This amp has 3 caps per reg.
One cap is in parallel with the zener. If it were faulty, it could only make the regulator output voltage low or noisy.
The second and third caps are connected between the regulator's output terminal (the transistor's emitter) and ground. If they were faulty, they could also make the output of the regulator low or noisy (because they weren't stabilizing the voltage as they should). If they were pulling the output down, the transistor would be damaged due to excessive current flow.
Pull the regulator transistor and check it out of the board. Check it to make sure it's not open, shorted or leaking (electrically). If you're not sure how to check it, let me know.
Check the zener while the transistor is out of the board. If the zener is open, the regulator output would be higher than normal.
The attached photo shows a basic discrete regulator without the capacitors.
One cap is in parallel with the zener. If it were faulty, it could only make the regulator output voltage low or noisy.
The second and third caps are connected between the regulator's output terminal (the transistor's emitter) and ground. If they were faulty, they could also make the output of the regulator low or noisy (because they weren't stabilizing the voltage as they should). If they were pulling the output down, the transistor would be damaged due to excessive current flow.
Pull the regulator transistor and check it out of the board. Check it to make sure it's not open, shorted or leaking (electrically). If you're not sure how to check it, let me know.
Check the zener while the transistor is out of the board. If the zener is open, the regulator output would be higher than normal.
The attached photo shows a basic discrete regulator without the capacitors.
Attachments
would I check the regulator transistor the same as I would test any npn or pnp transistor?I believe the transistor is pnp. The number on it is a1220a and I'm thinkin it is the same as a KSA1220A.I can't remember which meter lead goes on the first and second legs but I do remember that when they are oriented correctly the transistor should only read resistance in one direction if it is working properly.If its different than this please let me know Perry and thanks for the help you give whenever I have a question.
The PNP transistor is a KSA1220A.
The transistor is a standard BJT type transistor and you check it just as you would any other BJT. The pin configuration is reversed (ECB) compared to the higher power to-220 case transistors (BCE).
With the black lead on the base, the meter should read ~0.65v (with the meter set to 'diode check') when you touch the red lead to the other two leads. It should read open when you have the red lead on the base and touch the black lead to the other two leads. There should be no continuity/leakage (it should read as open) between the emitter and collector. For a more thorough test, switch to resistance when checking for leakage between the collector and the emitter.
You can check it on resistance. Instead of reading near 0.65v, it's going to read near 2 mega-ohms.
This must be done with the transistor removed from the board.
The transistor is a standard BJT type transistor and you check it just as you would any other BJT. The pin configuration is reversed (ECB) compared to the higher power to-220 case transistors (BCE).
With the black lead on the base, the meter should read ~0.65v (with the meter set to 'diode check') when you touch the red lead to the other two leads. It should read open when you have the red lead on the base and touch the black lead to the other two leads. There should be no continuity/leakage (it should read as open) between the emitter and collector. For a more thorough test, switch to resistance when checking for leakage between the collector and the emitter.
You can check it on resistance. Instead of reading near 0.65v, it's going to read near 2 mega-ohms.
This must be done with the transistor removed from the board.
the regulator transistor checks out fine.Theres no leakage from the collector to the emitter and it reads exactly as you described with the meter set to diode check.The small diode underneath the capacitor that keeps dying is open.Does the regulator transistor need to be replaced as well?Or should it be ok as long as I replace the capacitor and the diode?I'm not exactly sure how to read this diode.Its very tiny and has only a few numbers on it.With the black stripe pointing downward it reads 91- .pointed the other way it reads - 16 .I'm assuming that a 1N goes in front of one of those.
Help please
Hello, I'm jacking this old thread instead of starting a new one. I've got a mrv1000 that needs help. I got it with the right channel out. I know enough now to get myself in trouble, but I'm trying to learn as I go. I see the IRFZ44's had been replaced before so I took them out and found them to be bad. I replaced them with some IRF540's I had around. Hooked it up and it worked! Then, not sure if coincidence or not, but I was fiddling with the RCA's and poof! So I Replaced the RCA Jacks, Read some posts, Checked the Gate Resistors, All 4 were in spec of 100 ohms. I replaced the IRFZ44's with new IRFZ44's. I didn't see anything else that looked suspicious. I hooked it up and the amp ran good for about 10-15 minutes then the 1st leg on the second fet got red hot and was smoking! I pulled power and obviously found the fets to be bad again. I'm now at a what next situation and would like some help. Maybe some things to check, other threads to read, anything really. Thanks.
Hello, I'm jacking this old thread instead of starting a new one. I've got a mrv1000 that needs help. I got it with the right channel out. I know enough now to get myself in trouble, but I'm trying to learn as I go. I see the IRFZ44's had been replaced before so I took them out and found them to be bad. I replaced them with some IRF540's I had around. Hooked it up and it worked! Then, not sure if coincidence or not, but I was fiddling with the RCA's and poof! So I Replaced the RCA Jacks, Read some posts, Checked the Gate Resistors, All 4 were in spec of 100 ohms. I replaced the IRFZ44's with new IRFZ44's. I didn't see anything else that looked suspicious. I hooked it up and the amp ran good for about 10-15 minutes then the 1st leg on the second fet got red hot and was smoking! I pulled power and obviously found the fets to be bad again. I'm now at a what next situation and would like some help. Maybe some things to check, other threads to read, anything really. Thanks.
go from the center leg of the dual emitter resistors to each individual outer leg. You'll have to make sure you get good contact and stay stable with your meter leads for a few moments to get accurate readings on them. I would check your output transistors to see if one is shorted or leaky as well.
Should just start a new thread but, the resistors for the outputs? They don't go bad often and are hard to read with meter because ohms are so low. Some run an output into each end and sum in the center pin that would go to speaker terminal, or have two inputs one end and out the single pin on other end. You have some other problem with the alpine. The resistors could still be off enough to cause a problem according to what people say, there might also be pull down resistors upstream of the gate resistors you should check. Was it drawing a lot of current? What do you have at the outputs when you run it? Should start them with a 10A fuse or so. I just did one put all PS fets in one side, all resistors, seemed to work fine but have not used it yet. The one I have each channel is its own amp pretty much.
Test the larger outputs, none should have low resistance between any legs. Most of the time they short but not always.
Test the larger outputs, none should have low resistance between any legs. Most of the time they short but not always.
Thanks for the replies. I pulled the dual emitters off both sides to do comparisons. I didn't have my good meter at home so I'll have to check them today. The reason I ask about them is because I remembered that the first time I ran it with the temporary fets and wiggled the rca's, I saw a flash in one of them, I thought. Anyways, I will check the other resistors down the bad side and see if any are bad or leaking. Yes this amp is also like 2 amps in one. One amp per side basically. Kinda nice, because I can compare alot of things from the good side to the bad side. I have to wait till my irfz44's get here to run it again, but I have things to check out till then. Thanks again.
You might play around and check some other obvious stuff, like for shorted rail caps and bad diodes shorting to ground. You know the PS is blowing so could be it is being asked to make too much power (short/etc after PS/bad outputs/caps), or PS is not working right like driver has issue/gate resistors/etc. If you limit power to it when you fire it up, and only run short time then check for heat, you may be able to find where power is going and what is hot/etc. Get a big 2 ohm resistor and use a small fuse before amp like 10A.
Thanks Jol, I got good readings on the dual emitters, all were .1 if I sat still. The gate resistors checked ok. I will be going down the line tonight and checking the other transistors and diodes. My fets should be here in a couple days so if I don't find anything between now and then, I'll install them and hook up a resistor and small fuse on the power side and see what gets hot. Been looking for places to get parts incase I need them. The one source I have doesn't carry some of the resistors I see on the board. Maybe they won't be bad. Thanks for the input. Have a good day.
I bought two for a friend of mine, and I have a 1002 that is nearly the same thing inside but have not tried it yet. I have to repair the power terminals first, had to put a new PS in one side to get it going. There is only 420w on my four 12s right now and they bump, so 600 ought to do something. Think they are 600 x1 at the newer 14v ratings. Thinking of using it on midbass actually and a MRD-500 on subs....but its larger in size and watts than the class d 500...? lol, oh well.
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