Both of these amps are 2002 models which are old but definitely not "old school". I purchased them new years ago and ended up blowing both. They have collected dust for quite some time.
I just wanted opinions as to whether or not these are worth the time and effort to repair? The problem may just be in the thermal overload protection? They were not catastrophic failures, as the internals "look" fine and did not pop the in-line fuses if i remember correctly.
I just wanted opinions as to whether or not these are worth the time and effort to repair? The problem may just be in the thermal overload protection? They were not catastrophic failures, as the internals "look" fine and did not pop the in-line fuses if i remember correctly.
Thermal overloads reset themselves. Your amps are damaged most likely. I can't attest to value of repairing your amps. Its generally something you either want to do, or not.
If there are no visibly damaged components it likely means the protection circuitry shut down the amp before any smoke letting occurred. This means you will have to meter out components till you find the issues and correct them. try ohming out the power devices attached to the heat sink. Generally speaking they tend to short out when they fail...hope this helps some.😉
If there are no visibly damaged components it likely means the protection circuitry shut down the amp before any smoke letting occurred. This means you will have to meter out components till you find the issues and correct them. try ohming out the power devices attached to the heat sink. Generally speaking they tend to short out when they fail...hope this helps some.😉
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Thanks for the reply! I'll start checking for shorts and see what i find. If the repair appears to be fairly simple, I may make my first amp repair(s)! I have missed having a good sounding system...
I decided to take a better look at the 150 and removed the boards for a closer look. I found heat discoloration around 2 resistors at the bottom right of the board.
The resistors are in-line with fets IRF540 and IRF9540 (which appear to be on the same channel) and test at 0.3 Ohms and are not passing voltage through on diode tests. I don't know anything about color codes so I have no idea where to begin.
I get a whopping 28.7 ohms on the "bad" 9540 and several thousand on the other. All other pairs seem to have nearly identical readings (with each other).
I am a complete novice so I don't know if I'm testing correctly.
Any ideas?
The resistors are in-line with fets IRF540 and IRF9540 (which appear to be on the same channel) and test at 0.3 Ohms and are not passing voltage through on diode tests. I don't know anything about color codes so I have no idea where to begin.
I get a whopping 28.7 ohms on the "bad" 9540 and several thousand on the other. All other pairs seem to have nearly identical readings (with each other).
I am a complete novice so I don't know if I'm testing correctly.
Any ideas?
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Try Perry Babin's Tutorial links first:
Links >> Basic Car Audio Amp Repair * Basic Car Audio Electronics * New Site * Basic Switching Power Supply Design * Basic Computer Skills << Links
Your channels outputs are blown, and the darkened resistor is burnt. It connects to the shorted output. This is a MESHA board amp try the links above Perry has done all the work for you and put it all together in a easy read. You will need more then a simple hand held soldering iron to remove and replace those fets attached to the MESHA panel. There are several methods. Its just large scale SMD mounting, but it will require a large heat source to remove those safely and not damage the panel so it can be reused. RF used to sell the panels but that was a long time ago. You will likely need to repair the existing panel. I use a Hakko hot air reflow wand, others use mini torches. It will be a learning experience if your a novice like you say you are. Perhaps you might defer this repair to someone that has done it before, since you lack the tools and experience to do it. DO NOT tear the device off the panel. It will simply slid off once you have it heated enough. Careful at these temperatures a severe burn is very possibly...hence my reasoning that you might have an experienced tech repair this one.
PS oh and yes I have at least a couple dozen of these over the years. Your likely going to have damaged components further back on the board in that channel. The schematic is available from RF at this link: http://194.204.29.93/rockford/techlib/products.html
Links >> Basic Car Audio Amp Repair * Basic Car Audio Electronics * New Site * Basic Switching Power Supply Design * Basic Computer Skills << Links
Your channels outputs are blown, and the darkened resistor is burnt. It connects to the shorted output. This is a MESHA board amp try the links above Perry has done all the work for you and put it all together in a easy read. You will need more then a simple hand held soldering iron to remove and replace those fets attached to the MESHA panel. There are several methods. Its just large scale SMD mounting, but it will require a large heat source to remove those safely and not damage the panel so it can be reused. RF used to sell the panels but that was a long time ago. You will likely need to repair the existing panel. I use a Hakko hot air reflow wand, others use mini torches. It will be a learning experience if your a novice like you say you are. Perhaps you might defer this repair to someone that has done it before, since you lack the tools and experience to do it. DO NOT tear the device off the panel. It will simply slid off once you have it heated enough. Careful at these temperatures a severe burn is very possibly...hence my reasoning that you might have an experienced tech repair this one.
PS oh and yes I have at least a couple dozen of these over the years. Your likely going to have damaged components further back on the board in that channel. The schematic is available from RF at this link: http://194.204.29.93/rockford/techlib/products.html
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The output transistors were the only defective parts I could find in the 150. I ordered and replaced what I could find and (after sorting through my awful soldering job) the amp simply works. I didn't even replace the burnt resistor because I wasn't sure what wattage/size etc I should replace it with.
I tested each channel independently and then bridged and the amp barely gets warm after 20 to 30 minutes of running bass music. I even went so far as to run a signal generator at 40-45 Hz for a while.
If I remember correctly, I blew this amp while running it bridged into a 2 ohm load (far from recommended for this amp).
It seems like it was too easy to me. Could I be this lucky? I guess I'll move on to the 550 and hope for the same result...
I tested each channel independently and then bridged and the amp barely gets warm after 20 to 30 minutes of running bass music. I even went so far as to run a signal generator at 40-45 Hz for a while.
If I remember correctly, I blew this amp while running it bridged into a 2 ohm load (far from recommended for this amp).
It seems like it was too easy to me. Could I be this lucky? I guess I'll move on to the 550 and hope for the same result...
I'm not going to be so lucky with the 550 it seems. It trips my power supply with just a REM connection. A quick resistance check makes it appear as if all but one transistor in the right channel is blown. I may wait until I get better equipment before I tackle this one!
It's likely that only 2 of the output transistors are shorted. Measure from leg 1 to leg 2 for all of the outputs that appear shorted. It's likely that one of each part number (540/9540) will read lower than the other 4. Remove those from the circuit and re-check the remaining FETs.
You are correct as always! ! One each of the 540/9540 are showing ~2 ohm resistance.
What concerned me was the roughly 20 resistances on the others in the area. I assume I am getting these readings because of the failed resistors still in the circuit?
Thanks Perry!
What concerned me was the roughly 20 resistances on the others in the area. I assume I am getting these readings because of the failed resistors still in the circuit?
Thanks Perry!
~1 and ~2 ohm on the bad 540/9540. The rest of them look normal now.
I have spares I ordered for the 150 repair but only one 540 and two 9540. I thought I read transistors should be matched?
I have spares I ordered for the 150 repair but only one 540 and two 9540. I thought I read transistors should be matched?
You can clamp everything down (leaving the empty locations open) and power it up through a small fuse or a current limiter to see if there are any other problems.
Before doing that I found resistor 271 reading ~75 ohms. It' severely discolored but look as if it is supposed to be a 0.1 ohm %5 like the rest of them on the board.
This is where I got lost on the 150. I do not know how to calculate the wattage I need? I look at the schematic and I see RM2-001 .1 and assume that designates the wattage?
This is where I got lost on the 150. I do not know how to calculate the wattage I need? I look at the schematic and I see RM2-001 .1 and assume that designates the wattage?
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