Very good, a pleasure to be of help to you
Someone else sent me a email about gain testing transistor and how my rants had saved him in a 12 KW amp rebuild. he said he found 5 devices in a tube that had nothing in common with the others, and that if had used them he felt sure it would have been a disaster.
Glad this is all working out for you... have a good one...C
Someone else sent me a email about gain testing transistor and how my rants had saved him in a 12 KW amp rebuild. he said he found 5 devices in a tube that had nothing in common with the others, and that if had used them he felt sure it would have been a disaster.Glad this is all working out for you... have a good one...C
Depends on manufacturing standards the amp was built with, but +&-5% is typical. My Adcom amps use +&-3% matched mosfets. If all the resistors near by are +&- 5% then the best match you could hope for would be +&- 5% just because of the resistors and capacitors in circuit causing a +&-5% possible deviation.
That voltage test I attached shows how to read the transistors turned on in circuit. If you read each individual resistors Voltage drop and they are not within the tolerance range of the resistors itself say +&-5%, then you might see the amp again real soon. The match can't be any better then the surround components. So if the those sand block resistors are +&-5% then the best you could hope for is +&-5% because you must take into account for the resistors not being any closer spec which can throw measurements off by their tolerance.
I see thanks, makes sense. In my case all of the resistors I looked at are 5%. I'm pretty sure that both the old emitter resistors are 5% too, the new ones are 5%.
One more question. Do you have any tips on how to properly\safely set the gains on the amp when it's back in the car, as I mentioned before I don't really have any special equipment for this purpose.
One more question. Do you have any tips on how to properly\safely set the gains on the amp when it's back in the car, as I mentioned before I don't really have any special equipment for this purpose.
If you google search car audio gain setting it should come up on several audio forums describing how to do this part of an amp install. I know that the Phoenix phorum had instructions and a simple download of test tones you could use, or at least they did have it at one time. Others like DIYMA might also have it, and maybe a few other of the car audio forums like the 12 volt.com etc...
Its not as simple as you may think but it does not require much more then a test cd of constant signals , white and pink noise and test tones and those can be downloaded from the web in several places, and burned to a normal computer Cdrom and played back with track loop set so it stays on as long as you need it to be while you doing your measurements and readjustments to you gains. Other the that all you will need usually is a good True RMS AC voltmeter like a Fluke 87 or similar to measure the amps output voltages to the speakers. I also like to use a SPL meter because all speakers do not exhibit the same output with common input < efficiency differences in common drivers >.
Next to wiring a car up safely, and equipment install, the final alignment and balancing is the biggest time sink of the whole job. The Ac voltmeter method is just one, another is by using a real time spectrum analyzer with display on a screen and appropriately placed high quality audio microphones < very expensive gear way > And it does not hurt to actually look for and find what is called a "Good Ear" to do the alignment for you < not all folks hear the same so having someone with exceptional skills in final system alignment < a good ear> with proper gear is always a big plus. But again this in not cheap as they usually charge by the hour to do such things, at least they use to anyway, its been a while since I had anyone touch my gear so maybe they flat rate it now, all depends on where you are located and the popularity of car audio in your area.
Hope this helps some on your quest for high SQ in a vehicle environment. It can be a holy grail chase in some vehicles requiring time alignment and 1/3 octave EQing just work around the typical problems a vehicle can pose to high sound quality....Good luck my friend...
Thanks, that's pretty much what I was expecting.
So just an update. After putting the amp back into the car and hooking everything back up I was greeted with the exact same problem, only it was even louder this time. To cut a long story short I tracked the problem down to what I think is the main culprit in this mess: I think it's the toggle switch for LPF/flat/HPF setting! Playing around with it in HPF causes loud pops and crackling, After turning off the amp, and setting it to flat, the noise is completely gone.
So I wonder, can it be just a faulty switch with a bad contact or could it be something else? You can picture the noise as when you plug in your headphones and rotate the connector in the socket to where it loses contact and sort of crackles. Same noise here only louder. I tried playing with the gain pot to see if the level of this crackling would go up/down, but it seemed to stay the same no matter where I set the gain pot at, and it's important to note that the noise is there even if I disconnect the RCA cable, so it's not coming from the HU.
One more thing, the gain pot on the other side seems to also have a similar problem with having bad contact and 'dead areas'. I can turn it up a bit and the sound level will go down or even disappear altogether, then wiggle it in place and the sound comes back. Should I just order some new pots and switches and replace them while I'm at it?
So just an update. After putting the amp back into the car and hooking everything back up I was greeted with the exact same problem, only it was even louder this time. To cut a long story short I tracked the problem down to what I think is the main culprit in this mess: I think it's the toggle switch for LPF/flat/HPF setting! Playing around with it in HPF causes loud pops and crackling, After turning off the amp, and setting it to flat, the noise is completely gone.
So I wonder, can it be just a faulty switch with a bad contact or could it be something else? You can picture the noise as when you plug in your headphones and rotate the connector in the socket to where it loses contact and sort of crackles. Same noise here only louder. I tried playing with the gain pot to see if the level of this crackling would go up/down, but it seemed to stay the same no matter where I set the gain pot at, and it's important to note that the noise is there even if I disconnect the RCA cable, so it's not coming from the HU.
One more thing, the gain pot on the other side seems to also have a similar problem with having bad contact and 'dead areas'. I can turn it up a bit and the sound level will go down or even disappear altogether, then wiggle it in place and the sound comes back. Should I just order some new pots and switches and replace them while I'm at it?
In most cases, when you have a dirty switch or pot, the audio drops out and may have a slight click as the contacts intermittently make/break. If there is a loud pop, you should check all of the op-amps to see if any have significant DC voltage on their output pins.
Contact cleaner may help get the controls clean.
Contact cleaner may help get the controls clean.
Right, I didn't think of that, thanks. There usually always a simpler and quicker solution I guess, if it is indeed a dirty contact.
One more 'interesting' thing I found is that my rear set of speakers (Morel Tempo Coax 6x9), which is a 2-element unit and comes with a crossover box. I checked the resistance across the leads that go into the amp's outputs before plugging them in, and one read 4.1 ohms, which is OK and the second one read 5.1ohm. This seems like a pretty bad deviation from what it should be and I think that the side with the higher resistance isn't as loud as the second speaker. Is there any suggestions on what could be the problem there?
One more 'interesting' thing I found is that my rear set of speakers (Morel Tempo Coax 6x9), which is a 2-element unit and comes with a crossover box. I checked the resistance across the leads that go into the amp's outputs before plugging them in, and one read 4.1 ohms, which is OK and the second one read 5.1ohm. This seems like a pretty bad deviation from what it should be and I think that the side with the higher resistance isn't as loud as the second speaker. Is there any suggestions on what could be the problem there?
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@The Coolest,
According to Online and free search for integrated circuits and semiconductors replacements, equivalents and substitutes database - Powered by ElectroNika Software you can replace IRZ46N with any of the following parts:
2SK2049
BUK456-50
BUK556-60
BUZ100
The site doesn't mention STP80NF as a replacement part.
You can check the complete information source at N-channel-FET.. IRFZ46N Replacements / Equivalent parts / Substitutes, N-channel-FET.. Cross reference, N-channel-FET.. Datasheet PDF
Hope it helps,
James
According to Online and free search for integrated circuits and semiconductors replacements, equivalents and substitutes database - Powered by ElectroNika Software you can replace IRZ46N with any of the following parts:
2SK2049
BUK456-50
BUK556-60
BUZ100
The site doesn't mention STP80NF as a replacement part.
You can check the complete information source at N-channel-FET.. IRFZ46N Replacements / Equivalent parts / Substitutes, N-channel-FET.. Cross reference, N-channel-FET.. Datasheet PDF
Hope it helps,
James
I went back and rechecked the resistance on the rear speakers again today, and everything read fine now. Either there was a bad contact, which was sorted once I unplugged the elements from crossover or maybe I couldn't get a good contact with the probes when I was measuring the resistance before. In any case the resistance is fine and there's no problem.
I decided to leave the toggle switch and pot be for the moment, as I didn't feel like taking the amp out of the car and disassembling it all over again. But I will probably end up doing it sometime in the future.
One last thing that remains is to set the gains on it properly in conjunction with my HU. I'm planning to go to a car audio meeting on Saturday and someone's bringing a scope, this should make it pretty simple to setup without getting distortion.
@jameshalo
Thanks, but I've already replaced all the parts, you can check this post:
http://www.diyaudio.com/forums/car-...s-lightning-audio-b300-4-a-2.html#post3873789
I decided to leave the toggle switch and pot be for the moment, as I didn't feel like taking the amp out of the car and disassembling it all over again. But I will probably end up doing it sometime in the future.
One last thing that remains is to set the gains on it properly in conjunction with my HU. I'm planning to go to a car audio meeting on Saturday and someone's bringing a scope, this should make it pretty simple to setup without getting distortion.
@jameshalo
Thanks, but I've already replaced all the parts, you can check this post:
http://www.diyaudio.com/forums/car-...s-lightning-audio-b300-4-a-2.html#post3873789
There is no practical way (for most systems/users) to set the gains where there is no chance of driving the system into distortion. About the best that you can do is set them so that you can get the amps to clipping on the types of music you normally listen to with the setting that you normally use at 3/4 volume on the head unit. From there, you have to listen for distortion and reduce the volume when you hear the distortion (if you want to avoid driving the amps into clipping). The scope is good to help you determine what the clipped signal sounds like (relate the visibly clipped signal to what you hear).
Hi guys, I'm back with a small update and a couple of questions I hope you can help me with.
I've been able to set gains properly using a portable scope. It seems that the volume is much lower now at the same HU setting, but then I have a finer control, and it can still be loud enough when I want it.
All in all I'm satisfied with how the amp works now, but there are two things I wanted to ask you guys about.
1) Some times there's a very strange behavior from the amp, the front-left channel is very loud (louder than normal) and the other 3 channels are very quiet (quieter than normal). Turning the amp on and off, playing with volume, balance, the input RCAs on the amp and the EQ switches doesn't change anything. I can then return to the car several hours later or the next day and everything works fine without a hitch. Any ideas what could cause such a problem to occur? Is it possible that some component is shorting out on the case? (I reused the old thermal pads, but they seemed to be in an OK shape)
2) This 2nd issue is a little hard to describe and could be subjective but the depth of the sound seems to be kind of lacking until I hit a rather high volume which isn't very nice for long periods of time. I can't recall if there was such a problem before swapping the components, but at higher volume the sound seems much clearer/crispier/fuller and all-in-all nicer to listen to, but it is too loud for normal listening. At lower volume the only word to describe the sound is flat.
I'm using the Morel Tempo 6 (6") in the front and Morel Tempo Coax 6x9" in the rear. No other components (such as subwoofers or other speakers) are installed in the car.
I've been able to set gains properly using a portable scope. It seems that the volume is much lower now at the same HU setting, but then I have a finer control, and it can still be loud enough when I want it.
All in all I'm satisfied with how the amp works now, but there are two things I wanted to ask you guys about.
1) Some times there's a very strange behavior from the amp, the front-left channel is very loud (louder than normal) and the other 3 channels are very quiet (quieter than normal). Turning the amp on and off, playing with volume, balance, the input RCAs on the amp and the EQ switches doesn't change anything. I can then return to the car several hours later or the next day and everything works fine without a hitch. Any ideas what could cause such a problem to occur? Is it possible that some component is shorting out on the case? (I reused the old thermal pads, but they seemed to be in an OK shape)
2) This 2nd issue is a little hard to describe and could be subjective but the depth of the sound seems to be kind of lacking until I hit a rather high volume which isn't very nice for long periods of time. I can't recall if there was such a problem before swapping the components, but at higher volume the sound seems much clearer/crispier/fuller and all-in-all nicer to listen to, but it is too loud for normal listening. At lower volume the only word to describe the sound is flat.
I'm using the Morel Tempo 6 (6") in the front and Morel Tempo Coax 6x9" in the rear. No other components (such as subwoofers or other speakers) are installed in the car.
It's most likely that one channel is going high and the others are remaining the same but seem lower.
You need to be able to recreate the fault but you first need to get a reference. You need to drive a signal with a fixed/known level (0.1v AC should be OK). You then need to measure the AC voltage on R151, R251, R351 and R451.
This needs to be done when the amp is working properly. It should probably also be done with no speaker wires connected to the amp.
When the amp malfunctions, you need to drive the reference signal into the amp again and re-check the voltage on those resistors again. If the voltage on all resistors is equal when the output is unequal, the problem is in the amplifier section or possibly in the muting circuit. If the voltage becomes unequal on those resistors, the problem is in the preamp section.
Measure on the side of the resistor connected to the electrolytic capacitor.
You need to be able to recreate the fault but you first need to get a reference. You need to drive a signal with a fixed/known level (0.1v AC should be OK). You then need to measure the AC voltage on R151, R251, R351 and R451.
This needs to be done when the amp is working properly. It should probably also be done with no speaker wires connected to the amp.
When the amp malfunctions, you need to drive the reference signal into the amp again and re-check the voltage on those resistors again. If the voltage on all resistors is equal when the output is unequal, the problem is in the amplifier section or possibly in the muting circuit. If the voltage becomes unequal on those resistors, the problem is in the preamp section.
Measure on the side of the resistor connected to the electrolytic capacitor.
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