Tekko said:Nice heatsink for the moduleYUCK its ugly original
Your refurbished one is mutch nicer
thank you, thank you.
Note that the fins on the heat sink are not finished, i have broke my 1/8 endmill...
but anyway, it is already far better, i may leave it like that. No ones will go see inside
i will make it work on its own soon, i mean on its own with the power transfo , not with my external power supply. Who know, maybe something will blow on it again???
lets see....power cord is here...
Ok, cool, it works on its own for the first time in 3 years !!
Funny too, the oscillation is now 114khz...i may re-install a 100p cap on the opamp...
I can get 90v peak to peak on a 4 ohm resistance before cliping...
so it is close to 250wrms isnt it?? (45X.7)²/4=248wrms...
nothing smell bad, it start its oscillation right away and every time...good boy, good boy.
One concern on those fets and drivers: i have instaled 1w 5.6v zener on every gates, and also on every places that seemed bordeline.
So now, i will install it into its enclosure and make it play
boooom boooom !!
Funny too, the oscillation is now 114khz...i may re-install a 100p cap on the opamp...
I can get 90v peak to peak on a 4 ohm resistance before cliping...
so it is close to 250wrms isnt it?? (45X.7)²/4=248wrms...
nothing smell bad, it start its oscillation right away and every time...good boy, good boy.
One concern on those fets and drivers: i have instaled 1w 5.6v zener on every gates, and also on every places that seemed bordeline.
So now, i will install it into its enclosure and make it play
boooom boooom !!
Attachments
huuuuuuummmmmmmmmmmmmmmmmmmmmmmm
that what it does now. It played 5 minutes.
$%@$#%@?#%&$?#$%@%$!#$@!@#$@
I will disasemble it for the 423534897943 time, and see what happened.
WHAT A PIECE OF SHHHHHHHHHHHHHHHIT !!!!!!
Maybe i will get around a solution to its problem, like puting it into the trash can...or making a spin on it with my SUV.
that what it does now. It played 5 minutes.
$%@$#%@?#%&$?#$%@%$!#$@!@#$@
I will disasemble it for the 423534897943 time, and see what happened.
WHAT A PIECE OF SHHHHHHHHHHHHHHHIT !!!!!!
Maybe i will get around a solution to its problem, like puting it into the trash can...or making a spin on it with my SUV.
Pat,
that is exactly what mine did too... so what i did is replaced both schmitt inverters, and both mosfets, and double checked for solder bridges...and now it works great! (there is one small annoying issue, if you mute the system, before the auto-standby circuit kicks in, you do hear the line interference hum, but when you are listening to anything at all, you really can't hear it at all)
hope that gives ya a place to start with.
Oh one more note, when mine did the hummmmm the speaker was pulled inward like it was getting negative signal ... just an observation
Jer
that is exactly what mine did too... so what i did is replaced both schmitt inverters, and both mosfets, and double checked for solder bridges...and now it works great! (there is one small annoying issue, if you mute the system, before the auto-standby circuit kicks in, you do hear the line interference hum, but when you are listening to anything at all, you really can't hear it at all)
hope that gives ya a place to start with.
Oh one more note, when mine did the hummmmm the speaker was pulled inward like it was getting negative signal ... just an observation
Jer
yeah, mine is going inward too. If i play with the on/off switch, it start to rumble randomly quite loud, it send +vcc and -vcc alternatively at a rate of 15 hertz maybe. Strong enough to damage the woofer if leaved too long, that tells me that it is not the mosfets.
Oh man, i am mad, after all the precautions taken, all the new components (they are ALL new !!!!) , even some protective zener here and there, it is blown again...
But, since that i can open the module, it will be easy to find the defective component, and start from there...
Maybe, i said MAYBE i will work on it tomorrow.
Good night.
Oh man, i am mad, after all the precautions taken, all the new components (they are ALL new !!!!) , even some protective zener here and there, it is blown again...
But, since that i can open the module, it will be easy to find the defective component, and start from there...
Maybe, i said MAYBE i will work on it tomorrow.
Good night.
My two cents:
While logic level mosfets were an easy fix in this situation, they aren't necessarily a good fix.
Hate me yet?
Vth on them is sooooooooo low, especially at operating temp (lower yet) they cannot tolerate much noise at the gate, and that includes the infamous Cdv/dt induced turn on. Anywhere near a volt on the gate will turn it on spurriously.
An RC snubber may help keep this down by slowing the dv/dt transition.
Since Jeremy's still works, Pat, take those Zeners off the gates! They can be the source of noise and ringing and.... boom.
Really they won't protect it from anything anyway, the gate can't be driven too high by the "regulated" driver, the zener can't protect it from spurrious turn on either via noise or via Cdv/dt .. it's just going to cause you problems.
If you still have problems, a bad band aide fix would be a small cap (100p?) from gate to source, this will both slow down turn on and dv/dt, and help bypass any noise at the gate.
I would start with removing the zener though.
Then give it a real thorough and abusive test with the real supply and everything before you put it all together.
While logic level mosfets were an easy fix in this situation, they aren't necessarily a good fix.
Hate me yet?
Vth on them is sooooooooo low, especially at operating temp (lower yet) they cannot tolerate much noise at the gate, and that includes the infamous Cdv/dt induced turn on. Anywhere near a volt on the gate will turn it on spurriously.
An RC snubber may help keep this down by slowing the dv/dt transition.
Since Jeremy's still works, Pat, take those Zeners off the gates! They can be the source of noise and ringing and.... boom.
Really they won't protect it from anything anyway, the gate can't be driven too high by the "regulated" driver, the zener can't protect it from spurrious turn on either via noise or via Cdv/dt .. it's just going to cause you problems.
If you still have problems, a bad band aide fix would be a small cap (100p?) from gate to source, this will both slow down turn on and dv/dt, and help bypass any noise at the gate.
I would start with removing the zener though.
Then give it a real thorough and abusive test with the real supply and everything before you put it all together.
Hey !!, i am supposed to be in my bed...
Well, i have removed the zeners on the mosfets before final installation, the only remaining are on the vcc of the 74ac14...but the mosfets are fine for now, i have tested them already.
One concern is about the absence of shift level. The opamp output is simply connected to a small cap and goes to the input of one driver. The input clamp curent of the schmitt trigger is 20ma.
Figure that when the opamp is at its +vcc, that means +15vcc, added with the -92vcc rail, that makes 107v before the cap C2 gets discharged...and the better case, when opamp is at -15v and if the cap is discharged...that gives a difference of around 75v...i know, there is a resistance in series (r3), wich is a 1k i think, so that makes in the worst case 107v/1k=107ma direct current applied to the gate at pin 5 of the lower rail driver and better case 75/1000=75ma. hummm, i am wondering. It is far beyond the 20ma capability of the driver !! Anyway, i will remove all suspicious components and test them carefully. What fears me is that when i will power it up tomorrow, i will not be surprised that it will work !!
Well, i have removed the zeners on the mosfets before final installation, the only remaining are on the vcc of the 74ac14...but the mosfets are fine for now, i have tested them already.
One concern is about the absence of shift level. The opamp output is simply connected to a small cap and goes to the input of one driver. The input clamp curent of the schmitt trigger is 20ma.
Figure that when the opamp is at its +vcc, that means +15vcc, added with the -92vcc rail, that makes 107v before the cap C2 gets discharged...and the better case, when opamp is at -15v and if the cap is discharged...that gives a difference of around 75v...i know, there is a resistance in series (r3), wich is a 1k i think, so that makes in the worst case 107v/1k=107ma direct current applied to the gate at pin 5 of the lower rail driver and better case 75/1000=75ma. hummm, i am wondering. It is far beyond the 20ma capability of the driver !! Anyway, i will remove all suspicious components and test them carefully. What fears me is that when i will power it up tomorrow, i will not be surprised that it will work !!
Hi, good morning. about the dv/dt of the fet, how about raising the gate resistor value? it is in mine 5 ohm , 2x 10 ohm parralel. I can cut easely one so i get 10 ohm...?
I didnt work on it yet this morning.
I will also try to implement the shift level like on the ir design, but i will need to add one more transistor to keep the logic signal the same. Looking at the AMI design again and again, the oscilating feedback is capacitive coupled by the infamous C2, and takes a lot of stress imho. Since its value is very small, there is all chances in the world that it can be already charged when it should not, hence the very bad turn-on scheme, what do you think? making it with transitor and direct coupled will help to start it, isnt it?
lets take a cofee.
I didnt work on it yet this morning.
I will also try to implement the shift level like on the ir design, but i will need to add one more transistor to keep the logic signal the same. Looking at the AMI design again and again, the oscilating feedback is capacitive coupled by the infamous C2, and takes a lot of stress imho. Since its value is very small, there is all chances in the world that it can be already charged when it should not, hence the very bad turn-on scheme, what do you think? making it with transitor and direct coupled will help to start it, isnt it?
lets take a cofee.
The design sucks eh ?Pat
Are you using the original board that you scraped off all the potting material from? If you are, did you by chance check to make absolute certain that there weren't any broken traces before resoldering the components? I did that with mine and did find one trace that had a break in it so I was able to repair that before I stuffed anything to it. Perhaps that is why sometimes yours works, and sometimes it doesn't?
Just a thought
LOL one more thing, I might be doing this all over again. I located another blown sub within an hour from my home and it has a similar problem.... for 26 bucks I might just have to do all this over again!!!!
Jer
Are you using the original board that you scraped off all the potting material from? If you are, did you by chance check to make absolute certain that there weren't any broken traces before resoldering the components? I did that with mine and did find one trace that had a break in it so I was able to repair that before I stuffed anything to it. Perhaps that is why sometimes yours works, and sometimes it doesn't?
Just a thought
LOL one more thing, I might be doing this all over again. I located another blown sub within an hour from my home and it has a similar problem.... for 26 bucks I might just have to do all this over again!!!!
Jer