Hifonics Pluto Possible Zed Audio Negative Rail Short locate Journey

Hifonics Pluto Possible Zed Audio Negative Rail Short locate Journey

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00:00
[Music] thank you for tuning in to ellensburg amplifier repair and service today i have a amplifier board that's labeled on the other side pluto so i think it's a maxonix possible z audio board just a 2 channel amplifier that
00:32
is presenting itself with a protection condition which has been kind of a challenge to find um it's using the irfc 44 vs on the power supply it's using the bd9 12s and the bd911s on the output there's no shorts in the audio pre-driver section here and so i figured i would just start doing some probing around on this board
01:13
to determine if i can find this area that's got a short in it so when i try to start it the 44 vs would they would heat up not significantly but they would get warm and then would go into protection so that tells me there's a short on the output and i've already tested uh the bd output transistor so there's no shorts there i've checked the bias transistors no
01:48
shorts so what i started doing was checking the resistance of the plus minus rails here and when i was probing the rails like and something's very strange about the way this is responding like there's a there's a short somewhere that's discharging this rail quite rapidly so what i do is i follow i
02:25
follow the output of the rectifier and while this was on the scope the positive rail voltage would build nice and then fall pretty steady but the negative rail would jump down real quick and then jump right back up so that told me there was a short in the negative rail so i follow the negative rail here and i get to the rail capacitors so here's the positive rail capacitor which is responding the way that
03:05
i was seen when i was checking the resistance between between the positive and negative rail voltages at the rectifier so there's the positive capacitor and here's the negative capacitor so you'll see here the negative rail capacitor is reading 14.4 ohms one way and 10.94 ohms the other so it could be a shorted capacitor which based on the age of this board could
03:44
could be likely or it could be i do have a single trace here that runs off to the uh that is going to be a yeah it runs off to resistor right here which is reading 4k or 400 ohms let me get the value of that resistor here so it's red yellow brown bust out my little color wheel here i don't have these memorized that's way too much information red yellow
04:30
brown so 240 ohms so that's not where i'm getting my that's not where i'm getting my short so i'm suspecting this capacitor right here to have a short across it 14 ohms on the negative rail capacitor and then we have well now our positive rail capacitor is charged so it's not showing let me see if i can reverse it here and we'll get a reading on that there we go so
05:12
and we're up in the 2 to 3k 4k on the positive rail capacitor so i'm thinking it's probably about time to remove this negative rail capacitor test that and see if that's my culprit so let me remove that and i'll be right back with you alright so i removed the two rail capacitors and i was still showing a 10 ohm short between the
05:46
secondary common and the negative rail so what i did is i eliminated all the paths on the negative rail that potentially could be leading back to the pre-drive area and as i was going back i just didn't see that 10 ohm short none of the transistors were shorted um if you watched my previous videos i like to use resistance quite a bit to uh find those low
06:21
value shorts and components and then i disconnected the resistor going back to pin two of the tl594 so what i did is i traced back that negative rail all the way back to the tl594 pin two and i lifted the resistor there and i still showed the 10 ohm short uh it's like it's like chasing a ghost
06:54
until you make it so far back you're back to the transformer well come to find out the rectifier the rectifier and memory uh how is noted that i was showing that quick spike on the negative rail and then dropping back to zero on the negative rail so i knew the issue was in the negative rail so if you take a resistance value of this rectifier there's my short for you so
07:30
this rectifier has a short across the ac input side and the negative output so let's uh let's see we read here in diode mode oh yeah 106. so that just goes to show that you just need to hunt down a short eliminate its path until you eventually get to the path where it shows itself so
08:24
i need to figure out if one of these is even still available so hopefully i can find another one so i'm unable to fire this up for you guys and show you the completion of this board uh just due to the fact that this rectifier's probably got to be hunted down somewhere hopefully someone has one and uh i will see what i can do here so just as a reference this is the mb
09:01
102f rectifier so what i'll do is i'll we'll look for one online and let's even get one if not i'll let the customer know that uh this rectifier is uh damaged and uh let them know that it'll be back on the road form so i do thank you guys for watching please like and subscribe like repair content i will release videos as just as much as possible and answer any questions that come around thanks for watching catch on the next
09:33
one

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