Internal crossover blow

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I have a Crystal Pyramid PB481X 2 channel mosfet amp when I got the amp the low filter worked. I have no idea what happened for the low crossover to blow I think it was because it overheated everything else works on the amp except for the low crossover. This has happened before but I don't want to send it in again because the shipping is too much. I would like to know if there is a cheap way to fix this Thanks for the help.
the crossover shouldn't just blow out due to stress, since it isn't stressed or hadles any power. I would check the contacts of the full/HPF/LPF switch, and also check the crossover frequency pot. Also pull the board and check the solder connectiosn, especially around the switches and pots, and large components.
OK I have checked the switches, everything internal I will check tomorrow because I dont want my dad to know. I would also like to know how to check the crossover frequency pot. I don't really know anything internal so please show a picture if possible and I think it is hard to get the switch because the low crossover is in the middle don't think it is the problem because it does switch over. OH! is it normal when I am switching for the voltage to spike down? it doesn't seem good:bigeyes:
that transformer looks fine. the black stuff in the middle ("filling of the donut") is most likely some kind of glue to keep the wires from buzzing about. Generally, if the amplifier can amke some noises and light up, the power supply is fine.

BTW, that amp looks like a cheap Wal-Mart or FLea Market special, so there's no point in spending much money ti fix it. But it would be good to be able to cheaply fix it, or even just for the learning experience.
Ok the pics are blurry because my camera has gon crazy and started giving me 2054x1728 for some reason if u let windows resize it, it should look normal. I have checked the chips and etc. they all seem fine no cracks nothing is black nothing that I can see that looks burnt other than that coil. I don't want my dad to know because he will want to send it back for another one and that will take over 2-3 weeks + charges I personally don't wanna go through that. The coil's wires are darkened to me im sure copper wire is not dark there are some that still look like regular copper. OK the amp was a cheap amp I bought it for $50 from an online store I want to fix it if it is a cheap fix if not than I can live without the low crossover until I buy a replacement or upgrade. Now the pictures thing I'll try to fix just try to work with the pictures maybe editing them yourself may help too.
does the amp otherwise work fine? like does at least one channel work? does it light up? pop fuses? does it pass sound in either full or high pass modes?

when a car amp breaks, in 99% of the cases it's:
1. blown up power supply (the MOSFETS go) - amp will usually blow the fuse even when the remote is off
2. blown up output stage (one channel ether doesn;t work, or the amp gpoes into protect w/o a speaker/signal, or blown the fuse, but only after you switch it on
3. broken connectors/controls or bad solders or cracked board. This will give you all kinds of weird problems

DO you have a multimeter/voltmeter? Evena really cheap one will be good enough for some basic tests

Annother thing I suggest you do would be to take out the whole circuit board (carefully) and look at the bottom and look for any cracked solder joints or broken parts of the circuit board. the cracks can be very subtle. Remember, most cheaper amps (I don't find any issues with a single side board) only have the circuit traces on the bottom of the amp board, and the lines on top are just painted on for looks. Be careful with the board when it's out, and don't power it up while the transistors are not attatched to the heatsink.
OK the problem is only on the low pass filter, both channels work I am using the amp in full mode right now and it is fine the high pass filter also works when i am in the low pass it plays but it is distorted. everything powers up and the power LED comes on the protect LED is not lit I will check for the cracks and I do have 2 volt meter I am still trying to figure out hoe to use the expensive one the cheap one i cant find, but that one I do know how to use I will have to find it... in the meantime can u tell me wut I need to test. I have been looking at pictures of the inside of amps on the forum and I have seen that the coil (that I showed in the picture) is darkened and all the others are still copper colored I think that is the problem because it is the lowpass filter like a passive crossover a coil filters the bass? not sure about crossovers in amps that why im here
ok, if the amp plays o full range, this means that....
1. the power supply works (including that round donut transoformer)
2. both power amplifiers work
3. the input jacks are good
4. the gain/volume contrl is OK
5. at least part of the preamp circuitry is OK

the parts that are OK do not need to be messed with since the amp playing in FullRange proves that they are working.

The means that ONLY culprit must live in the preamp circuitry. Now, the preamp is almostcompletely composed of op-amps (chips). These very rarely blow out, they might b able to be blown out by shorting something to the RCA inpouts, but the low pass circuitry isn't directly connected to the inputs anyways. It is very very rare that you simply fried out an op-amp chip or anything else in the preamp. Strange things can and will happen, but when you trouble shoot a circuit, you first start with the most common failures before tracking down the more obscure failure modes. Also, bad solder connections, etc. don't have you buying replacement components :)

I said that the three most comon car amp failured are:
1. blown PSU (it's usually the MOSFETs, sometimes *explosively*), typified by amp that doesn't turn on, blows fuses
2. blown amplifier outputs (usually blown output transistors, if you're unlucky, they'll also blow some of the other transistors thatconnect to them), typified by amp that blows fuses, goes into protect all the time, and/or has one channel that works, annother dead one
3. broken connectors/controls/solders

by having the amp play usic when in full range, you know that it can't be 1 or 2, and that it must be either a blown up preamp, or a broken control or solder (much much more common). I would check for a busted solder in the vicintity of the preamp circuitry (the crap surrounding the chips and input jacks/controls) and a bad crossover switch. If you have a siwtch or dial to set the crossover frequency, I'd also check it (if the high pass mode works, this control might be just fine). You're looking for circuitry that is *ONLY* used for the low pass mode. circuitry that is used for all modes must be good since full range works.

The high pass/ full range/low pass switch might be bad. I would do two things. First, I would have the amp on playing music (first in low pass, and then in full mode), and jiggle/fanagle all of the inputs and controls, and all of the parts. also push on parts of the board. Does ehacking it do anything? any part that does anything is suspect. Then I would remove the board and pay particular attention to the quality of the soldering on the preamp circuitry and chips, and reflow (and sometimes add a touch of solder, sometimes boards are made with very little solder on cheap thing PCB material and are very very prone to bad solder joints). Remember, a car amp is subjected to much more vibrations in a car (esp if you bolt it to the sub) than home electronics, and any weakness in the physical contruction is going to cause a failure eventually. If the actual crossover mode switch is broken, I'd just take the lazy way out and permanently solder it in the low pass selection (by putting aglob of solder over the pins that are connected when in low pass). guaranteed to fix the switch, but you need to take it apart to change the mode...

What are the symptoms of the amplifier when it's in low pass mode? and areboth channels affected or just one?

WHen I have to repair something, I break down the piece of equpment into different blocks (like breaking down a car into engine/transmissions/tires and then thinking what part can be making it mess up? or breaking up a "car stereo" into a headunit, battery, alternator, speakers, amplifier, sub, and wires) and thinking about the symptoms and which block the failure must be in. It's called the "divide and conquer" method of troubleshooting.

PS. if you can't fixit and need to get anewamplifier, My friend has had good experiences with a $60 DUAL amp (says "340 watt") at Best Buy that puts out a decent 90 real watts per channel (2 channel bridgeable), and a Jensen for $100 (says "720 watts") that's a 4 channel bridgeable units which is essentially two of the DUAL units in one chassis. These aren't world class amps, but they are an awsome vlaue for the money (MTX also gives you great value for the monney, but they're better amps for more money) and are a step above your amp in quality for not much more moeny. I've heard bad things about SONY XPLODs for reliability, but I've never actually used one....
Did you read my last post?

In my last post I do have some the questions that you asked me. When in low pass both channels do work but the they are distorting badly the lowpass filter does work so that means the switch works I have pictures for u under this if it helps could u explain or circle it in the picture and post it remember im not to smart about the insides of an amp i believe the problem is in the preamp area and the lowpass because the high pass does work give me some time for the jingling of components as I need to plug everything back in first. I also thnk that it is one of the "op-amp" chips are blown because the lowpass worked before I don't have the amp siting on top of the subwoofer. if the lowpass worked when I got it wouldn't that rule out solder problems and switch problems? last if u have checked the specs on the amp it is a 600 watt 2 channel amp and my subwoofers are 300 watts each so both amps your friend said won't work for me because the 320 is too low on 2 channels and too high when bridged and the 740 is too high already.
I can't really think of any precautions to keep it from happening again -these things just happen sometimes, especially in the cheaper amplifiers. The car is a pretty rough environment for any piece of electronics to be in (did you ever see how tough the "important" pieces of car electronics are built, like the airbag computer and engine controller?).

I can't really think of anything to keep it from happening again, other than keep stuff in your trunk from hitting the amp, making sure it can't bounce around your trunk, and not bolting it straight to the sub box.

Op-amps can die, but it's pretty rare since they don't handle much power. The amp's power supply and output stages are vulnerable since they push all the power into the speakers. The op-amps in the preamp just control the power delivery, and don't do any heavey lifting for themselves.

I personally don't have much faith in the wattages written on car amplifiers. I typically divide the wattages on the amp by two to get the "eal" wattages. I also pay absolutely no attention to "MAX" watts. The only watts that are good are RMS watts. My friend's getting about 150 watts from his Dual amp. And the other one is essentially two of those Dual amps in one box. I'm not advocating these amps, but I'm saying that sometime the local stores have good deals when they have special deals and sales. Dual and Jensen don't make great amps, but their RMS numbers aren't totally made up. Some of the cheaper brands like Pyramind will simply lie out of their ***** to sell a "1000 watts" amplifier. I think your amp is pushing somewhere around 150 watts, RMS.
If moving the switch (to clean the contacts) doesn't do anything and adjusting/moving the controls for the low pass crossover doesn't help, it's likely that you have at least one bad solder connection. They will appear as little rings in the solder joints. If you have any that look like that, you need to resolder them, unsolder them and then resolder them again. Simply resoldering them once may leave a layer of oxide that will cause the connection to fail again.

This is VERY common on budget-brand amplifiers that use single sided boards.
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