board toward yourself and let it lie on the table in front of you. You can remove the led panel board on top so the leds won't get broken off and return it later on. The amp does not need this cosmetic item to work properly.
This board is the input / crossover filter board, and it outputs thru the ribbon cables connects to the final buffer stage op-amps I.E. the NE5532's located on the main board. Just after these are the four main amp channels all side by side and somewhat packed together. From left to right are fronts on left and rears on the right.
And yes I am pulling all this from memory this morning, must be some good coffee today, eh? I also have set of spare boards sitting here under my bench, just in case I get lost...
This board is the input / crossover filter board, and it outputs thru the ribbon cables connects to the final buffer stage op-amps I.E. the NE5532's located on the main board. Just after these are the four main amp channels all side by side and somewhat packed together. From left to right are fronts on left and rears on the right.
And yes I am pulling all this from memory this morning, must be some good coffee today, eh?
I also have set of spare boards sitting here under my bench, just in case I get lost...- Status
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